In near-infrared imaging and spectroscopy, high-fidelity modeling of photon transport for dense polydisperse colloidal suspensions is crucial. We developed photon transport models using the radiative transfer equation (RTE) with the dependent scattering theory (DST) at volume fractions up to 20%. The polydispersity and interference effects strongly influence results of the scattering properties and the RTE in cases of small mean diameter and large variance of the particle size distribution. We compared the RTE-results for the Henyey-Greenstein (conventional) function with those for the phase function using the DST. The RTE-results differ between both functions at low volume fractions for forward scattering media, suggesting the limitation of the conventional function.We present a femtosecond laser-based interferometry for step-structure surface measurement with a large field of view. A height axial scanning range of 348 µm is achieved by using the method of repetition frequency scanning with reference to the Rb atomic clock and the optical path length difference design for 21 times of the pulse interval. A combined method, which includes the envelope peak positioning method for rough measurement, synthetic-wavelength interferometry for connection, and carrier wave interferometry for fine measurement, is proposed to reconstruct the surface. A three-step specimen with heights of approximately 20, 50, and 70 µm was successfully measured with a height precision of 7 nm, and the accuracy was verified by a commercial white light interferometer. The diameter of the field of view that was demonstrated was 17.3 mm, which could be much larger owing to the high spatial coherence of the femtosecond laser. The results show that the femtosecond laser system combines the step-structure measurement performance of white light interferometry and the high-precision large-field performance of phase shifting interferometry, indicating its potential for widespread use in ultra-precision manufacturing of micro/nano-devices, such as semiconductor chips, integrated circuits, and micro-electro-mechanical systems.We propose a wide-range strain sensor based on Brillouin frequency and linewidth in a 50 cm-long As2Se3-polymethyl methacrylate (As2Se3-PMMA) hybrid microfiber with a core diameter of 2.5 µm. The distributed information over the hybrid microfiber is measured by a Brillouin optical time-domain analysis (BOTDA) system. The wide dynamic range strain from 0 to 15000 µɛ is enabled by measuring the Brillouin frequency and linewidth due to the low Young's modulus of As2Se3 core and the high mechanical strength of PMMA cladding. The deformation of the As2Se3-PMMA hybrid microfiber is observed when the strain is greater than 1500 µɛ by measuring the distributed Brillouin frequency and Brillouin linewidth over the 50 cm-long hybrid microfiber. The measured errors based on the Brillouin frequency in the range of 0-1500 µɛ and 1500-15000 µɛ are 42 µɛ and 105 µɛ, respectively. The measured error based on the Brillouin linewidth is 65 µɛ at 0-1500 µɛ and the maximum error is 353 µɛ when the tensile strain is 15000 µɛ. No strain memory effect is observed compared with the polymer optical fiber due to Young's modulus in As2Se3 is larger than that in polymer.  https://www.selleckchem.com/  Numerical simulations are developed to accurately predict the strain dependence of Brillouin frequency in the As2Se3-PMMA hybrid microfiber.Collinear phase matching of the Stokes ↔ anti-Stokes interaction for Raman-active crystals with different birefringence was studied theoretically as well as experimentally. It was shown that collinear phase matching of the Stokes ↔ anti-Stokes interaction in low-birefringent crystals can be insensitive to angular mismatch if a phase matching angle is higher than 60°. We have developed and experimentally realized an extracavity parametric Raman anti-Stokes laser based on a low-birefringent SrWO4. Cyan 507-nm anti-Stokes conversion from green (532 nm) pump radiation of a 5-ns, 1-mJ second harmonic NdYAG laser has been obtained. Laser setup with a single beam excitation made it possible to use an output face of the SrWO4 crystal as an output coupler because of wide (6°) angular tolerance of collinear phase matching that resulted in an increase of slope efficiency of anti-Stokes generation higher than 3% at the anti-Stokes energy output of a 10-µJ level.In this paper, AlInN nanowire ultraviolet light-emitting diodes (LEDs) with emission at ∼299 nm have been successfully demonstrated. We have further studied the light extraction properties of these nanowire LEDs using photonic crystal structures with square and hexagonal lattices of nanowires. The light extraction efficiency (LEE) of the periodic nanowire LED arrays was found to be significantly increased as compared to random nanowire LEDs. The LEEs reach ∼ 56%, and ∼ 63% for the square and hexagonal photonic crystal-based nanowire structures, respectively. Moreover, highly transverse-magnetic polarized emission was observed with dominant vertical light emission for the AlInN nanowire ultraviolet LEDs.A high performance compact silicon photonics polarization splitter is proposed and demonstrated. The splitter is based on an asymmetric directional coupler. High extinction ratios at the through and drop ports of the polarization splitter are achieved by using an on-chip TE-pass polarizer and a TM-pass polarizer, respectively. The splitter, implemented on a silicon-on-insulator platform with a 220 nm-thick silicon device layer, has a measured insertion loss lower than 1 dB (for both TE and TM modes) and extinction ratio greater than 25 dB (for TM mode) and greater than 36 dB (for TE mode), in the wavelength range from 1.5 µm to 1.6 µm. The footprint of the device is 12 µm × 15 µm.Self-assembled plasmonic metasurfaces are promising optical platforms to achieve accessible flat optics, due to their strong light-matter interaction, nanometer length scale precision, large area, light weight, and high-throughput fabrication. Here, using photothermal continuous wave laser lithography, we show the spectral and spatial tuning of metasurfaces comprised of a monolayer of ligand capped hexagonally packed gold nanospheres. To tune the spectral response of the metasurfaces, we show that by controlling the intensity of a laser focused onto the metasurface that the absorption peak can be reconfigured from the visible to near-infrared wavelength. The irreversible spectral tuning mechanism is attributed to photothermal modification of the surface morphology. Combining self-assembled metasurfaces with laser lithography, we demonstrate an optically thin (λ/42), spectrally selective plasmonic Fresnel zone plate. This work establishes a new pathway for creating flat, large area, frequency selective optical elements using self-assembled plasmonic metasurfaces and laser lithography.