Abstract: A distributed fiber-optic acoustic sensing system and a signal processing method. The distributed fiber-optic acoustic sensing system is based on a high spatial resolution distributed fiber-optic acoustic sensor. The interval between adjacent sensing units is centimeter or millimeter level. Through specific digital signal processing, signal enhancement can be realized, noise in the system and environment are suppressed, at the same time, problems such as interference fading is solved, and the sensor signal-to-noise ratio of subunits can be increased by two to three orders of magnitude. Each subunit can serve as an independent high-sensitivity sensor for sensing. The multiple subunits can form one or more new sensor arrays. The azimuth estimation and spatial orientation of signal sources can be realized by the array signal processing method.

Abstract: A resistance spot welding electrode cap contains a groove at the center of the welding contact interface. During welding, because of the groove, the area of contact between the electrode cap and a metal workpiece to be soldered is reduced. In the initial stage, the overall heat generation is concentrated on the outer ring of the weld point and heat dissipation becomes slower, helping a weld nugget to form from the outside to the inside. Due to the presence of the groove, the metal workpiece expands toward the groove at the center of the electrode, thereby increasing the size of the weld nugget and reducing splash and deformation. In comparison with conventional electrode caps, the welding current required to form weld points of the same size is lower, saving on electricity costs, and weld points obtained using the same current have higher strength and stability with fewer welding defects.

Abstract: A laser driving device and a method for enabling a uniform light field, wherein the laser driving device is a high-power laser driving device that enables a uniform light field on the basis of a narrow-band low-spatial-coherence light and is provided for laser fusion. The narrow-band low-spatial-coherence light is configured as a seed of the laser driving device, an amplification and transmission unit amplifies the seed, a frequency conversion unit converts a frequency of the laser, and a focusing component is configured for laser focusing and uniform illumination.

Abstract: A simultaneous phase-shift point diffraction interferometer and method for detecting wave aberration. The interferometer comprises an ideal spherical wave generation module, an optical system to be measured, an image plane mask, a polarization phase shift module, a two-dimensional polarization imaging photodetector and a data processing unit. Single photodetector is adopted to realize simultaneous detection of more than three phase shift interference patterns, and has the advantages that environmental interference suppression, a flexible optical path, high measurement accuracy, and calibration of system errors of the interferometer may be realized.

Abstract: A photodarkening-resistant ytterbium-doped quartz optical fiber and a method for prpearing such a fiber are provided. Glass of a photodarkening-resistant ytterbium-doped quartz optical fiber core rod includes at least Yb2O3, Al2O3, P2O5, SiO2. The proportions of Yb2O3, Al2O3, and P2O5 in the entire substance are Yb2O3: 0.05-0.3 mol %, Al2O3: 1-3 mol %, and P2O5: 1-5 mol %, respectively. In the preparation method for the photodarkening-resistant ytterbium-doped quartz optical fiber, a sol-gel method and an improved chemical vapor deposition method are combined. By using the molecular-level doping uniformity and the low preparation loss thereof respectively, ytterbium ions, aluminum ions and phosphorus ions are effectively doped in a quartz matrix, thereby effectively solving the problems in the optical fiber of high loss, photodarkening caused by cluster or the like, and a central refractive index dip.

Abstract: Provided are an integrated super-resolution laser direct-writing device and a direct-writing method. The integrated super-resolution laser direct-writing device includes a first continuous laser, a first optical fiber coupler, a mono-mode optical fiber, a second continuous laser, a second optical fiber coupler, a first annular photonic crystal fiber, a bifurcated optical fiber, a lens group, a first dichroic mirror, an LED light source, a lens, a second dichroic mirror, an auto-focusing module, a third dichroic mirror, a third optical fiber coupler, a square-law graded index fiber, a nanometer displacement table, a second lens, a CMOS camera and a control system. According to the present invention, an original large direct-writing device based on a free optical path can achieve optical fibers of key devices and integration of systems and can be better applied to the field of laser direct-writing.

Abstract: A single-shot Fresnel non-coherent correlation digital holographic device based on a polarization-oriented planar lens, comprising: A polarization-oriented planar lens (1) for wavefront modulation and beam splitting, a focusing element (2), a half-wave plate (3) with a small hole and a polarization imaging camera (4). Incident light passes through the polarization-oriented planar lens (1) and the focusing element (2) and is divided into two beams with different polarizations, that is, focused and parallel or focused and divergent beams, wherein the focused beam passes through the small hole of the half-wave plate (3), the parallel or divergent beam passes through the half-wave plate (3), so as to make the polarization of the two beams consistent behind pass through the half-wave plate (3).

Abstract: Apparatus and method for detecting wavefront aberration of an objective lens, comprising a wavefront detection system, a planar mirror, and a planar mirror adjusting mechanism; the objective lens is placed between planar mirror and wavefront detection system; planar mirror is positioned at focal point of the objective lens. A test wavefront emitted by wavefront detection system passes through the objective lens, gets reflected by the planar mirror, and t passes through the objective lens again; the wavefront detection system receives and detects the test wavefront to derive a phase distribution thereof; an angle of the planar mirror tilts at is adjusted to obtain different return wavefronts; a polynomial for expressing wavefront aberration is selected, and expressions corresponding to all the return wavefronts are calculated; result of fitting the wavefront aberration of the objective lens when expressed by the selected polynomial is derived through fitting with the polynomial.

Abstract: A multi-channel device and method for measuring the distortion and magnification of objective lens. The multi-channel device for measuring the distortion and magnification of objective lens comprises an illumination system, a reticle stage, a test reticle, a projection objective lens, a wafer stage and a multi-channel image plane sensor, wherein the multi-channel image plane sensor simultaneously measures the image placement shifts between actual image points and nominal image points after a plurality of object plane test marks are imaged by the projection objective lens, and calculates the distortion and magnification errors of the objective lens by fitting, which shortens the measurement time, eliminates the influence of wafer stage errors on the measurement accuracy and improves the measurement accuracy.

Abstract: Laser ablation processing method for debris-free and efficient removal of materials comprises the step of using a refrigeration device to condense the water vapor and form a thin frost layer on the materials at temperatures below the freezing point. The residual debris produced during the ablation process deposits on the frost layer that covers the material, which is easily removed when the frost layer melts. At the same time, the frost layer in the laser irradiation area melts to a liquid layer, which can effectively reduce the deposition of debris on the inner wall of the groove and thus improve the efficiency and quality of laser ablation. The method is applicable to debris-free laser processing on an arbitrary curved surface.

Abstract: Method for simultaneously compensating pupil coordinate distortion and shear amount change in a process of wavefront reconstruction in grating transverse shear interference. Where a wavefront is diffracted by a grating, the shapes and light paths of the diffracted wavefronts of all the orders are different, so that on one hand, a coordinate system detected by a detector plane is distorted relative to a pupil coordinate system, and on the other hand, a shear amount changes along with a coordinate position.

Abstract: An apparatus and method herein efficiently couple spatial light to optical fiber light for achieving stability of an optical axis without a position sensor. The basic concept of the method includes: first, obtaining, according to a theoretical coupling efficiency model, a model parameter by means of fitting calculation; second, using a four-point tracking algorithm to calculate an optical fiber nutation trajectory according to the optical fiber nutation principle; and finally, using the nutation trajectory to calculate the position deviation of a central point. The optical axis is ensured to be stable by correcting the position deviation, and the high coupling efficiency remains. The method is used for the stability of the optical axis in a space coherent laser communication DPSK link. The high efficiency coupling is a key technology of long-distance, high bit rate transmission in space laser communication, and is significant in the development of inter-satellite optical communications.

Abstract: A high laser damage threshold reflective optically addressed liquid crystal spatial light modulator for shaping 1053 nm linearly polarized light beams, comprising a computer-controlled LCoS electrical addressable spatial light modulator, polarization beam splitter, and polarizer, Liquid crystal cell, analyzer, AC power supply, where the liquid crystal cell comprises a transparent conductive film antireflection film layer, a transparent conductive film base layer, a first transparent conductive layer, a liquid crystal alignment layer, a liquid crystal layer, an alignment element, a reflective film layer, a light guide layer, and a second transparent conductive layer. By changing the transparent conductive layer material of the light-transmitting part of the liquid crystal cell from ITO to gallium nitride material, the damage threshold of the high-energy laser is improved, which facilitates application of beam shaping in high-power laser devices.

Abstract: A pyramidal growth method for long-seed KDP-type crystal. In the growth method provided by the present invention, the lower end of the long-seed crystal is restricted by a lower tray, and the upper end is free to grow into a pyramidal. At the same time, the four prismatic faces at two directions of [100] and [010] can grow, avoiding growth stress problem during crystal growth, and all cut optical elements have high optical quality. Because the growth process is that four prismatic faces with highly similar growth environments grow at the same time and stirring is applied by blade-like stirring paddles during the crystal growth process, the cut optical elements have high optical uniformity.

Abstract: A laser radar system apparatus for the multi-wavelength measurement of the atmospheric carbon dioxide concentration and a vertical aerosol profile, including: a laser transmitting unit; a dual-pulse laser capable of simultaneously transmitting laser having three wavelengths, i.e., 1572 nm, 1064 nm, and 532 nm; a transmitting beam expander; a receiving telescope system; a visual axis monitoring module; a photoelectric detection unit; and a data acquisition and processing unit. The laser that simultaneously outputs laser having three wavelengths is used in a laser radar system, and an optical differential absorption method and a high spectral resolution detection method are used, such that the atmospheric carbon dioxide concentration and the vertical aerosol profile can be measured simultaneously and high-precision aerosol monitoring is implemented during the high-precision obtaining of the concentration of the greenhouse gas carbon dioxide.

Abstract: A method for high-accuracy wavefront measurement based on grating shearing interferometry, which adopts a grating shearing interferometer system comprising an illuminating system, an optical imaging system under test, an object plane diffraction grating plate, an image plane diffraction grating plate, a two-dimensional photoelectric sensor, and a calculation processing unit. The object plane diffraction grating plate and the image plane diffraction grating plate are respectively arranged on the object plane and the image plane of the optical imaging system under test. The shearing phase of 1st-order diffracted beam and ?1st-order diffracted beam is exactly extracted through phase shifting method, and the original wavefront is obtained by carrying out reconstruction algorithm according to a shear ratio of 2s, such that the accuracy of wavefront measurement of the optical imaging system under test is improved, wherein s is the shear ratio of the grating shearing interferometer.

Abstract: A radial servo control device for a super-resolution optical disc includes an excitation light source, a servo light source, an integrated optical path, focusing units, a servo light detecting unit and a drive control unit; the drive control unit presets N detection error reference values with respect to each guide layer trench irradiated by servo light, and controls corresponding positions of the focusing units in N data tracks below each guide layer trench according to a comparison result between a detection result of servo reflected light and the detection error reference values. The device is applicable to a variety of super-resolution optical discs on the basis of stimulated radiation loss microscopy technology, a two-photon absorption technology, and the like, and achieves accurate radial servo control of super-resolution data tracks (<100 nm) without reducing the wavelength of servo light and the width of guide layer trenches.

Abstract: A light intensity fluctuation-insensitive projection objective wave aberration detection device and a detection method thereof, comprising a light source and illumination system, an object plane marking plate, an object plane displacement table, a tested projection objective, an image plane marking plate, a two-dimensional photosensor, an image plane displacement table and a control processing unit; the object plane marking plate and the image plane marking plate are provided with grating marks for shear interference test and marks for light intensity test, the shear interferograms and the light intensity information are simultaneously received through the two-dimensional photosensor, the light intensity fluctuation error corresponding to each phase-shifting interferogram is corrected through the light intensity information, improving the detection precision, reducing the complexity and the cost of the system, and improving the detection speed.

Abstract: A surface defect measuring apparatus and method by microscopic scattering polarization imaging is provided. The apparatus mainly comprises a laser, a first converging lens, a rotary diffuser, a second converging lens, a diaphragm, a third converging lens, a pinhole, a fourth converging lens, a polarizer, a half-wave plate, a polarizing beam splitter, an X-Y translation stage, a sample, a microscope lens, a quarter-wave plate, a micro-polarizer array, a camera and a computer. The micro-polarizer array is adopted to realize real-time microscopic scattering polarization imaging of the surface defects; a polarization-degree image is calculated to improve the sensitivity for detecting the surface defects of the ultra-smooth element, and the effective detection of the surface defects of a high-reflective coating element is also realized, and the requirement for rapid detection of the surface defects of a meter-scale large-aperture ultra-smooth element can be met.

Abstract: A Group VB element doped with a ?-gallium oxide crystalline material, and a preparation method and application thereof. The series doped with the ?—Ga2O3 crystalline material is monoclinic, the space group is C2/m, the resistivity is in the range of 2.0×10?4 to 1×104?·cm, and/or the carrier concentration is in the range of 5×1012 to 7×1020/cm3. The preparation method comprises steps of: mixing M2O5 and Ga2O3 with a purity of 4N or more at molar ratio of (0.000000001-0.01):(0.999999999-0.99); an then performing crystal growth. The present invention can prepare a high-conductivity ?-Ga2O3 crystalline material with n-type conductivity characteristics by conventional processes, providing a basis for applications thereof to electrically powered electronic devices, optoelectronic devices, photocatalysts or conductive substrates.