This study demonstrates for the first time, to the best of our knowledge, that femtosecond laser-induced periodic surface structures (LIPSSs) enhance diamond’s visible-light transmittance. Using cylindrical-lens-shaped beams for high-speed scanning and secondary defocused low-energy laser treatment, uniform nanogratings with a period of 105 nm (12 µm × 24 µm) were fabricated within 3 s. Optimized scanning speeds and pulse energies improved structural quality, achieving up to 10% transmittance enhancement at 625–750 nm. This approach offers a novel strategy for anti-reflective diamond optoelectronic devices.

A novel fabrication method for a 32-channel image slicer within the China Space Station Telescope (CSST) integral field spectrograph (IFS) is proposed, addressing challenges in multi-channel micro-slicer manufacturing. Our approach employs ladder stacking, polishing, and reverse stacking, combined with the Ritz method and blade crack propagation theory, to optimize molecular bonding and minimize deformation. This approach simplifies fabrication while ensuring high imaging quality, thereby meeting the requirements of CSST-IFS. This study advances precision optical instrument manufacturing and provides valuable insights for its future developments.

Y-junction photonic power splitters are essential in photonic integrated circuits. In this paper, a tunable Y-junction splitter is introduced using a standard silicon-on-insulator platform. It features a single-point control mechanism of both the turnability of power splitting ratios and the non-volatility with optical phase change materials (O-PCMs). This nonvolatile Y-junction splitter has a broadband of 350 nm (from 1300 to 1650 nm) with an about 0.7 dB low insertion loss. Using the direct binary search (DBS) inverse design algorithm, a circular point was identified to fill the phase change material Sb2S3 within the coupling area of the Y-junction photonic power splitter. Six example power splitting ratios of 1.86, 1.70, 1.50, 1.34, 1.21, and 1.14 were realized under single-point control using phase changes at 1550 nm with a 0.35 dB low insertion loss. Furthermore, we also implemented a five-stage cascaded array, with the final stage consisting of 16 Y-junction splitters. These results are useful for significantly simplifying the control of photonic circuits.

This study presents a laser-based technique for fabricating nano-holes with tunable axial morphology on fused silica using ring-lens-tailored Bessel beams. Unlike conventional axicon-based Bessel methods, this approach effectively controls the beam’s axial intensity peak by simply adjusting the ring-lens radius (R). By combining theoretical simulation and experimental validation, we demonstrate that the nano-hole morphology can be precisely tuned by modulating the beam’s initial energy peak. A taper entrance can be formed, with the taper angle effectively controlled within 52° by adjusting R from 1.25 to 2.50 mm. When R exceeds 2.50 mm, the axial energy distribution becomes uniform and leads to the disappearance of the taper, resulting in a standard cylindrical hole and offering a clear process window for controlling the nano-hole morphology. This single-pulse ablation method advances precision nano-manufacturing by enabling the efficient fabrication of customized nano-holes, with potential applications in photonics, microfluidics, and other nano-engineering fields.

Broadband, low-drive voltage electro-optic modulators are crucial optoelectronic components in the new-generation microwave photonic links and broadband optical interconnect network applications. In this paper, we fabricate a low-loss thin-film lithium niobate complementary dual-output electro-optic modulator chip with a 3 dB electro-optic bandwidth of 59 GHz and a half-wave voltage (Vπ) of 2.5 V. The insert-loss of the packaged modulator is 4.2 dB after coupling with polarization-maintaining fiber. The complementary dual-output modulator also shows a common-mode rejection ratio of 18 dB and a signal enhancement of 6.2 dB when adapted in microwave photonic links, comparable to commercial bulk lithium niobate devices.

A high-performance grating coupler (GC) operating at a wavelength of 1550 nm is proposed by utilizing the adjoint-based inverse design algorithm on a 220 nm silicon-on-insulator (SOI) substrate. The grating scheme offers several advantages, including simple structure, large minimum feature size (MFS), manufacturing friendliness, support for large-scale production and multi-project wafer (MPW) runs, etc., while simultaneously maintaining exceptional coupling performance and fabrication tolerance. The design process incorporates various fabrication constraints to satisfy the specifications of different foundry processes. The optimized GC demonstrates excellent coupling performance and 3 dB bandwidth within the MFS range of 60 to 180 nm. The simulated coupling efficiency (CE) of the GC with 130 nm MFS is -1.69 dB, whereas the experimentally measured CE of the fabricated GC using electron beam lithography (EBL) is -2.83 dB. Notably, the experimental CE of the GC with 180 nm MFS fabricated using 248 nm deep ultraviolet (DUV) lithography is -2.77 dB, representing the highest experimental CE ever reported for a single-layer etching C-Band GC supported by MPW runs fabricated on 220 nm SOI without utilizing any back reflector, multi-etch layer, or overlay. The manufacturing outcomes of the same GC structure employing different manufacturing processes are discussed and analyzed, providing valuable insights for the fabrication of silicon photonics devices.

Free-space diffractive neural networks (DNNs) have been an intense research topic in machine learning for image recognition and encryption due to their high speed, lower power consumption, and high neuron density. Recent advances in DNNs have highlighted the need for smaller device footprints and the shift toward visible wavelengths. However, DNNs fabricated by electron beam lithography, are not suitable for microscopic imaging applications due to their large sizes, and DNNs fabricated by two-photon nanolithography with cylindrical neurons are not optimal for visible wavelengths, as the high-order diffraction could induce low diffraction efficiency. In this paper, we demonstrate that cubical diffraction neurons are more efficient diffraction elements for DNNs compared with cylindrical neurons. Based on the theoretical analysis of the relationship between the detector area sizes and classification accuracy, we reduced the size of DNNs operating at the wavelength of 532 nm for handwritten digit classification to micrometer scale by two-photon nanolithography. The DNNs with cubical neurons demonstrated an experimental classification accuracy (89.3%) for single-layer DNN, and 83.3% for two-layer DNN with device sizes similar to that of biological cells (about 100 µm × 100 µm). Our results paved the pathway to integrate 3D micrometer-scale DNNs with microscopic imaging systems for biological imaging and cell recognition.

We implement Monte Carlo-based parallel ray tracing to achieve quick irradiance evaluation for freeform lenses with non-uniform rational B-splines (NURBS) surfaces. We employ the inverse transform sampling method to sample rays uniformly from the Lambertian light source and adopt the analytical form of the B-spline basis function to achieve fast surface interpolation. When performing parallel calculations for the intersections between the rays and the NURBS surfaces, we propose a parameter transformation method to avoid the parameters escaping from the defined range in the iteration process. Simulation results of two complex picture-generating freeform lenses show that our method is fast and effective.

In this Letter, we presented a flexible omnidirectional reflective film made of polymer substrates and multiple alternating layers of two chalcogenide glasses for full-angle CO2 laser protection. The structure parameters of the device were simulated for theoretical prediction of best device structure. The reflector was fabricated by alternate thermal evaporation of two chalcogenide glasses with large refractive index contrast. The reflectivity was greater than 78% at 10.6 µm. The flexible reflective film can provide an effective solution for full-angle CO2 laser protection of the moving targets, such as laser operators and mobile optical components, with potential applications for wearable laser protective clothing.

A multi-direction bending sensor based on spot pattern demodulation of a dual-hole fiber (DHF) is proposed. By using the interference and scattering in a DHF, the related multidirectional variations can be captured by the optical field. Furthermore, the multi-directional bending characteristics of the fiber are quantitatively described by the pattern of the output light spot, achieving multidirectional bending sensing. In addition, considering the subtle changes in the deformation patterns over time, a convolutional neural network (CNN) model based on deep learning is introduced for accurate recognition and prediction of the bending angle. The experimental results show that the sensor can perceive different bending angles in four directions. These outstanding results indicate that the multi-directional bending sensor based on dual-hole interference pattern decoding has potential applications in multi-directional quantitative sensing and artificial intelligence perception.

With different interactions between material and femtosecond lasers, two-dimensional (2D) and three-dimensional (3D) waveguide couplers, whose separation distances are fabricated in z-cut lithium niobate crystal by femtosecond laser writing, are reported. Experimentally and numerically, it is shown from results that the guidance is only propagating along TM polarization due to the Type I modification and holds equal splitting ratios, which are the same as power splitters at 632.8 nm. The propagation losses of 2D and 3D waveguide couplers exhibit better transmission properties than those of the previously reported Type I Y-junction waveguide splitters.

Plasmonics could provide compact and powerful solutions for manipulating light in deep-subwavelength dimensions, which is promising for a great range of nanophotonic technologies such as plasmonic rulers and sensors. However, the effective area of enhanced localized field induced by surface plasmon polaritons is typically restricted to the structural boundaries. In this work, we propose a method to generate high quality-factor extended electromagnetic fields via hybridizing the super-radiant state and the quasi bound state in the continuum of graphene metasurfaces. The coupling interaction involved operates as a three-level system with multiple sharp resonances immune to the polarization, which holds great promise for developing nanodevices with high sensing capacity in two dimensions.

The microresonator-based soliton microcomb has shown a promising future in many applications. In this work, we report the fabrication of high quality (Q) Si3N4 microring resonators for soliton microcomb generation. By developing the fabrication process with crack isolation trenches and annealing, we can deposit thick stoichiometric Si3N4 film of 800 nm without cracks in the central area. The highest intrinsic Q of the Si3N4 microring obtained in our experiments is about 6×106, corresponding to a propagation loss as low as 0.058 dBm/cm. With such a high Q film, we fabricate microrings with the anomalous dispersion and demonstrate the generation of soliton microcombs with 100 mW on-chip pump power, with an optical parametric oscillation threshold of only 13.4 mW. Our Si3N4 integrated chip provides an ideal platform for researches and applications of nonlinear photonics and integrated photonics.

In order to realize the ultrastrong absorption of graphene with electrical modulation properties, we designed a composite structure of graphene and parity-time (PT) symmetry photonic crystal, which is achieved by placing the graphene layer on the top layer of the PT symmetry photonic crystal. In this paper, the absorption properties of graphene and the electrical modulating properties of the structure were theoretically analyzed based on the transfer matrix method. The result shows that the proposed structure can achieve the absorption of 31.5 dB for the communication wavelength of 1550 nm; meanwhile, by setting the electric field intensity to ±0.02 V/nm, the absorption of graphene can be largely modulated to realize an electrically switchable effect, the modulation depth of graphene absorption can reach nearly 100%, and the operation speed is also close to 8.171 GHz. This investigation provides a novel approach to design graphene-based optoelectronic devices and optical communication devices.

Depressed cladding waveguides are fabricated in Pr:LiYF4 (YLF) crystal by femtosecond laser inscription following a helical scheme. With the optimized parameters, the propagation loss of the waveguide is around 0.12 dB/cm for multimode guiding. Under optical pumping with InGaN laser diodes at 444 nm, efficient waveguide lasers in the orange around 604 nm (π-polarized) are achieved with minimum lasing threshold of 119.8 mW, maximum slope efficiency of 16.6%, and maximum output power of 120.6 mW. Benefiting from their optimized performances, the waveguides produced in this work are promising for applications as compact orange laser sources.

It is well known that cats have fascinating eyes with various colors, such as green, blue, and brown. In addition, they possess strong night vision ability, which can distinguish things clearly even in a poor light environment. These drive us to reveal the secrets behind them. In fact, cats’ eyes can be considered as special lenses (which we would like to mimic by using a Luneburg lens). We make an analysis of the role of photonic crystals behind the lens and demonstrate that the integration of photonic crystals into Luneburg lens can be regarded as a retroreflector and greatly improve the light focusing intensity of the lens in a broad band of frequencies. This wonderful bioinspired phenomenon is expected to design more interesting and serviceable devices by combining photonic crystals with transformation optics.

We report the observation of second order Bragg resonance (2nd-OBG) produced by tilted fiber gratings (TFGs) fabricated using phase mask UV inscription. The theoretical analysis has revealed that the generation of high order Bragg resonance of gratings is induced by a square-shape refractive index profile, which is caused by over-saturated UV exposure. In the experiment, we have studied the TFGs with different tilt angles under over-saturated UV exposure, in which all gratings have showed the 2nd-OBR, and the larger tilt angle of the grating has the stronger 2nd-OBR. When the tilt angle of the grating is ∼45°, the Bragg resonance exhibits very strong polarization dependence, because the 2nd-OBR wavelength is located within the polarizing bandwidth of 45° TFG. Finally, we have demonstrated an erbium-doped fiber laser with >99.9% degree of polarization, and, by applying mechanical stretching on the grating, a wavelength tunable laser output has been achieved. The output laser shows ∼0.2 dB amplitude variation within 1 h continuous monitoring of the laser.

A micro-projection dynamic backlight for multi-view three-dimensional (3D) display is proposed. The proposed backlight includes a light emitting diodes (LEDs) array, a lenticular lens array, and a scattering film. The LED array, the lenticular lens, and the scattering film construct a micro-projection structure. In this structure, the LEDs in the array are divided into several groups. The light from each LED group can be projected to the scattering film by the lenticular lens and forms a series of bright stripes. The different LED groups have different horizontal positions, so these bright stripes corresponding to different LED groups also have different horizontal positions. Therefore, they can be used as a dynamic backlight. Because the distance between the LEDs array and the lenticular lens is much larger than the distance between the lenticular lens and the scattering films, the imaging progress will make the width of the bright stripes much smaller than that of the LEDs, and the pitch of the stripes is also decreased. According to the 3D display theory, the bright stripes with small width and pitch help to increase the number of views. Therefore, the proposed micro-projection dynamic backlight is very suitable for multi-view 3D display. An experimental prototype was developed, and the experimental results show that the micro-projection dynamic backlight can correctly complete the directional projection of the parallax images to form a 3D display.

In this study, an effective method is proposed for controlling a titanium foil surface’s wettability. A microholes array series is fabricated on the surface of titanium foil by a femtosecond laser under different laser energy and pulse number. The changes of the titanium surface’s morphology are characterized. When placed in a darkroom with high-temperature treatment and immersed in alcohol under UV irradiation, respectively, the femtosecond laser treated surfaces display switchable wettability. It is demonstrated that the changing between Ti-OH and Ti-O prompts the transformation between superhydrophilic and superhydrophobic. Compared with existing reports, the switchable wetting cycle is shortened to 1.5 h. The functional surfaces with switchable wettability have potential applications in oil–water separation and water mist collection.

A fiber-based source that can be exploited in a stimulated emission depletion (STED) inspired nanolithography setup is presented. Such a source maintains the excitation beam pulse, generates a ring-shaped depletion beam, and automatically realizes dual-beam coaxial alignment that is critical for two beam nanolithography. The mode conversion of the depletion beam is realized by using a customized vortex fiber, which converts the Gaussian beam into a donut-shaped azimuthally polarized beam. The pulse width and repetition frequency of the excitation beam remain unchanged, and its polarization states can be controlled. According to the simulated point spread function of each beam in the focal region, the full width at half-maximum of the effective spot size in STED nanofabrication could decrease to less than 28.6 nm.

Using compressive sensing for imaging has many applications, and it is an important branch of computational imaging. In this Letter, freeform surfaces are introduced in the hardware optical system design of a compressive sensing imager. The system works under the medium wave infrared band and realizes a 16× compression with a field-of-view of 7.5°×6°. Good imaging performance is achieved in both the entire system and the freeform objective optics. Compared with the system using all spherical lenses, the volume of the freeform system is about 1/3 smaller, and the total transmittance is about 56% higher, which shows the benefits of using freeform surfaces for compressive sensing and computational imaging.

To solve the issue of the contradiction between photovoltaic power generation and plant photosynthesis for sunlight demand, we propose a design method of multi-passband polymer multilayer optical structure. Using polycarbonate (PC) and polymethyl methacrylate (PMMA), two polymer materials with different refractive indices, the passband position and passband bandwidth are calculated and adjusted by the transmission matrix method and TFCalc software. A 450 nm, 660 nm, and 730 nm three-passband filter was realized by superimposing stacks of different band positions. The feasibility of the photovoltaic agriculture was confirmed by the power generation efficiency and the actual plant growth.

Optical fibers have been widely applied to telecommunication, imaging, lasers, and sensing. Among the different types of fibers, photonic crystal fibers (PCFs), also called microstructured optical fibers, characterized by air holes arranged along the length of fibers have experienced tremendous advance due to their unique advantages. They are regarded as a desirable platform to excite surface plasmon resonance (SPR) because of easy realization of phase matching conditions between the fundamental core mode and the plasmonic mode, which plays a critical role in miniaturization and integration of SPR sensors. In this mini-review, the current status of PCF sensors based on SPR is summarized. The theory of SPR is discussed, and simulation methods for PCF-SPR sensors are described. The important parameters including the refractive index detection range, resonance wavelength, and spectral sensitivity responsible for the sensing properties of PCF-SPR sensors are reviewed. The fabrication and the comparison of performances are also illustrated, and, finally, the challenges and future perspectives are outlined.

A straightforward, cost-effective scheme for fabricating multi-focus droplet lens arrays is proposed. Mini lenses can be rapidly produced by dripping liquid-state polydimethylsiloxane droplets on the square glass substrate. The focal length of the lenses can be precisely controlled by adjusting the mass of the droplet. A group of prepared mini lenses can be flexibly assembled in a three-dimensional printed mount. The lenses are tightly packed together, ensuring a high filling factor of the lens array. The lens array consisting of the mini lenses with a proper combination of focal length can capture images of interests at different depth.

Traditional optical domes are spherical, which have a large air resistance coefficient. In order to reduce the coefficient of air resistance, conformal optical technology was proposed, which used a streamlined design of the outer surface of the dome. However, conformal domes generate dynamic aberrations varying significantly with look angles in the field of regard (FOR). Thus, correcting the dynamic aberrations is the core task of conformal optics. This Letter presented a correcting method of dynamic aberrations based on the diffraction surface and anamorphic asphere surface. This method is derived from the arch corrector and can only be used on the Roll-Nod gimbal. For the seeker with a Roll-Nod gimbal, the arch corrector is replaced with a diffractive surface superimposed on the inner surface of the conformal dome. To correct astigmatism, which is the main aberration that needs to be corrected, anamorphic asphere surfaces are used in the imaging system. Compared with the arch corrector, this method can reduce the size of the correction element while retaining sufficient design freedom. Design results show that this method can well correct the dynamic aberrations in a larger FOR. With a simpler form in structure, this method can improve the reliability of conformal optical systems and promote the application of conformal optical technology.

Polarization aberration caused by material birefringence can be partially compensated by lens clocking. In this Letter, we propose a fast and efficient clocking optimization method. First, the material birefringence distribution is fitted by the orientation Zernike polynomials. On this basis, the birefringence sensitivity matrix of each lens element can be calculated. Then we derive the rotation matrix of the orientation Zernike polynomials and establish a mathematical model for clocking optimization. Finally, an optimization example is given to illustrate the efficiency of the new method. The result shows that the maximum RMS of retardation is reduced by 64% using only 48.99 s.

In this Letter, a Gabor superlens with variable focus is presented. This configuration uses tunable liquid lenses in the third microlens array of the Gabor superlens. By applying voltage, the radius of curvature of the micro-tunable doublet arrays changes, and the Gabor conditions are fulfilled at different focal planes. As a consequence, the magnification of the image at the focal planes changes, and a zoom effect is observed. The marginal depth plane for this system goes from 0.86 to 0.89 mm. The optical simulation, calculations, and results of the simulated optical system performance are presented.

A novel way to design arbitrarily shaped retro-reflectors by optics surface transformation is proposed. The entire design process consists of filling an optic-null medium between the input and output surfaces of the retro-reflector, on which the points have 180 deg reverse corresponding relations. The retro-reflector can be designed to be very thin (a planar structure) with high efficiency. The effective working angles of our retro-reflector are very large (from -80 deg to +80 deg), which can, in principle, be further extended. Layered metal plates and zero refractive index materials are designed to realize the proposed retro-reflector for a TM polarized beam.

In this Letter, we fabricate integrated metasurface of encoded dynamic phases and experimentally generate nonconventional Kagome-type lattices of no-second-order phase vortices. The thin metasurface acts analogous to an integration of three conventional optical elements, i.e., six pinholes located at the vertices of two concentric regular triangles of size ratio 1:2, six transparent discs of different thicknesses to introduce a total phase shift difference of 6π, and a Fourier lens with a focal length in the micro-scale. A Kagome lattice with the required vortex distribution is realized at the “focal” plane of the metasurface under illumination of the plane wave.

Freeform surfaces are difficult to manufacture due to their lack of rotational symmetry. To reduce the requirements for manufacturing precision, a design method is proposed for freeform reflective-imaging systems with low surface-figure-error sensitivity. The method considers both the surface-figure-error sensitivity and optical specifications, which can design initial systems insensitive to surface figure errors. Design starts with an initial planar system; the surface-figure-error sensitivity of the system is reduced during construction. The proposed method and another that is irrelevant to figure-error sensitivity are used to design a freeform off-axis three-mirror imaging system. Comparison of the sensitivities of the two systems indicates the superiority of our proposed method.

The diffraction of a dielectric microline pair is optimized by numerical simulations to generate an efficient focusing pattern with a micron-scale footprint. Microlines separated by 1.12 μm are fabricated by two-photon polymerization on a glass substrate, and their diffraction pattern is characterized by three-dimensional wide-field transmission microscopy. A line pair, having a width W=0.40 μm and a height H=0.80 μm, leads to diffraction-limited focusing in the visible spectrum. Depending on wavelength, its focal length, lateral resolution, and depth of focus are in the ranges of 0.8–1.3 μm, 0.22–0.44 μm, and 1.7–2.13 μm, respectively. Such a microlens based on the diffraction of only two subwavelength scatterers could be used for the design of miniature optical sensors with micron and sub-micron pixels.

Achromatic Talbot lithography (ATL) with high resolution has been demonstrated to be an excellent technique for large area periodic nano-fabrication. In this work, the uniformity of pattern distribution in ATL was studied in detail. Two ATL transmission masks with ～50% duty cycle in a square lattice were illuminated by a spatial coherent broadband extreme ultraviolet beam with a relative bandwidth of 2.38%. Nonuniform dot size distribution was observed by experiments and finite-difference time-domain simulations. The sum of the two kinds of diffraction patterns, with different lattice directions (45° rotated) and different intensity distributions, results in the final nonuniform pattern distribution.

The conventional optical system design employs combinations of different lenses to combat aberrations, which usually leads to considerable volume and weight. In this Letter, a tailored design scheme that exploits state-of-the-art digital aberration correction algorithms in addition to traditional optics design is investigated. In particular, the proposed method is applied to the design of refractive telescopes by shifting the burden of correcting chromatic aberrations to software. By enforcing cross-channel information transfer in a post-processing step, the uncorrected chromatic aberrations are well-mitigated. Accordingly, a telescope of F-8, 1400 mm focal length, and 0.14° field of view is designed with only two lens elements. The image quality of the designed telescope is evaluated by comparing it to the equivalent designs with multiple lenses in a traditional optical design manner, which validates the effectiveness of our design scheme.

We implemented a stitching swing arm profilometer (SSAP) test for the inner and outer regions of a large aspheric surface with a short arm. The SSAP was more capable of improving sampling density of surface and was less sensitive to system error, like vibration noise and air-table noise. Firstly, a calculation model was built to evaluate the sampling density of the SSAP test. Then, sensitivity to system noise was tested when different lengths of arm were used. At the end, an experiment on a 3 m diameter aspheric mirror was implemented, where test efficiency was promoted, and high sampling density was achieved.

Myopia has become a noteworthy issue due to the increasing use of our eyes. We propose a continuous power variation vision-training device based on Alvarez lenses with the power ranging from 10 D to +2 D. First, we introduce the principle of Alvarez lenses and the evaluation method of dioptric power and astigmatism. Then, we optimize the optical system described by Zernike polynomials. Finally, we analyze the distributions of dioptric power and astigmatism with the overall surface analysis and fields of view (FOVs) analysis. The results show that the optical performance of an optimized system can meet the requirement within a 40° FOV.

Calcium fluoride is widely used in optical lithography lenses and causes retardation that cannot be ignored. However, few studies have been conducted to compensate for the retardation caused by calcium fluoride in optical lithography systems. In this Letter, a new index based on orientation Zernike polynomials is established to describe the value of retardation. Then, a method of retardation compensation is described. The method is implemented by clocking calcium fluoride lens elements, and the optimal rotation angles are calculated using a population-based stochastic optimization algorithm. Finally, an example is provided to validate the method.

A rapid and cost-effective method for fabricating mini lens arrays is proposed. The lenses are made of silicone oil droplets and filled inside a polydimethylsiloxane (PDMS) elastomer. The lens arrays of different initial focal lengths and apertures can be fabricated by using the droplets of different volumes. Due to good elastic behavior of PDMS, the droplet lenses can be flexibly deformed, and the focal length and numerical aperture can be tuned by applying an external force on the PDMS elastomer. Furthermore, an apparatus for focal length tuning is designed and employed in the imaging system.

In order to fabricate a large-aperture continuous phase plate (CPP) using atmospheric pressure plasma processing (APPP) with high efficiency and precision, the position dwell mode and velocity mode were proposed and the iterative calculation method was developed for the non-constant removal rate. Two 320 mm × 320 mm × 2 mm CPPs were fabricated with two processing modes. The experiment results show that the velocity mode is capable of significantly reducing the processing time and shape error. The total processing time is decreased from 13.2 h to 9.3 h, and the surface shape error is decreased from 0.158λ to 0.119λ (λ = 632.8 nm) (root mean square).

In this Letter, we present a novel design method of image-side telecentric freeform imaging systems. The freeform surfaces in the system can be generated using a point-by-point design approach starting from an initial system consisting of simple planes. The proposed method considers both the desired object–image relationships and the telecentricity at the image-side during the design process. The system generated by this method can be taken as a good starting point for further optimization. To demonstrate the benefit and feasibility of our method, we design two freeform off-axis three-mirror image-side telecentric imaging systems in the visible band. The systems operate at F/1.9 with a 30 mm entrance pupil diameter and 5° diagonal field-of-view. The modulation-transfer-function curves are above 0.69 at 100 lps/mm.

A versatile nanosphere composite lithography (NSCL) combining both the advantages of multiple-exposure nanosphere lens lithography (MENSLL) and nanosphere template lithography (NSTL) is demonstrated. By well controlling the development, washing and the drying processes, the nanosphere monolayer can be well retained on the substrate after developing and washing. Thus the NSTL can be performed based on MENSLL to fabricate nanoring, nanocrescent and hierarchical multiple structures. The pattern size and the shape can be systemically tuned by shrinking nanospheres by using dry etching and adjusting the tilted angle. It is a natural nanopattern alignment process and possesses a great potential in the scope of nano-science due to its low cost, simplicity, and versatility for variuos nano-fabrications.

This Letter reports the formation of periodic surface structures on Ni–Fe film irradiated by a single femtosecond laser pulse. A concave lens with a focus length of 150 mm is placed in front of an objective (100×, NA=0.9), which transforms the Gaussian laser field into a ring distribution by the Fresnel diffraction. Periodic ripples form on the ablation area after the irradiation of a single femtosecond laser pulse, which depends on the laser polarization and laser fluence. We propose that the ring structure of the laser field leads to a similar transient distribution of the permittivity on the sample surface, which further launches the surface plasmon polaritons. The interaction of the incident laser with surface plasmon polaritons dominates the formation of periodic surface structures.

We present a new compact radar system to measure a terahertz radar cross section (RCS) of metal plates, trihedral corner reflectors, and an aircraft scaled model with a 0.1 THz continuous wave. We both numerically and experimentally investigate the terahertz RCS of the metal plates and trihedral corner reflectors. The numerical simulations are obtained by using commercial software, i.e., computer simulation technology, which agree well with the experimental results. Then, the RCS of an aircraft scaled model is measured, and the experimental results are in good agreement with the physical characteristics of the scaled model. The effectiveness of our compact radar system is verified to get the RCS of complex targets, such as the scaled models of the tactical targets.

A method of multi-beam femtosecond laser irradiation combined with modified HF-HNO3-CH3COOH etching is used for the parallel fabrication of all-silicon plano-concave microlens arrays (MLAs). The laser beam is split by a diffractive optical element and focused by a lens to drill microholes parallely on silicon. An HF-HNO3-H2SO4-CH3COOH solution is used to expand and polish laser-ablated microholes to form microlenses. Compared with the HF-HNO3-CH3COOH solution, the solution with H2SO4 can effectively reduce the etched surface roughness. The morphologies of MLAs at different laser powers and pulse numbers are observed. The image array formed by the silicon microlenses is also demonstrated.

This Letter presents an optical design method based on the Seidel aberration theory for dynamic refocus systems. The function of a dynamic refocus system is to increase the amount of return photons when a pulsed laser travels over an extended height range. In this study, the dynamic refocus system is a short focal image system. The aberrations of the dynamic refocus system are calculated individually. Aplanatic lenses are used to eliminate the main spherical aberration. A field lens is used to change the stop position in order to eliminate comas and astigmatism. The effectiveness of the initial design results are confirmed, and the designed dynamic refocus objective with an aperture of F-number 0.98 and a focal length of 14.325 mm is achieved. The total motion of the dynamic refocus mirror is approximately 216 μm at heights that ranged from 8 to 18 km. The optimum result shows that the dynamic refocus system is an ideal optical image system at each conjugating height with 10 km sample thicknesses.

The aim of this work is to provide an analytical method based on experimental measurements in order to obtain the prismatic film deformation for different curvatures of hollow cylindrical prismatic light guides (CPLGs). To conform to cylindrical guides it is necessary to bend the film to guide the light; changes induced by curving the film give rise to deformation shifts. Light losses affected by deformation are experimentally evaluated and numerically analyzed. The effect of deformation on prism angle is especially increased for CPLGs of curvatures higher than 20 m 1. An experimental method for the accurate transmittance of measurements related to bending is presented.

The efficiency balance phenomenon for see-through head-mounted displays with different microstructure conditions can be found both theoretically and using optical simulation software. A simple mathematical calculation is used to determine the relationship between the real image (see-through function) energy and the virtual image energy. The simulation is based on factors taken from previous research studies. It is found that the balance value of the optical efficiency remains almost constant (66.63% to 67.38%) under different microstructure conditions. In addition, suitable conditions for the microstructures in see-through head-mounted displays for daily applications can be predicted.

Off-axis systems built by freeform optics are greatly demanded in next-generation space telescopes/cameras, for obtaining a long focal length and wide field of view. The profile accuracy of the mirror surface is the most critical parameter, which is finally required about 12 nm in peak-to-valley. Therefore, technologies for accurately and efficiently machining and testing freeform surfaces are greatly demanded. In this work, an ultrasonic-vibration-assisted five-axis grinding technology is developed and verified by grinding silicon carbide mirror blanks on a machine center having common precision. Subsequently, a computer-controlled optical surfacing technology is developed for lapping and polishing the mirror. A computer-generated hologram is developed for testing the mirror surface. This work provides an efficient resolution for the fabrication and measurement of freeform surfaces.

In this Letter, we present a method to measure the eccentricity of an off-axis asphere using a laser tracker during optical null testing. We first adjust the optical path of the null testing, and then probe some necessary reference surface on the compensator or the off-axis mirror’s body with a laser tracker. Next, using the collected data to process, construct, build the coordinate system, solve, and so on, we obtain the eccentricity directly through comparing the central point of the asphere and the tested optical axis. A measurement experiment is conducted with a circular off-axis aspherical mirror; the result shows that the measurement accuracy can reach 0.1859 mm, 6.2% of its tolerance belt.

We use inductively coupled plasma chemical etching technology (PCET) operating at atmospheric pressure to fabricate an optical mirror whose materials are fused silica, reaction bonded SiC, sintered SiC, and Si for the first time, to our best knowledge. This Letter is focused on a primary study of the mirror surface roughness fabricated with a plasma torch on different wafers. The four wafers’ surface roughness after PCET fabrication are Ra 0.053, 0.223, 0.612, and 0.027 μm, respectively (increased 5, 40, 1.07, and 2 times, respectively). The micro-transformation principle of the surface roughness is researched with an Olympus LEXT 450. We analyze the main reasons that underpin the surface roughness increase. The experimental results show that the new technology is valid for fabricating Si-based materials. Consequently, inductively coupled PCET operating at atmospheric pressure shows promise for the future.

A new method developed for wavefront error (WFE) testing of an assembled space telescope is described in this Letter. The main idea of this method is to image a small bright target on the focal plane array assembly by the space telescope itself; the imaging light beams can be reflected to the focal plane array by a plane mirror in front of the aperture of the system under test and two images (one is in-focus and the other is defocused) can be obtained. The WFE of the optical system can be calculated with a phase diversity algorithm according to two images of the target on the focal plane array assembly. The residual error and limitations of this method are discussed and a simulation result is shown, which shows the application potential of this technology.

This Letter reports a series of experiments on examining the removal function of a 400 mm magnetorheological finishing (MRF) polishing wheel which is aimed at large optical component fabrication. This MRF equipment is assembled on the large computer numerical control center whose effective axial length is 3000 mm. The two different removal functions of the wheel are used to virtually fabricate a 1450 mm concave fused silica aspherical optical mirror. The total fabrication times are 110 and 309 h, respectively. The final surface errors are eventually reduced to 0.014λ and 0.024λ after the process, and the convergence rates are 97.46% and 95.65% in one virtual fabrication cycle. The power spectrum density is used to analyze the spacial frequency based on the final simulating surface error, and the middle and low spacial frequency surface error controlling ability is analyzed in terms of different removal functions.

The slope of the root-mean square (RMS) can be applied to evaluate mid-spatial frequency mirror surface errors for larger-aperture mirrors. In this paper, the slope RMS is analyzed from three different perspectives. First, the relationship between the slope RMS and the basis polynomials is discussed, and the mathematical relationship between the slope RMS and the standard orthogonal basis is obtained. Second, the slope RMS is analyzed by applying the Wiener process, with the results indicating that the ideal mirror surface error obeys the Gauss distribution law. Then, a power spectrum analysis method based on the slope RMS is proposed. Finally, the method is used to analyze the Thirty Meter Telescope tertiary mirror surface figure.

The theoretical study of the film thickness distribution deposited on a parabolic substrate by vacuum evaporation is reported. It is derived that the value of n/h and L/h strongly affect the coating thickness distribution (where h is the height of the substrate and n and L are, respectively, the horizontal distance and vertical height between the evaporation source and the center of the parabolic bottom). All of the parabolic substrate can be coated when n≤ph(1+L/h) (where the parabolic focal length is p/4), otherwise there is “blind area” on the substrate. In addition, the excellent thickness uniformity of the coating on the whole parabolic substrate can be obtained by choosing the appropriate configuration of the evaporation system under different evaporation sources.

We study a convex off-axis aspheric mirror which works as secondary mirror in space optical system. The parameters of the mirror are described. In order to test the surface error, the mirror is made up of fused silicon and is tested by the backside transmission type. The shape accuracy while grinding is controlled using coordinate measuring machining testing. The distortion of the measurement is corrected by affine transformation. The ion beam figuring is used for surface finishing and to achieve root mean square of 0.015λ (λ = 632.8 nm).

Silicon carbide (SiC) is a wide bandgap semiconductor which exhibits outstanding mechanical, chemical properties, and potential for a wide range of applications. Laser technology is being established as an -indispensable powerful tool to induce structural or morphological modifications on hard brittle materials. SiC (6H-SiC wafer) is irradiated by nanosecond pulsed Nd:YAG laser to evaluate microstructure and mechanical properties of irradiation areas. Raman spectroscopy analysis reveals that irradiations produce homonuclear Si-Si bonds and disordered phase of crystalline SiC. Crystal structure changes are observed as a consequence of laser-induced melting and resolidification. Hardness in the irradiation area exhibits a significant decrease. The formation of silicon film facilitates material removal rate, surface electrical conductivity, and ceramics conjunction.

In order to obtain precise optical free-form convex mirror, we present a perfect process specification for fabricating and testing optical free-form convex mirror. Some technical requirements of 84×84 (mm) optical free-form convex silicon carbide (SiC) mirror are introduced. Firstly, the SiC blank is milled to the best-fitting sphere by means of DMG Ultrasonic 100-5 computer-controlled machine. Secondly, the best-fitting sphere is grinded and polished to optical free-form surface with certain figure accuracy by computer-controlled small tool fabrication. Finally, in order to meet the requirement of design, the optical free-form convex mirror is fabricated by advanced ion beam figuring. The contour testing technique is used for measuring the optical free-form convex mirror in milling and grinding processes, and the computer-generated hologram null testing technique for measuring the optical free-form convex mirror in polishing process is studied. The final testing result indicates that the figure accuracy of the optical free-form convex mirror is 0.02. (root mean square).

Aspheric elements are widely applied in optical systems and the vertex radius of curvature (VROC) is one of the important fundamental parameters of an asphere. We present a method for measuring the VROC of asphere. We use a portable laser tracker to measure the optical interval of the null testing path and then determine the VROC of the asphere through ray tracing. Based on this method, we carry out an accurate measurement. The accuracy can reach up to 0.056 mm on an asphere with VROC of approximately 2 m and the relative error is 0.003%.

Hollow, cylindrical, prismatic light guides (CPLGs) are optical components that, using total internal reflection (TIR), are able to transmit high-diameter light beams in daylight and artificial lighting applications without relevant losses. It is necessary to study the prism defects of their surfaces to quantify the behavior of these optical components. In this Letter, we analyze a CPLG made of a transparent dielectric material. Scanning electron microscopy (SEM) and the topographic optical profilometry by absorption in fluids (TOPAF) imaging technique are conducted to determine if there are defects in the corners of the prisms. A model for light guide transmittance that is dependent on prism defects is proposed. Finally, a simulation and an experimental study are carried out to check the validity of the proposed model.

A simple method to fabricate vertically coupled micro-ring resonators in amorphous silicon-on-insulator is created by a three-step lithography process. First, the linear loss at 1.55 μm of the a-Si:H film is calculated to be 0.2±0.05 dB/cm. Then, the bottom line waveguide of Su-8 with a flat top surface of 300 nm is created by etching. The thickness of Su-8 can easily be controlled by the etching time. Finally, by opening the window pattern and etching several layers, the first layer marks made by electron beam lithography are found with a 50 nm resolution, and the high quality of the micro-ring resonator is demonstrated.

An interesting transition between low spatial frequency laser-induced periodic surface structure (LIPSS) and high spatial frequency LIPSS (HSFL) on the surface of nickel is revealed by changing the scanning speed and the laser fluence. The experimental results show the proportion of HSFL area in the overall LIPSS (i.e., K) presents a quasi-parabola function trend with the polarization orientation under a femtosecond (fs) laser single-pulse train. Moreover, an obvious fluctuation dependence of K on the pulse delay is observed under a fs laser dual-pulse train. The peak value of the fluctuation is found to be determined by the polarization orientation of the dual-pulse train.

Adaptive optics (AO) systems greatly improve the resolution of retinal imaging instruments by actively correcting ocular aberrations. In this Letter, closed-loop correction as well as ocular aberration compensation of a 62-element silicon unimorph deformable mirror (DM) driven by only positive voltage is performed. The experimental results show that the root-mean square (RMS) wavefront of the initial mirror surface is reduced to 0.011 μm in a closed-loop AO system. The DM reproduces Zernike shapes from the third to 35th mode accurately. The simulated compensation of 200 ocular wavefronts shows that the average RMS value after correction is reduced to 0.017 μm.

A real-time monitoring system is set up based on a computer, dynamic interferometer, beam expanding system, and a beam reflecting system. The stability and repeatability of the monitoring system is verified. A workpiece and a glass monitoring plate are placed in the same ring. The surface figure of the workpiece, monitored by the monitoring plate, synchronizes with the surface of the glass monitoring plate in terms of peak–valley and power. The influence of the reflection and transmission surface are discussed in theory and a numeral deviation in online and offline testing data is quantitatively analyzed. The new method provides a quick and easy real-time method to characterize changes to the optical surface during polishing.

We design a plano-convex lens working in the terahertz (THz) frequency range and fabricate it using three-dimensional (3D) printing technology. A 3D field scanner is used to measure its focal properties, and the results agree well with the numerical simulations. The refractive index and absorption coefficient measurements via THz time-domain spectroscopy (THz-TDS) reveal that the lens material is highly transparent at THz frequencies. It is expected that this inexpensive and rapid 3D printing technology holds promise for making various THz optical elements.

Silicon (Si) modification layer on silicon carbide (SiC) surface is widely used in space optical systems. To achieve high-quality optical surface, the technology of ion beam figuring (IBF) is studied. The radio frequency ion beam source is introduced briefly. Then the removal function experiment is studied. The volume removal stability of the IBF reached 97% in 10 h continuous working testing. The parameters of the IBF removal function are calculated by Gaussian fitting including the removal rate and the full-width half-maximum. Then the removal function results are used in practical fabrication. The workpiece is a plane with Si modification layer on SiC surface. After 148 min processing IBF, the final surface error reaches 1.2 nm RMS.

We present the mechanism of coherent population trapping (CPT) atom clock. The optical system is designed for a portable CPT atom clock. In this system, single transverse mode vertical-cavity surface-emitting laser is used as a miniature pump laser. The driven circuit is designed based on a field-programmable gate array full digital control system and special-purpose chip MAX1968. The experimental results show that the optical system can provide circularly polarized light, and has small volume and low power consumption. These indi-cate that the optical system is a promising candidate for a portable CPT atom clock engineering prototype.

Off-axis aspherical mirrors are growing in popularity in modern space-borne cameras having high resolutionand large field of view. Fabrication processes for these mirrors include surface generation by grinding wheel, free-abrasive lapping, and various polishing cycles. Surface generation by grinding wheel is the most efficient process among the whole fabrication processes. Therefore, technologies for accurately and cost efficiently generating the mirror blanks are highly indispensable. We propose, a single-point grinding mode and a four-step tool path generation technology to resolve the over travel problem, for directly machining the off-axis aspherical mirror blank. Technologies for surface geometrical modeling and wheel wear reduction/compensationare established. Using a commercial-available HASS-VF8 machining center, a silicon carbide mirror blank having a 1.45 m aperture is successfully generated. Result indicates that the main error source affecting the obtained grinding accuracy is wheel wear amount, other than the positioning accuracy of machining center. Therefore, error-compensation grinding is indispensable. We provide an alternative economical resolution to efficiently fabricate the large-scale off-axis aspherical surface.

In order to obtain high-quality flat mirror, a serial mode combined polishing technology, consisting of continuous polishing (CP) and ion beam figuring (IBF), is presented. The function of CP technology is to get certain figure accuracy and meet the requirements of the surface roughness of the flat mirror. The final high figure accuracy of the flat mirror is achieved by the IBF technology. We introduce the polishing principles of CP and IBF and then, the polishing experiment and material removal function of IBF are studied. Finally, a F 160 mm flat mirror is polished by a serial mode combined polishing technology. After serial mode com-bined polishing, the surface error and roughness of the flat mirror are 2.06 and 0.42 nm RMS, respectively. The experiment results indicate that the serial mode combined polishing technology is effective for polishing ultra-precise flat mirror.

Swing arm profilometer is a useful metrology tool for large optics. For larger mirrors, the testing accuracy decreases as the arm becomes longer, while the testing accuracy requirement remains the same. We introduce a simple solution to make testing of large mirrors with shorter arms possible, which improves the testing accuracy, especially reduces the uncertainty of low-order shapes like astigmatism and trefoil. Simulation and experiment results show that testing uncertainty of low-order shape and high-frequency errors reaches 0.1 \mu m RMS, which faithfully meets the requirement of profile testing to guide the grinding and coarse polishing process.

As aerospace technology develops rapidly, higher demand for aerospace optic system is brought forward. With its excellent physical qualities, SiC becomes a very promising material for speculums. The material-remove mechanism of SiC surface polishing is studied, that is, the grinding mechanism of ceramic material. Indentation fracture model is also introduced and is used to explain material-remove mechanism of SiC surface polishing, and the model of SiC polishing in ideal condition is analyzed. Finally, the material-remove mechanism of SiC polishing in real state is studied.

The removal function test is carried out on the earlier round-pellet polishing pad. The concept of filling factor is introduced to evaluate the removal function obtained from the experiments mentioned in the paper. To improve the filling factor and characteristics of the polishing pad, the pad structure is optimized according to the experimental results of the round-pellet pad. The removal function of the new polishing pad is simulated with MATLAB. The stability experiment is carried out in full aperture at the same time. The fixed abrasive and the slurry abrasive polishing experiment both are performed under the same conditions. Finally, the structural similarity index is introduced to evaluate the similarity between simulations and experiments. The best structural similarity index of multi-square-pellet pad is 0.4257. The comparison results are acceptable and positive. The optimized fixed abrasive polishing pad is proved to be highly promising for large-diameter SiC mirror fabrication.

Demand for large-scale off-axis aspherical mirrors is increasing in next-generation space-borne optical imaging systems. In this paper, a variable-axis single-point grinding strategy is developed for precisely, cost-effectively figuring silicon carbide (SiC) mirror blanks that have high-order high-gradient off-axis aspherical surfaces on a precision five-axis machining center. The grinding strategies also include tool path generation/optimization, feeding direction control and wheel wear reduction/compensation. Applying the developed grinding strategies, by only one grinding cycle, a near-circular Φ372-mm SiC mirror blank is successfully grounded to 7.8 μm in peak to valley, which is comparable to the reported machining accuracy of the BoX? ultraprecision grinding machine. Moreover, the wheel need not have to be dressed during the whole grinding cycle due to the rotary ultrasonic grinding method. Therefore, this paper offers an efficient and economic solution for grinding off-axis aspherical and free from sur to micron-level accuracy, thus significantly decreasing the subsequent lapping/polishing production cycle time.

Wavefront coding (WFC) is kind of computational imaging technique that controls misfocus and misfocus-related aberrations of optical systems by appending a specially designed phase distribution to the pupil function. This technology has been applied in many fields to increase the performance or/and reduce the cost of imaging systems. The application of WFC technology on an off-axis three-mirror anastigmatic (TMA) system has been proposed in our previous work. In this letter, we describe the alignment, the imaging experiment and image restoration of an actual TMA system with WFC technology.

In conventional pulsed laser deposition (PLD) technique, plume deflection and composition distribution change with the laser incident direction and pulse energy, then causing uneven film thickness and composition distribution for a multicomponent film and eventually leading to low device quality and low rate of final products. We present a novel method based on PLD for depositing large CIGS films with uniform thickness and stoichiometry. By oscillating a mirror placed coaxially with the incident laser beam, the laser's focus is scanned across the rotating target surface. This arrangement maintains a constant reflectance and optical distance, ensuring that a consistent energy density is delivered to the target surface by each laser pulse. Scanning the laser spot across the target suppresses the formation of micro-columns, and thus the plume deflection effect that reduces film uniformity in conventional PLD technique is eliminated. This coaxial scanning PLD method is used to deposit a CIGS film, 500 nm thick, with thickness uniformity exceeding ±3% within a 5 cm diameter, and exhibiting a highly homogeneous elemental distribution.

This letter presents a model of an indoor light positioning system (LPS) based on white LEDs and a camera. The position of an LPS receiver is determined through both its relative position to LEDs according to their images captured by the camera and LEDs' absolute position information in the navigation frame, obtained through a visible light communication (VLC) link. The error performance of the proposed LPS is analyzed. The mean error and mean square error (MSE) of estimated receiver position using least squares (LS) and weighted least squares (WLS) estimators are both derived in the presence of non-uniform measurement bias and white Gaussian noise. The effects of communication data rate on the positioning accuracy are also studied through BER performance.

Presently, energy conservation and carbon dioxide emission reduction have become increasingly important because of global warming. Using solar energy, which is considered as one of the most important renewable energy sources, does not only decrease the consumption of fossil fuels, but also slows down the pace of global warming. For indoor illumination, our team has developed a technique called "Natural Light Illumination." Instead of using solar cells, our system directly guides sunlight into the interior of a structure. However, the efficiency of the light-collecting module is still low. To address this problem, we propose a new light-collecting module based on a prism array structure with high efficiency. We use optical simulation tools to design and simulate the efficiency of the module, which is found to be 57%. This value is higher than that of the original concentrator (i.e., 11%).

Toroidal surface and biconic surface are employed increasingly, however their profile cannot be null tested easily for they are non-rotationally symmetrical. Null testing method with cylinder compensator is proposed to solve this problem. The theory of this method is revealed. The errors of this method are present. Three typical testing optical systems with cylinder compensator are demonstrated at last. The design results and total error indicate that this method is feasible.

The thin mirrors are widely used in active optical system. In this letter, magnetic medium assistant polishing (MMAP) technology and device are discussed for thin mirrors optical finishing. The principle of MMAP is introduced, the magnetic tool for polishing is designed, and the removal function of magnetic polishing tool is studied. On the basis study of the material removal function especially removal property in the edge region, the tool-path is optimized, and the dwell time distribution of computer-controlled MMAP is researched. The glass thin mirror is polished by MMAP technology. The diameter of the work-piece equals S22201 150 mm and the thickness is 5 mm. The initial surface error is 0.19\lambda (root mean square (RMS)) , and after two steps fabrication, the final surface error reaches 0.02\lambda. The experimental rsults verify that the technology is effective for thin mirrors finishing.

A new sub-aperture overlapping area fusion algorithm based on wavelet transformation is proposed to retain high-frequency components as much as the measurements in the sub-aperture overlapping areas. The principles of sub-aperture stitching are briefly introduced, and the fusion algorithm based on wavelet transformation is demonstrated. The results of the experiment indicate that the new algorithm improves the retention of high-frequency measurement components.

We report the direct fabrication of a microfluidic chip composed of two high-aspect ratio microfluidic channels with lengths of 3.5 cm and 8 mm in a glass substrate by femtosecond laser micromachining. The fabrication mainly consists of two steps: 1) writing microchannels and microchambers in a porous glass by scanning a tightly focused laser beam; 2) high-temperature annealing of the glass sample to collapse all the nanopores in the glass. Migration of derivatized amino acids is observed in the microfluidic channel by applying electric voltage across the long-migration microchannel.

A new type of silica optical micro-kayak cavity fabricated on a silicon chip is designed and demonstrated. This micro-kayak cavity with two straight sides and two semi-circle sides can be used to achieve a compact and flexible arrangement in the design of integrated photonic circuits. The micro-kayak cavity can also be embedded with a Bragg reflection grating in the straight sides for frequency selection using a micro-kayak cavity laser doped with a rare-earth ion. We describe the fabrication methods for the micro-kayak cavity, obtain its spectra, and discuss its potential applications.

Freeform optical surfaces (FOSs) will be the best elements in the design of compact optical systems in the future. However, it is extremely difficult to measure freeform surface with sufficient accuracy, which impedes the development of the freeform surface. The design and fabrication of computer-generated hologram (CGH), which has been successfully applied to the tests for aspheric surfaces, cannot be directly adopted to test FOSs due to their non-rotational asymmetry. A novel ray tracing planning method combined with successively optimizing even and odd power coefficients of phase polynomials in turn is proposed, which can successfully design a non-rotational asymmetry CGH for the tests of FOSs with an F-\theta lens. A new eight-step fabrication process is also presented aiming to solve the problem that the linewidth on the same circle of the CGH for testing freeform surface is not uniform. This problem cannot be solved in the original procedure of CGH fabrication. The test results of the step profiler show that the CGH fabricated in the new procedure meets the requirements.

We present linear conjugated combined aberration modes with a concentric pupil diameter of 4 mm. The combinations are according to the coupling relationship between Zernike modes over the concentric circle domain within the unit circle and the root mean square decreasing amplitude ratio of the corresponding aberration modes in the concentric pupil, in which the reconstruction pupil diameter is 6 mm. Each combined mode shares the characters of 2 radial orders apart, the same azimuth frequency, the same coefficient sign, and the prescribed amount, such as (C02 = 0.7\lambda, C04 = 0.3\lambda), (C-33 = 0.8\lambda, C-35 = 0.3\lambda), and so on. We also analyze the influence of the combined modes on optical quality. Simulations and experiments show improvement after combination; they also indicate that the influence of conjugated combination on optical quality has compensation and not superposition.

Natural light illumination system (NLIS) generates increasing research interest because of the recent trend toward green energy. Various crucial optical components used in a NLIS are analyzed, designed, and fabricated to obtain high efficiency. A large amount of light is loss because of the large viewing angle during light transmission. A tapered light pipe (TLP) is used to collimate light viewing angles. In this letter, we combine a TLP and a traditional lens as a new coupler based on Etendue theory. The original efficiency is only 17.54%, but the efficiency reaches more than 70% when the new coupler is applied.

Visible light communication between light emitting diode (LED) traffic lights and vehicles with a receiving photodiode front-end is developed for intelligent transportation systems. In this letter, the communication data rates for different ranges are evaluated. The data rates are based on real scenarios of the background noise and path losses and are experimentally obtained with a testing system built upon commercial off-the-shelf components. Comparisons of range-rate performance for different average noise levels are also conducted with the use of red/yellow/green LED lights. Results show that achieving the data rates of kilobits per second at a communication range of hundred meters is possible under the ordinary noise scenario, a finding that is highly significant for practical applications.

The issue of the letter is focused on the RB-SiC aspherical mirror high frequency surface quality which is fabricated with the different type fixed abrasive pellets. The two-dimensional (2D) surface roughness of the mirror is simulated and experimented. The errors between the simulation and the experiment are 5.97%, 3.19%, 3.59%, 37.37% using W1.5, W3.5, W5, W7 pellets respectively. The error emerging reason is analyzed in detail after the comparison. Also the fractal theory is applied on the analysis of the optical mirror surface fabricated with the fixed abrasive technology. The analysis result shows that the good surface quality of the RB-SiC mirror can be obtained quickly with being polished with the fixed abrasive technology. So the fixed abrasive technology is very suitable for the fast optical surfacing, especially can obtain good surface roughness fast in the stage of grinding mirror which is not suitable for being tested with interferometer.

The optimized oxygen inductively coupled plasma etching parameters are systematically studied to fabricate Poly (methyl-methacrylate-glycidly-methacrylate) inverse ridge waveguide with smooth vertical features. The etch rate, surface roughness and vertical profile are characterized by atomic force microscopy and scanning electron microscopy. The optimized etching parameters are found to be 400-W antenna-RF power, 30-W radio frequency (RF) bias power, 1-Pa-chamber pressure, and 40-sccm be O2-flow rate. Spincoating butyl acetate diluted polymer solution onto the channel waveguide is proved to be an effective method which can decrease the surface roughness. According the results, the RMS rouqhness of the film decreases 80%. Optical propagation loss can be reduced from 2.6 to 1.5 dB/cm for the above reason.

A fixed abrasive technology combined with computer controlled optical surfacing is discussed, and a removal function model for multi-pellet polishing pad is established based on the removal function theory of planar motion. The parameters of the model, such as the movement eccentricity of the polishing pad and the distance between pellets, are optimized by introducing a approaching factor and a curve RMS distance in the simulation. The comparison of the theoretical model and the experimental results indicate that the error between the theoretical maximum removal rate and the experimental data is 0.0073 \mu m/min, and its error ratio is 5.58%; the RMS distance error between the theoretical removal function curve and the experimental curve is 0.0849 μm and its error ratio is 7.01%. The veracity of the theoretical model is verified by experimental results, which predicts the feasibility of the fixed abrasive polishing technology and establishes a promising basis for the SiC mirror precision fabrication field.

Annular field aberrations of a three-reflection concentric system, which are composed of two spherical mirrors, are analyzed. An annular field with a high level of aberration correction exists near the position where the principal ray is perpendicular to the object-image plane. Aberrations are determined by the object height and aperture angle. In this letter, the general expression of the system aberration is derived using the geometric method, and the non-approximate design method is proposed to calculate the radii of the annular fields that have minimum aberrations under different aperture angles. The closer to 0.5 (the ratio of the radius of convex mirror to the radius of concave mirror) is, the smaller the system aberration is. The examples analyzed by LABVIEW indicate that the annular field designed by the proposed method has the smallest aberration in a given system.

We present an optical design for a fingerprint scanner that addresses the challenges involved in capturing the prints of rolling fingers. A rolling fingerprint scanner requires a high performance distortion free system with big object space numerical aperture (0.022) and larger capture size (40 \times 40 (mm)). We show how these requirements can be achieved with the approach of optical and computational hybrid distortion correction. In addition, dark background illumination is utilized to increase fingerprint contrast.

Fabrication details of air-bridged Kerr nonlinear polymer photonic crystal slab structures are presented. Both the two-dimensional photonic crystal slab and the one-dimensional nanobeam structures are fabricated using direct focused ion beam etching and subsequent wet chemical etching. The scanning electron microscopy images show the uniformity and homogeneity of the cylindrical air holes. The optical measurement in the near-infrared region is implemented using the tapered fiber coupling method, and the results agree with the numerical calculations by using the three-dimensional finite-difference time-domain method.

A parametric optimization method is proposed in the design of a high-efficiency free-form illumination system. The proposed method is intended to provide rectangular uniform illumination with a light emitting diode (LED) source. An initial illumination system is first constructed and parameterized. The parameters of the initial system are optimized according to actual simulation results, and one design sample is presented. A liquid crystal on silicon (LCoS) micro-projector test module is fabricated and tested based on the design sample. Compared with the conventional micro-projectors using rotational symmetry devices, the micro-projector system designed with the parametric optimization method can send 1.65 times the source power to the LCoS active area with a 4:3 target ratio, and the uniformity reaches 98%.

A new removal optimization method called submerged jet polishing (SJP) is reported. Experiments are conducted to obtain the removal shape. Results of SJP indicate that a Gaussian shape removal function can be obtained and that the removal rate is sensitive to variations in the standoff distance. SJP is applied to the corrective figuring of a BK7 optical glass. The flatness is improved from photovolatic (PV) 0.066 \lambda to 0.024 \lambda (\lambda=632.8 nm) after three iterations, and the root mean square (RMS) value is improved from 0.013 \lambda to 0.00395 \lambda. The experimental result indicates that SJP has a capability for ultra-precision figuring and can be applied in polishing complex-shaped surfaces.

Wolter I collector is the best collector for extreme ultraviolet (EUV) lithography, which has a series of nested mirrors. It has high collection efficiency and can obtain more uniform intensity distribution at the intermediate focus (IF). A new design with the calculation sequence from the outer mirror to the inner one on the premise of satisfying the requirements of the collector is introduced. Based on this concept, a computer program is established and the optical parameters of the collector using the program is calculated. The design results indicate that the collector satisfies all the requirements.

We investigate the aberration properties of the conformal optical system with decentered and tilted elements by vector aberration theory. By decentering and tilting the window and corrector of the system, two elements are effectively used together in a particular manner by aberration compensation to achieve off-axis imaging. A conceptual design is performed with a half-field of 2?, the F# of 4, and the wavelength ranging of 3700~4800 nm. The imaging quality can reach the optical diffraction limit and satisfy corresponding requirements.

A new process of magnetorheological figuring (MRF) based on the deliquescence theory is proposed to finish KDP crystals. A novel, non-aqueous, and abrasive-free magnetorheological (MR) fluid is explored, and polishing experiments are performed on a self-developed MRF machine. The removal mechanism is reckoned to be the result of a combination of dominant chemical etching and accessorial mechanical drag. The results indicate that the surface roughness of I plate KDP of 80×80 (mm) polished by MRF is 1.2 nm (root mean square (RMS)), and the tool marks are completely removed. The surface accuracy by MRF is 0.035\lambda (RMS), and the low/middle-frequency errors are significantly corrected after MRF.

Shrinking of critical dimensions (CDs) in semiconductor circuits has been pushing optical lithography to print features smaller than the wavelength of light source. The demand for CD control is ever-increasing. In this paper, the study is conducted to reveal the impact of illumination pupil filling ellipticity on CD uniformity. As main parameters of CD uniformity, horizontal-vertical feature bias (H-V bias) and isolated-dense feature bias (I-D bias) caused by pupil filling ellipticity are calculated using the PROLITH software under four different illumination settings. Simulation shows that H-V bias and I-D bias are proportional to the pupil filling ellipticity. The slopes of the fitting lines of the H-V bias versus pupil filling ellipticity are calculated.

For the dual-galvanometric laser scanning manufacturing, the traditional geometry algorithm-fθ only considered the distance between the two swaying mirrors, the distance between the swaying mirror and the convex lens, the mirror swaying angle, and the lens focal length. And it could not correctly express the manufacturing track which was made geometry distorted. Based on analysis, a creative geometry control algorithm --- optical entire factors (OEF) was brought forward. From the creative algorithm it can be known that OEF geometry control algorithm was concerned with not only the distance of the two swaying mirrors, distance between the swaying mirror and the convex lens, mirror swaying angle, and lens focal length, but also the lens central height, lens convex radius, and medium refractive index. The manufacturing system can manufacture satisfied geometry with the creative double ends approach (DEA) control model based on OEF in the experiments.

The ABCD law of parameter q for fundamental-mode Gaussian beam is deduced in this paper. The result shows that the changes of focal length and focal depth are not related to the orders of the Gaussian beam modes when focus lens moves along optical axis in a large range, indicating that the ABCD law of parameter q can be used for any order modes. A laser focusing setup is designed, and the response characteristics of oil pressure system therein are also studied.