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Ways to lessen re-ankylosis within temporomandibular joint ankylosis people.
Fourier analysis of interferograms captured in white light interference microscopy is proposed for performing simultaneous local spectral and topographic measurements at high spatial resolution over a large field of view. The technique provides a wealth of key information on local sample properties. We describe the processing and calibration steps involved to produce reflectivity maps of spatially extended samples. This enables precise and fast identification between different materials at a local scale of 1 µm. We also show that the recovered spectral information can be further used for improving topography measurements, particularly in the case of samples combining dielectric and conducting materials in which the complex refractive index can result in nanometric height errors.The absorbance of a free-standing ultrathin layer is limited to 50%; we overcome this limitation by numerically investigating a wavelength-selective perfect absorber based on Mie resonance and degenerate critical coupling. We extend the wavelength of close-to-unity absorbance to the entire visible region by controlling the radiative loss and intrinsic loss. Radiative loss can be controlled by embedding the Mie resonator into a thin film with the defined refractive index. Meanwhile, intrinsic loss can be controlled by addition of a dielectric cap with a higher extinction coefficient on the Mie resonator. Such all-dielectric perfect absorbers can be applied to efficient photodetectors, imaging sensor pixels, or all-optical switching devices mediated by the photothermal effect.Beam engineering is one of the most important functionalities in light detection and ranging (LiDAR). In this work, a silicon optical phased array (OPA) is employed to control the beam profile. Machine-learning-based genetic algorithm optimization is utilized to suppress the sidelobes of the far field pattern assuming the random distribution of aperiodic arrays. The optimized mainlobe position versus wavelength relationship in two-dimensional aperiodic arrays is distinctly different from prior works. Analysis was performed to show the effect of fabrication error of arrays on the side mode suppression ratio. Our study provides an effective pathway to optimize the random distributed OPAs within a controllable time frame among the vast number of parameters.A new, to the best of our knowledge, output coupler (OC) with enhancement of the cavity reflectivity is proposed to remarkably elevate the output powers and efficiencies of diode-pumped NdGdVO4/KGW Raman yellow-orange lasers. The cavity reflectivity is effectively increased by using the double-sided dichroic coating on the OC. In comparison with the conventional single-sided coating, the conversion efficiency can be boosted from 15% to 26.3% in the experiment of a yellow laser at 578.8 nm, and the maximum output power can be increased from 5.7 to 10.5 W in the quasi-continuous-wave mode with 50% duty cycle and frequency of 500 Hz. Furthermore, in the operation of an orange laser at 588 nm, the maximum output power can be improved from 5.6 to 7.0 W by replacing the conventional OC with the new one.A novel, to the best of our knowledge, sensing approach based on scanning white-light interferometry (SWLI) is proposed to detect piston errors of the multi-aperture optical telescope. The scanning white-light interferometer is composed of a Mach-Zehnder interferometer (MZI) and an optical path modulator (OPM). A lenslet array is used to image the interferometric wavefront between the reference and the other individual apertures. The piston errors can be estimated from these SWLI signals focused by the lenslet array. The measurement range of the proposed method depends on the modulation range of the OPM and can reach millimeter order, and its accuracy is better than a 1/20 wavelength. In addition, the proposed method's amplitude-splitting interferometry of the MZI makes it fit for a multi-aperture optical telescope. We demonstrate a proof of concept and validate the feasibility of our proposed phasing method.Dynamic strain sensing over a frequency range from 0.01 to 20 Hz can be used for monitoring earthquakes and volcanoes, charting rock and petroleum formations beneath the earth. However, significant laser frequency drifting (LFD) has limited the detection in this frequency range, especially for distributed frequency detection with phase optical time domain reflectometry (OTDR), where the LFD will introduce a time dependent noise destroying the dynamic strain reconstruction. In this study, a simple and effective method that utilizes the referenced random fiber grating to monitor the variation of laser frequency has been both theoretically analyzed and experimentally demonstrated. During the maximum up to 200 s data acquisition time, the frequency variation of a distributed feedback (DFB) laser with MHz linewidth is obtained from the referenced portion of sensing signal, and then the 1 Hz and 0.01 Hz dynamic strain variations with amplitude of 30 µε are reconstructed with strain measurement standard deviation of 66 nε. Due to signal-to-noise ratio (SNR) enhanced Rayleigh traces from random fiber gratings, a minimum detectable frequency drifting of 7.28 MHz could be achieved over the optical frequency of 2×1014Hz.We demonstrate the tunable difference frequency generation (DFG) of an oxide La3Ga5.5Nb0.5O14 (LGN) crystal pumped by near-infrared lasers with nanosecond pulses for the first time to our knowledge. The type I and II phase-matching conditions of DFG were calculated in the mid-infrared region. With the processed LGN crystals, tunable lasers in the wavelength range from 4.4 to 5.7 µm and 4.56 to 5.6 µm were achieved under type II and I phase-matching conditions, respectively, with the maximum output energy of 13.1 µJ, which agreed well with the theoretical calculation. This work provides the kind of promising mid-infrared nonlinear crystals for the pumping of nanosecond pulsed lasers as well as a tunable mid-infrared laser source at a wavelength over 5 µm in further photonic applications.Spectral contrast, the ability to measure frequency components of vastly different intensity, is critical in optical spectroscopy. For high spectral contrast at high spectral resolution, scanning etalons are generally used, as they allow cascading multiple dispersive elements. However, scanning instruments are inherently limited in terms of acquisition speed. Here we report a single-shot cascaded spectrometer design, in which light is dispersed along a single dispersion direction at every stage and thus can be recirculated in the same etalon multiple times. Using this design principle, we demonstrate single-shot spectral measurements at sub-gigahertz resolution and unprecedented spectral contrast (∼80dB).Inorganic halogen perovskite quantum dots not only have high fluorescence quantum efficiency, but also can emit polarized light in solution or thin film. These excellent performances make perovskite quantum dots promising to be used in next-generation displays. In this study, we develop laser direct writing technology to improve the emitted light polarization of CsPbClBr2 quantum dot film. Without using an additional polarizer, we prove that the polarization degree is maximumly increased by about 56%, and the reasons are analyzed from three perspectives laser scanning space, laser power, and film thickness. In addition, the lifetime of the fluorescence is also greatly improved after laser treatment. The results we obtain provide the possibility for production of a new generation of displays.We report a novel, to the best of our knowledge, way to achieve phase-controlled dual-wavelength resonance based on whispering-gallery-mode (WGM) microcavities experimentally. With the help of a feedback waveguide, not only two optical pathways but also a unidirectional coupling between counter-propagating waves are formed, which is the requirement of all-optical analogues of electromagnetically induced transparency and Autler-Townes splitting. By adjusting the accumulating phase introduced from the fiber waveguide, we observe the signal lineshape changes from symmetric to asymmetric, i.e., the resonant transmission and extinction ratio of two splitting modes can be controlled, which brings a new degree of freedom to the WGM resonator system. These results may boost the development of quantum state control and pave the way for reconfiguring devices such as narrow-band filters.We investigate a novel concept of cascaded single side band (SSB) comb generation for improving the carrier-to-noise ratio (CNR), which degrades when the bandwidth of the SSB comb becomes wider. Wavelength-multiplexed seed lasers are simultaneously modulated in a recirculating frequency shifter loop with an SSB modulator, an Er-doped fiber amplifier, and a fiber Bragg grating whose reflective notch filter nature enables seed lasers to be synchronized through the injection locking (IL). A maximum CNR improvement of 11.3 dB is experimentally demonstrated under the IL condition. The proposed technique effectively improves the CNR of wide-bandwidth SSB combs.We propose to use exceptional points (EPs) to construct diffraction-free beam propagation and localized power oscillation in lattices. We specifically consider two systems to utilize EPs for diffraction-free beam propagation, one in synthetic gauge lattices and the other in unidirectionally coupled resonators where each resonator individually is capable of creating orbital angular momentum (OAM) beams. In the second system, we introduce the concept of robust and tunable OAM beam propagation in discrete lattices. We show that one can create robust OAM beams in an arbitrary number of sites of a photonic lattice. Furthermore, we report power oscillation at the EP of a non-Hermitian lattice. Our research widens the study and application of EPs in different photonic systems including OAM beams and their associated dynamics in discrete lattices.We theoretically investigated the vector properties of quartic solitons in a pure fourth-order-dispersion birefringent fiber and a quartic-dispersion-dominant mode-locked fiber laser. We found that, compared with scalar pure quartic solitons, a vector quartic soliton (VQS) in the birefringent fiber still preserves the Gaussian shape, except for the distinctions of reduced peak power, central frequency offset, slight frequency chirp, and mitigated oscillatory tails. We also demonstrated that pulse shaping in the mode-locked laser cavity could explicitly facilitate the formation of Kelly sidebands and distortion of oscillatory tails. Furthermore, dynamical evolutions of quartic group-velocity-locked and polarization-rotating vector solitons were obtained to enrich the nonlinear community of VQSs. We believe that our elaborate findings will bring insights into both the fundamental understanding and potential applications of VQSs.The employment of coherent detection in a Brillouin optical time domain analysis (BOTDA) fiber sensor brings benefits, including signal-to-noise ratio enhancement, non-local effect reduction, and sensing speed improvement. Recently, it was found that the performance of a coherent-detection BOTDA fiber sensor suffers from phase fluctuations introduced by the fiber group delay jitter. buy UNC1999 Here, we propose a phase fluctuation cancellation approach based on optical subcarrier multiplexing. In a proof-of-concept experiment, the phase stability for in-phase/quadrature demodulation reaches a standard deviation value of as small as 0.4 mrad. The variations in the Brillouin gain and phase spectra caused by the phase fluctuation are then effectively alleviated, resulting in an enhancement of the Brillouin frequency shift measurement certainty along the whole sensing fiber.
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