Theoretical analysis of the electromagnetic field distribution in the focal region of a long metallic parabolic reflector that has its surface covered with a magnetized plasma layer is derived. The incident wave is considered to be with a general oblique incidence for both parallel and perpendicular polarizations. The electromagnetic field intensity expressions along the focal region are obtained accurately using Maslov’s method. The effects of plasma thickness on the reflected and transmitted field distributions are investigated. The effects of other physical parameters such as the angle of incidence and the plasma and cyclotron frequencies on the transmitted field-intensity distribution along the focal region are also studied. The results obtained by Maslov’s method and Kirchhoff’s approximation are found to be in a good agreement.

We report a locking mode in which the local oscillator (LO) is locked to an atomic fountain and calibration of the residual frequency drift (RFD). In this running mode, the locked LO outputs a standard frequency signal, and a short-term fractional frequency stability of 2.7×10 13τ 1/2 is achieved. Due to the frequency drift of the LO in free running mode, a systematic frequency bias, or RFD, exists after being locked by the atomic fountain. We analyze and measure the RFD with a value of 3(2)×10 16. A sectionalized post-process method is adopted to calibrate the RFD.

To determine the amplitude of weak sinusoidal water surface acoustic wave (WSAW), a method based on the spectrum analysis of the phase-modulated interference signal is developed. Calculated from the amplitude spectrum of the detection signal, a characteristic ratio indicates that the phase-modulation depth of a WSAW is suggested by determining the amplitude of a WSAW according to their functional relationship. Experimental investigations for a 4 kHz WSAW evaluate the measurement’s precision with an amplitude measurement standard deviation of 0.12 nm. The measurement accuracy also is demonstrated by the experimental investigations. The theory of this method is briefly described, and the experimental setup is presented.

Through employing permutation entropy and the self-correlation function, the time-delay signature (TDS) of a vertical-cavity surface-emitting laser (VCSEL) with variable-polarization filtered optical feedback (VPFOF) is evaluated theoretically. The work shows that the feedback rate η, polarizer angle θp, and filter bandwidth Λ have an obvious influence on the TDS. The evolution maps of the TDS in parameter space (η,Λ) and (η,θp) are simulated for searching the chaos with weak TDS. Furthermore, compared with a VCSEL with polarization-preserved filtered optical feedback and a VCSEL with variable-polarization mirror optical feedback, this VPFOF–VCSEL shows superiority in TDS suppression.

We report a wavelength swept fiber laser at the 1 μm region based on an actively mode-locked dispersion-tuning technique. The ring-cavity laser uses a 70 cm ytterbium-doped fiber as a gain medium. Mode locking is achieved by the direct modulation of the amplitude modulator, and a ～1000 m single-mode fiber is used to provide the desired intracavity dispersion. By sine-modulating the modulation frequency, a wavelength swept laser with a range of ～30 nm can be achieved at a sweeping rate of 50 Hz. The characteristics of the laser, such as its single-wavelength tuning range, tuning sensitivity, static linewidth and sweeping rate, are also studied experimentally.

Nanosecond single- and multiple-pulse laser damage studies on HfO2/SiO2 high-reflection (HR) coatings are performed at 532 nm. For single-pulse irradiation, the damage is attributed to the defects and the electric intensity distribution in the multilayer thin films. When the defect density in the irradiated area is high, delamination is observed. Other than the 1064 nm laser damage, the plasma scalding of the 532 nm laser damage is not pits-centered for normal incidence, and the size of the plasma scalding has no relation to the defect density and position, but increases with the laser fluence. For multiple-pulse irradiations, some damage sites show deeper precursors than those from the single-shot irradiation due to the accumulation effects. The cumulative laser-induced damages behave as pits without the presence of plasma scalding, which is unaffected by the laser fluence and shot numbers. The damage morphologies and depth information both confirm the fatigue effect of a HfO2/SiO2 HR coating under 532 nm laser irradiation.

A theoretical model of a nonlinear hyperbolic metamaterial is presented in the form of a stack of subwavelength layers of linear plasmonic and nonlinear dielectric materials. A broad picture of the properties of evanescent waves (high-k modes) in this stack is investigated by plotting global transmission diagrams. The presence of nonlinearity strongly modifies these diagrams. The emergence and modification of nonlinear evanescent waves is observed. Some signatures of nonlinear phenomenon such as formation of orbits and trajectories around fixed points are also seen in our work.

For the development of fiber optics for the range from 0.2 to 50.0 μm, one needs light-stable, nonhygroscopic, ductile crystals that would be transparent within this spectral range and have a lack of cleavage, and from which the flexible infrared (IR) fibers are extruded. The crystals based on solid solutions of silver and monadic thallium halides meet the conditions listed above. Consequently, by differential thermal and x ray analyses, we study the TlBr–TlI phase diagram using the crystals with optimal compositions, which we grow ourselves. We also manufacture light-stable nanocrystalline IR fibers that are transparent at longer wavelengths compared with AgCl–AgBr fibers.

By studying the thermal-induced phase shift mechanism of an interferometric fiber-optic gyroscope (IFOG) sensing coil, a novel generalized expression based on a three-dimensional (3D) model is proposed. Compared with the traditional pure Shupe effect model, the simulation results show that the new 3D model, including elastic strain and the elasto-optical effect, can describe the thermal effect of the coils more accurately. Experiments with temperature change rates between 40°C and 70°C are performed to verify the effectiveness of the proposed generalized expression. The results of our work can guide researchers in identifying countermeasures to reduce the thermal-induced bias error in IFOG.

The appearance of blood vessels is an important biomarker to distinguish diseased from healthy tissues in several fields of medical applications. Photoacoustic microangiography has the advantage of directly visualizing blood vessel networks within microcirculatory tissue. Usually these images are interpreted qualitatively. However, a quantitative analysis is needed to better describe the characteristics of the blood vessels. This Letter addresses this problem by leveraging an efficient multiscale Hessian filter-based segmentation method, and four measurement parameters are acquired. The feasibility of our approach is demonstrated on experimental data and we expect the proposed method to be beneficial for several microcirculatory disease studies.

A scheme is presented to generate atomic entanglement by detecting the transmission spectrum of a coupled-cavity system. In the scheme, two 3-level atoms are trapped in separate cavities coupled by a short optical fiber, and the atomic entanglement could be realized in a heralded way by detecting the transmission spectrum of the coupled-cavity system.

Glass ceramics Ba2LaF7:xDy3+ are obtained through the conventional melt-quenching technique, and their luminescent properties are investigated. Under 350 nm excitation, the emission spectra consists of a strong blue-yellow band as well as a weak red emission centered at 660 nm, which are attributed to the F9/24→H15/26, F9/24→H13/26 and F9/24→H11/26 transitions of the Dy3+ ion, respectively. The corresponding Commission Internationale de L’Eclairage (CIE) chromaticity coordinate for a sample of 2 mol.% Dy2O3 after being heat-treated at 690°C is (0.313, 0.328). It is concluded that the formed materials may have the possibility of applications for white light-emitting diodes (LEDs).

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.

We present a tabletop-scale spotlight-mode down-looking synthetic aperture imaging ladar (DL SAIL) demonstrator, which is performed by a collimator with 10 m focal length to simulate the far-field optical field. A specular-point target and a diffuse-reflection target have been used for resolution analysis and 2D imaging, respectively. The experimental result is in agreement with the theoretical design. The experiment setup is capable of simulating a real application scenario for further study. This Letter is focused on the proposition and implementation of spotlight-mode DL SAIL.

A novel and simple polarization independent grating couplers is designed and analyzed here, in which the TE polarization and the TM polarization light can be simultaneously coupled into a silicon waveguide along the same direction with high coupling efficiency. For the polarization-insensitive grating coupler, the coupling efficiencies of two orthogonal polarizations light are more than 60% at 1550 nm wavelength based on our optimized design parameters including grating period, etching height, filling factor, and so on. For TE mode the maximum efficiency is ～72% with more than 30 nm 1 dB bandwidth, simultaneously, for TM mode the maximum efficiency is 75.15% with 40 nm 1 dB bandwidth. Their corresponding wavelength difference between two polarizations’ coupling peaks is demonstrated to be 35 nm. Polarization independent grating coupler designed here can be widely used in optical communication and optical information processing.

In order to realize homodyne reception and Doppler frequency shift tracking in ground-to-satellite coherent laser communication, a local laser is experimentally demonstrated in this Letter. It is realized based on modulation-sideband injection locking, and has a 10 GHz tuning range, a 1 THz/s tuning rate, a 5 kHz linewidth, and 16 mW of output power. When applied to a Costas loop in a coherent laser communication system, the local laser can achieve ±5 GHz Doppler frequency shift tracking with a 20 MHz/s frequency shift rate, which is sufficient for the ground-to-satellite coherent laser communication.

A method of chromatic polarization imaging is presented for the online detection of colorless plastic contaminants from ginned cotton in an industrial setting. To understand the experimental results, we consider a realistic microscopic model, including the multiple scattering of anisotropic fibers and the light propagation in anisotropic slabs. A Monte Carlo code, based on the extended Jones matrix, is developed to simulate photon migration with polarization states, and phase information followed. Using simulations and experiments, we analyze the underlying mechanisms and evaluate the performance of this method with different layer thicknesses. Our approaches proposed in this Letter also have the potential to be applied in tissue imaging, remote sensing, and other scenarios.

We demonstrate theoretically and experimentally how changes of a terahertz (THz) beam induced by the sample affect the accuracy of the determination of THz dielectric properties in THz time-domain transmission spectroscopy (TDTS). We apply a Gaussian beam and the ABCD matrix formalism to describe the propagation of the THz beam in a focused beam setup. The insertion of the sample induces a focus displacement which is absent in the reference measurement without a sample. We show how the focus displacement can be corrected. The THz optical properties after focus displacement correction reported in this Letter are in quantitative agreement with those obtained using collimated beam THz–TDTS in previous work.

In this Letter, a new, constrained color-matching algorithm that removes the color variations is presented, in which all the color gamut of the projectors is mapped into a common gamut that can be produced by all the devices in the system. The smoothness constraints on the difference between two adjacent pixels are taken into account to calculate the luminance attenuation map of each pixel in the overlapping region to achieve luminance seamlessness. The experimental results demonstrate the validity and superiority of this correction algorithm.

A tomography device based on a conventional laboratory x ray source, polycapillary parallel x ray lens (PPXRL), and polycapillary collimating x ray lens (PCXRL) is designed. The PPXRL can collect the divergent x ray beam from the source and focus it into a quasi-parallel x ray beam with a divergence of 4.7 mrad. In the center of quasi-parallel x ray beam, there is a plateau region with an average gain in power density of 13.8 and a diameter of 630 μm. The contrast of the image can be improved from 28.9% to 56.0% after adding the PCXRL between the sample and the detector.