Fluorescence microscopy technology uses fluorescent dyes to provide highly specific visualization of cell components, which plays an important role in understanding the subcellular structure. However, fluorescence microscopy has some limitations such as the risk of non-specific cross labeling in multi-labeled fluorescent staining and limited number of fluorescence labels due to spectral overlap. This paper proposes a deep learning-based fluorescence to fluorescence (Fluo-Fluo) translation method, which uses a conditional generative adversarial network to predict a fluorescence image from another fluorescence image and further realizes the multi-label fluorescent staining. The cell types used include human motor neurons, human breast cancer cells, rat cortical neurons, and rat cardiomyocytes. The effectiveness of the method is verified by successfully generating virtual fluorescence images highly similar to the true fluorescence images. This study shows that a deep neural network can implement Fluo-Fluo translation and describe the localization relationship between subcellular structures labeled with different fluorescent markers. The proposed Fluo-Fluo method can avoid non-specific cross labeling in multi-label fluorescence staining and is free from spectral overlaps. In theory, an unlimited number of fluorescence images can be predicted from a single fluorescence image to characterize cells.

Atherosclerotic cardio-cerebral vascular disease is the most common disease that threatens human health. Many researches indicated that oxidatively modified low-density lipoprotein (ox-LDL) is a key pathogenic factor of atherosclerosis. Here, we report the change of the secondary structure of ox-LDL caused by photoirradiation in an optofluidic resonator. The content ratios of amphipathic α-helices and β-sheets of ox-LDL are changed under laser beam illumination, resulting in an increasing binding rate of ox-LDL and ox-LDL antibodies. Our findings may provide a potential way for clinical atherosclerosis treatment and prompt recovery rate of atherosclerotic cardio-cerebral vascular disease by optical technology and immunotherapy.

Printing stable color with a lithography-free and environment-friendly technique is in high demand for applications. We report a facile strategy of ultrafast laser direct writing (ULDW) to produce large-scale embedded structural colors inside transparent solids. The diffraction effect of gratings enables effective generation of structural colors across the entire visible spectrum. The structural colors inside the fused silica glass have been demonstrated to exhibit excellent thermal stability under high temperature up to 1200°C, which promises that the written information can be stable for long time even with unlimited lifetime at room temperature. The structural colors in the applications of coloring, anti-counterfeiting, and information storage are also demonstrated. Our studies indicate that the presented ULDW allows for fabricating large-scale and high thermal-stability structural colors with prospects of three-dimensional patterning, which will find various applications, especially under harsh conditions such as high temperature.

Broadband super-resolution imaging is important in the optical field. To achieve super-resolution imaging, various lenses from a superlens to a solid immersion lens have been designed and fabricated in recent years. However, the imaging is unsatisfactory due to low work efficiency and narrow band. In this work, we propose a solid immersion square Maxwell’s fish-eye lens, which realizes broadband (7–16 GHz) achromatic super-resolution imaging with full width at half-maximum around 0.2λ based on transformation optics at microwave frequencies. In addition, a super-resolution information transmission channel is also designed to realize long-distance multi-source super-resolution information transmission based on the super-resolution lens. With the development of 3D printing technology, the solid immersion Maxwell’s fish-eye lens is expected to be fabricated in the high-frequency band.

A sensor based on light-induced thermoelastic spectroscopy (LITES) with a fiber-coupled multipass cell was demonstrated for carbon monoxide (CO) detection. The fiber-coupled structure has the merits of reducing optical interference and difficulty in optical alignment and increasing system robustness. A 1.57 µm continuous wave distributed feedback diode laser was used as the excitation source. A minimum detection limit of 9 ppm was obtained, and the calculated normalized noise equivalent absorption coefficient was 1.15×10-7 cm-1·W·Hz-1/2. The reported CO-LITES sensor showed excellent linear concentration response and system stability.

We designed a tunable wavelength-selective quasi-resonant cavity enhanced photodetector (QRCE-PD) based on a high-contrast subwavelength grating (SWG). According to simulation results, its peak quantum efficiency is 93.2%, the 3 dB bandwidth is 33.5 GHz, the spectral linewidth is 0.12 nm, and the wavelength-tuning range is 28 nm (1536–1564 nm). The QRCE-PD contains a tunable Fabry–Perot (F-P) filtering cavity (FPC), a symmetrical SWG deflection reflector (SSWG-DR), and a built-in p-i-n photodiode. The FPC and the SSWG-DR form an equivalent multi-region F-P cavity together by multiple mutual mirroring, which makes the QRCE-PD a multi-region resonant cavity enhanced photodetector. But, QRCE-PD relies on the multiple-pass absorption enhanced effect to achieve high quantum efficiency, rather than the resonant cavity enhanced effect. This new photodetector structure is significant for the application in the dense wavelength division multiplexing systems.

The 4H-silicon carbide on insulator (4H-SiCOI) has recently emerged as an attractive material platform for integrated photonics due to its excellent quantum and nonlinear optical properties. Here, we experimentally realize one-dimensional photonic crystal nanobeam cavities on the ion-cutting 4H-SiCOI platform. The cavities exhibit quality factors up to 6.1×103 and mode volumes down to 0.63 × (λ/n)3 in the visible and near-infrared wavelength range. Moreover, by changing the excitation laser power, the fundamental transverse-electric mode can be dynamically tuned by 0.6 nm with a tuning rate of 33.5 pm/mW. The demonstrated devices offer the promise of an appealing microcavity system for interfacing the optically addressable spin defects in 4H-SiC.

A good thermo-optic property of strontium dodeca-aluminum oxide (SrAl12O12, SRA) host material is very advantageous to the development of high-performance lasers by doping rare-earth ions for gain medium. In this work, we report on diode-end-pumped high-performance continuous-wave and passively Q-switched Nd:SRA lasers. For continuous-wave operation, a maximum output power of 6.45 W is achieved at 1049 nm with a slope efficiency of about 41.6%. Using a Y3Al5O12 (YAG) etalon, we have firstly achieved a 1066 nm laser with a maximum output power of 4.15 W and a slope efficiency of about 27%, to the best of our knowledge. For passively Q-switched operation, with Cr4+:YAG as a saturable absorber, a maximum average output power of 1.82 W was achieved with the shortest pulse width of 18.2 ns at pulse repetition rate of 22.9 kHz. The single-pulse energy and pulse peak power were 79.4 μJ and 4.3 kW. This work has further verified that the Nd:SRA crystal is very promising for high-performance laser generation.

The hole injection capability is essentially important for GaN-based vertical cavity surface emitting lasers (VCSELs) to enhance the laser power. In this work, we propose GaN-based VCSELs with the p-AlGaN/p-GaN structure as the p-type hole supplier to facilitate the hole injection. The p-AlGaN/p-GaN heterojunction is able to store the electric field and thus can moderately adjust the drift velocity and the kinetic energy for holes, which can improve the thermionic emission process for holes to travel across the p-type electron blocking layer (p-EBL). Besides, the valence band barrier height in the p-EBL can be reduced as a result of usage of the p-AlGaN layer. Therefore, the better stimulated radiative recombination rate and the increased laser power are obtained, thus enhancing the 3 dB frequency bandwidth. Moreover, we also investigate the impact of the p-AlGaN/p-GaN structure with various AlN compositions in the p-AlGaN layer on the hole injection capability, the laser power, and the 3 dB frequency bandwidth.

We demonstrate an all-solid-state continuous-wave (CW) single-frequency tunable 1.08 µm laser, which is realized by employing a disordered laser medium Nd:CaYAlO4 (Nd:CYA) crystal. The maximal output power of single-frequency 1.08 µm laser is 1 W. By rotating the incident angle of the intracavity etalon (IE), the maximal tuning range of 183.71 GHz is achieved. After the IE is locked to the oscillating longitudinal mode of the laser, the continuous tuning range of 60.72 GHz for 1.08 µm laser is achieved by scanning the cavity length. To the best of our knowledge, this is the first demonstration of a CW single-frequency widely tunable 1.08 µm laser based on Nd:CYA crystal.

Conventional ultrashort pulsewidth measurement technology is autocorrelation based on second-harmonic generation; however, nonlinear crystals and bulky components are required, which usually leads to the limited wavelength range and the difficult adjustment with free-space light alignment. Here, we proposed a compact all-fiber pulsewidth measurement technology based on the interference jitter (IJ) and field-programmable gate array (FPGA) platform, without requiring a nonlinear optical device (e.g., nonlinear crystal/detector). Such a technology shows a wide measurement waveband from 1 to 2.15 µm at least, a pulsewidth range from femtoseconds to 100 ps, and a small relative error of 0.15%–3.8%. In particular, a minimum pulse energy of 219 fJ is experimentally detected with an average-power-peak-power product of 1.065×10-6 W2. The IJ-FPGA technology may offer a new route for miniaturized, user-friendly, and broadband pulsewidth measurement.

Cylindrical vector beams (CVBs), with non-uniform state of polarizations, have become an indispensable tool in many areas of science and technology. However, little research has explored high power CVBs at the femtosecond regime. In this paper, we report on the generation of high quality CVBs with high peak power and femtosecond pulse duration in a fiber chirped-pulse amplification laser system. The radially (azimuthally) polarized vector beam has been obtained with a pulse duration of 440 fs (430 fs) and a maximum average output power of 20.36 W (20.12 W). The maximum output pulse energy is ∼20 μJ at a repetition rate of 1 MHz, corresponding to a high peak power of ∼46 MW. The comparison between simulated intensity profiles and measured experimental results suggests that the generated CVBs have a remarkable intensity distribution. The proposed configuration of our laser system provides a promising solution for high quality CVBs generation with the characteristics of high peak power, ultrashort pulse duration, and high mode purity.

We report on a conceptually new type of waveguide in glass by femtosecond laser direct writing, namely, photonic lattice-like waveguide (PLLW). The PLLW’s core consists of well-distributed and densified tracks with a sub-micron size of 0.62 µm in width. Specifically, a PLLW inscribed as hexagonal-shape input with a ring-shape output side was implemented to converse Gaussian mode to doughnut-like mode, and high conversion efficiency was obtained with a low insertion loss of 1.65 dB at 976 nm. This work provides a new freedom for design and fabrication of the refractive index profile of waveguides with sub-micron resolution and broadens the functionalities and application scenarios of femtosecond laser direct-writing waveguides in future 3D integrated photonic systems.

A multi-lens retroreflector with field curvature compensation was designed and used in an alignment-free distributed-cavity laser with a long working distance for resonant beam charging applications. The multi-lens design, which makes use of off-the-shelf components, also allows a large field of view (FoV) without requirement of large element aperture. By implementing this design, an end-pumped 1063 nm Nd:GdVO4 laser could deliver over 5 W continuous-wave output power over a large range of working distances (1–5 m) and with ±30° receiver FoV under an incident diode pump power of 16.6 W. The output power fluctuation was less than 10% when moving and tilting the receiver over such a large range, without requiring any realignment of the cavity.

Direct current pulsed discharge is a promising route for producing high-density metastable particles required for optically pumped rare gas lasers (OPRGLs). Such metastable densities are easily realized in small discharge volumes at near atmospheric pressures, but problems appear when one is trying to achieve a large volume of plasma for high-power output. In this work, we examined the volume scalability of high-density metastable argon atoms by segmented discharge configuration. Two discharge zones attached with peaking capacitors were connected parallelly by thin wires, through which the peaking capacitors were charged and of which the inductance functioned as ballasting impendence to prevent discharging in only one zone. A uniform and dense plasma with the peak value of the number densities of Ar (1s5) on the order of 1013cm-3 was readily achieved. The results demonstrated the feasibility of using segmented discharge for OPRGL development.

Infrared (IR) thermal imaging has aroused great interest due to its wide application in medical, scientific, and military fields. Most reported approaches for regulating thermal radiation are aimed to realize IR camouflage and are not applicable to enhance thermal imaging. Here, we introduce a simple and effective method to process porous glass by femtosecond laser scanning, where distributed nanocavities and nanowires were produced, which caused improvement of the treated glass emissivity. The as-prepared sample possessed better IR thermal radiation performance but lower transmittance to visible light. We also demonstrated its applicability by placing it in different backgrounds, where the IR image temperature of laser-treated glass was closer to the actual environment, and this strategy may provide a new vision for enhanced thermal imaging.

When two synchronized laser beams illuminate the inner surface of bulk lithium niobate crystals with magnesium doping (5%/mol MgO:LiNbO3) under the condition of total reflection, semi-degenerate four-wave mixing (FWM) is generated. On this basis, a more sophisticated frequency conversion process on the interface of nonlinear crystal has been researched. The generation mechanism of FWM is associated with the fundamental waves reflected on the inner surface of the nonlinear crystal. Analysis of the phase-matching mechanism confirms that the FWM is radiated by the third-order nonlinear polarized waves, which are stimulated by the third-order nonlinear susceptibility coefficient of the nonlinear crystal. Theoretically calculated and experimentally measured corresponding data have been presented in this article. These results are expected to provide new inspiration for further experimental and theoretical research on frequency conversion in nonlinear crystals.

A novel infrared broadband nonlinear optical limiting (NOL) technology based on stimulated Brillouin scattering (SBS) in As2Se3 fiber is proposed. The As2Se3 fiber allows a weak infrared laser to pass through, but blocks an intense laser with the same wavelength due to the SBS effect. This NOL technology has been experimentally proved to have excellent NOL performance for incident pulsed lasers with a typical infrared wavelength of 3.6 µm. The linear transmissions of 1 m and 0.5 m As2Se3 fibers are higher than 90%, and the lowest nonlinear transmissions are reduced to 0.89% and 1.23%, respectively.

Nano-focusing structures based on hybrid plasmonic waveguides are likely to play a key role in strong nonlinear optical devices. Although the insertion loss is considerable, a significant nonlinear phase shift may be achieved by decreasing the nano-focusing device footprint and careful parameter optimization. Here, we study the Kerr effect in hybrid plasmonic waveguides by analyzing the mode effective area, energy velocity, and insertion loss. Particularly, by utilizing plasmonics to manipulate the effective index and mode similarity, the TM mode is reflected and absorbed, while the TE mode passes through with relatively low propagation loss. By providing a deep understanding of hybrid plasmonic waveguides for nonlinear applications, we indicate pathways for their future optimization.

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.

An AgGeSbTe thin film is proposed as a negative heat-mode resist for dry lithography. It possesses high etching selectivity with the etching rate difference of as high as 62 nm/min in CHF3/O2 mixed gases. The etched sidewall is steep without the obvious lateral corrosion. The lithographic characteristics and underlying physical mechanisms are analyzed. Besides, results of X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy further indicate that laser irradiation causes the formation of Ge, Sb, and AgTe crystals, which is the basis of etching selectivity. In addition, the etching selectivity of Si to AgGeSbTe resist is as high as 19 at SF6/Ar mixed gases, possessing good etching resistance. It is believed that the AgGeSbTe thin film is a promising heat-mode resist for dry lithography.

The near-infrared (NIR) emitting wavelength-tunable Cr3+-doped barium gallate (BGO:Cr) persistent luminescence (PersL) phosphors with enhanced luminescence were reported. The emission wavelength of the BGO:Cr PersL phosphors was adjusted from 715 to 739 nm by varying the amount of Cr3+ and the ratio of Ga:Ba. Meanwhile, the luminescence intensity and afterglow of the BGO:Cr PersL phosphors were enhanced. BGO:Cr PersL phosphors exhibited UV excitation, LED light restimulation, PersL for more than 6 days, and excellent capability for information storage, which was expected to promote the development of cheap and wavelength-tunable PersL materials for practical applications.

Quantum information technology requires bright and stable single-photon emitters (SPEs). As a promising single-photon source, SPEs in layered hexagonal boron nitride (hBN) have attracted much attention recently for their high brightness and excellent optical stability at room temperature. In this review, the physical mechanisms and the recent progress of the quantum emission of hBN are reviewed, and the various techniques to fabricate high-quality SPEs in hBN are summarized. The latest development and applications based on SPEs in hBN in emerging areas are discussed. This review focuses on the modulation of SPEs in hBN and discusses possible research directions for future device applications.

An autostereoscopic display system with a bicylindrical lens based on temporal-spatial multiplexing technique is introduced in this paper. The system comprises a directional scanning backlight, a liquid crystal display panel with high refreshing rate, and an eye tracking device. The directional scanning backlight consists of an LED board, two lenticular lens arrays with matching periods, a parallax barrier film, and other optical films. One of the lenticular lenses is a bicylindrical lens designed to reduce aberration, hence achieving better image quality. A prototype is set up based on the proposed structure. A series of experiments are conducted, and the overall performance of the prototype is evaluated. The LEDs are divided into 10 groups that form 10 view zones. On the one hand, it achieves full resolution in both 2D and 3D display modes. On the other hand, the viewing angle is increased to ±26 deg. Most importantly, the crosstalk is low. The minimum crosstalk is 6%, and the maximum crosstalk is 8.8% at a viewing angle of ±22 deg.

At present, reconstruction of megapixel and high-fidelity images with few measurements is a major challenge for X-ray ghost imaging (XGI). The available strategies require massive measurements and reconstruct low-fidelity images of less than 300×300 pixels. Inspired by the concept of synthetic aperture radar, synthetic aperture XGI (SAXGI) integrated with compressive sensing is proposed to solve this problem with a binned detector in the object arm. Experimental results demonstrated that SAXGI can accurately reconstruct the 1200×1200 pixels image of a binary sample of tangled strands of tungsten fiber from 660 measurements. Accordingly, SAXGI is a promising solution for the practical application of XGI.