Laser shock processing (LSP) is a new and efficient type of laser surface treatment technologies. Compared with the traditional surface modification technologies, laser shock processing can form a deeper re-sidual stress layer to the material and make surface grain refinement or even appear nano-crystalline, mean-while significantly improving the fatigue life of the material. When the high-energy laser irradiates at the con-finement layer (black paint, black tape or aluminum foil), the material of the confinement layer is instantaneously melted and gasified to produce a high-temperature and high-pressure plasma. The plasma shock wave is a detonation wave that can be used to calculate the peak pressure of the shock wave by the C-J model. The plas-ma propagates to the interior of the material under the constraint of the confinement layer (water or optical glass). The pressure of the shock wave far exceeds the elastic yield limit of the material. Therefore, the material under-goes elastic-plastic deformation and eventually forms a stable residual stress field and a slight plastic defor-mation. The development of the technology research process is also introduced. On this basis, the development direction of the technology is forecasted. Key

Adaptive optics has played an important role in high resolution telescope. The low order aberrations of the telescope can be completely compensated by adaptive optics, but it causes the loss of the compensation stroke of the deformable mirror. The middle and high order aberrations after compensating of the deformable mirror have some residual aberration, so we need control the residual aberration to ensure high resolution im-aging quality, especially the high order residual aberration that can’t be compensated, which should be strictly controlled in the beginning of the design of the telescope system. This paper analyzes the structure of primary mirror of the telescope optical system, secondary mirror block, secondary mirror support bars block, the primary mirror and secondary mirror alignment, and the static and quasi-static aberration of the optical machining. The influence of these factors on the adaptive optics compensation is analyzed, and the requirements of the aberra-tion control are given. Key

Commercial confocal microscopy usually utilizes two-dimensional galvanometer to scan specimen, the frame rate is limited within 30 f/s, and commercial confocal microscopy is 10 f/s or lower. In order to improve the imaging speed of confocal system, and meet the needs of real-time observation of in vivo imaging, in the high-speed confocal line scanning laser microscopy, the sample is illuminated by one-dimensional scanning la-ser beam. The imaging speed is greatly improved. At the same time, a slit is placed before the linear array CCD to filter out to the non-focused plane stray light and improve the image quality. Experiments show that the optical magnification is 55, horizontal resolution is higher than 2.2 μm, and the frame rate is up to 50 frame per second when the linear CCD scans with 28 kHz horizontal frequency and 512 pixels×2048 pixels image resolution, im-age experiment of plant and animal cells prove that this imaging system could be used in ex vivo or in vivo cell image.

A high-speed, eight-channel pyrometer for precise temperature measurements in the 1500 K to 10000 K temperature range has been designed. It can be used in shock physics experiments to measure temperature of shock loaded sampling. The wavelength and bandwidth of each channel are optimized by analysis and calcula-tion. The semiconductor detectors of Si and InGaAs are used as photoelectric devices, whose bandwidth is 150 MHz and working wavelength covers 400 nm~1700 nm range. By combing the high-transmittance beam-splitters and narrow- bandwidth filters, the peak spectrum transmissivity of each channel can all be higher than 60%. This pyrometer is calibrated by using high temperature blackbody furnace and standard opto-electronic pyrometer. Key

In order to solve the problem of displacement monitoring of health monitoring system in the complex electromagnetic environment, and realize the real-time monitoring of large mechanical and engineering struc-ture health and safety conditions, a novel fiber Bragg grating displacement sensor based on the structure of the cantilever beam is designed. Two fiber gratings with different central wavelengths are symmetrically pasted on the both sides of the cantilever beam. When the free end of the cantilever beam is changed, the two fiber grat-ings are respectively subjected to tension and pressure, which leads to the drift of the gratings center wavelength to the opposite directions. Through demarcating the relationship between the two center wavelength difference and displacement, it is possible to realize the measurement of the displacement. At the same time, the problem of cross sensitivity between temperature and displacement is solved. The sensor adopts draw-wire type dis-placement transmission mode, which makes the sensor installation location and measurement method more flexible. In addition, a smart device used to change the measuring range of the sensor is designed and it is also easy to be assem-bled and disassembled, so the whole sensor can be widely used. The experimental results show that when the range is 60 mm, the average sensitivity of the displacement sensor is 47.7 pm/mm，the correlation coefficient is 0.998, the repeatability error is 2.83% FS and the hysteresis error is 1.02% FS. The displacement sensor is char-acterized by simple structure and adjustable range, which can meet the demands of displacement measurement under different environments.

A microlens with a specific size is fabricated by using melting photoresist, and the microlens can be applied to a shortwave 1 μm ~3 μm infrared detector, which can effectively improve the photoelectric perfor-mance of the detector. Using AZP4620 thick photoresist and UV lithography technology, the lens production in the soft bake, exposure and development, hardening, hot melt and other processes were carried out in-depth and detailed experimental study was done to determine the optimal process parameters. The micro-lens with a crown diameter of (5.5 ± 0.5) μm and a radius of curvature of 3 μm was realized. The lens has good uniformity and consistency to meet the requirements of near infrared detection device.

In order to solve the problem of the rapid detection of aircraft engine in situ cracks, and get the rela-tionship between feature information and detect depth, the laboratory experimental platform is built, laser is used to excite laser ultrasonic signals on a range of aviation aluminum plates with different depth defects, the collect-ed signal is proposed by wavelet de-noising, and the band energy distribution of the reflected echo signal is studied by using wavelet packet. The results show that the energy of reflected echo signal is mainly concentrated in the S80～S87 band. When the depth of defect is 0.2 mm to 0.4 mm, the energy is mainly concentrated in the ad-jacent bands. When the depth of defect is 0.5 mm to 0.7 mm, the energy is mainly concentrated in the two bands. This method provides a way to quantify surface micro-defects by ultrasonic signals, which will lay a foundation for the future analysis of crack depth from band energy. Key

The blades on the plane are one of the most important parts of the engine, in the course of service, due to high temperature, strong vibration and great centrifugal force and so on. The using environment is very bad, so it is easy to produce fatigue cracks in the welding site and the near surface of the root, which will seriously affect the blade of the work intensity and fatigue life, and even the safety of aircraft structure, causing a huge security risk. Therefore, it must be tested. In order to solve the problem of the rapid detection of aircraft engine in situ cracks, and gett the relationship between feature information and detect depth, the laboratory experimental platform was built, laser was used to excite laser ultrasonic signals on a range of aviation aluminum plates with different depth defects, the collected signal was processed by wavelet de-noising, and the band energy distribution of the reflected echo signal was studied by using wavelet packet. The results show that the energy of reflected echo signal is mainly concentrated in the S80～S87 band. When the depth of defect is 0.2 mm to 0.4 mm, the energy is mainly con-centrated in the adjacent bands. When the depth of defect is 0.5 mm to 0.7 mm, the energy is mainly concentrated in the two bands. This method provides a way to quantify surface micro-defects by ultrasonic signals, which will lay a foundation for the future analysis of crack depth from band energy.In order to avoid the interference of other irregular cracks, the cracks of the aviation aluminum parts are used as artificial way for producing. The overall size of the specimen is 200 mm×80 mm×100 mm, the width of the defect is 0.15 mm, the range of the defect depth is 0.2 mm~0.7 mm, step size is 0.1 mm, and the total number of the specimen is six. After the experimental data is proposed, choosing the reflected echo signal for analysis, perform-ing wavelet packet transform, the decomposition layer is 8. The percentage in the S80-S87 band is 89.77%、91.82%、91.41%、90.94%、90.19%、and 87.86%. The result shows that most of the energy is concentrated in the first eight bands. Therefore, the paper selects the first eight bands for analysis.In order to analyze the distribution characteristics of the different depth defect and the band energy, the energy distribution of the first four bands of the defect depth of 0.2 mm to 0.4 mm is plotted in Fig, according to the spec-trum, getting the center frequency were 3.14 MHz, 2.58 MHz, 2.17 MHz. These frequencies are located in the S83, S82, S82 band, respectively, which are the largest energy band, but the energy distribution in the adjacent segment S82 also accounts for a larger proportion. When the depth of the defect increases from 0.2 mm to 0.4 mm, the center frequency decreases gradually, and the sum of the energy of the center frequency band and the adjacent higher en-ergy band increases gradually.

Most of our domestic infrared detector’s photosensitive surface is less than the pixel surface area. A part of the incident light irradiates to the photosensitive area between the dead zone, and this part is not used but reflected and scattered. The microlens array with specific size was fabricated by photoresist fusion method, then a micro-lens array was used to converge to a 1 μm ~3 μm infrared detector, the surface area of the infrared detector can be expanded to reduce noise of the infrared detector and prevent incident light from entering the dead zone. The main process steps include: substrate cleaning, coating and glue, soft baking, exposure and development, baking, hot melt, ion beam etching and so on. The specific process steps: first, in order to obtain the photoresist pattern re-quired for the micromirror curvature, we chose the AZP4620 positive photoresist for the thick film, and the re-fractive index of the photoresist was 1.64. Second, the substrate treatment, removing the substrate surface grease and other impurities to ensure that the substrate and the photoresist had good adhesion. Third, the substrate was coated with a uniform photoresist, and the photoresist was placed under the mask plate which had been set in ad-vance and subjected to UV exposure, the corresponding cylindrical colloid was formed by the development of the image; Fourth, the substrate put into the rapid annealing furnace for hot-melt, the photoresist was heated in the rapid annealing furnace, the surface area of the melted photoresist would shrink to a minimum and the surface energy was the lowest due to the combined action of the surface tension and the substrate adhesion. After the hot melt getting a stable spherical crown microlens must require photoresist cylinder that reduced the amount of gravity is equal to the increase in the amount of potential energy. In the experiment, not any size and the thickness of the cylindrical colloid can form good spherical surface shape after hot melt to meet the design requirements of spherical shape by the photoresist cylinder diameter size, height, and the infiltration degree of glue and basal de-cision. Photoresist as an amorphous polymer is composed of a variety of chemical composition. The melting point of the photoresist is not an accurate temperature, but a temperature range in which the state of the photore-sist exhibits a liquid state. Because of the different types of photoresist, the melting point range is different. Finally, the uniform microlens array was obtained with an ion beam etch machine. By optimizing the temperature and time parameters of each step process, the microlens with a crown diameter of (5.5 ± 0.5) μm and a radius of cur-vature of 3 μm was realized, the microlens had good uniformity and consistency, and the infrared detection was carried out in the 1 μm ~3 μm band device requirements.

Displacement measurement technology is widely used and it is one of the most basic testing techniques. In order to solve the problem of displacement monitoring of health monitoring system in the complex electromagnetic environment, and realize the real-time monitoring of large mechanical and engineering structure health and safety conditions, a novel fiber Bragg grating displacement sensor based on the structure of the cantilever beam is de-signed in this paper. The fiber Bragg grating displacement sensor is mainly composed of cantilever beam, fiber Bragg grating, central transmission shaft, bearing, torsion spring and displacement conversion device. The main body of the sensor is encapsulated inside a box, and a smart displacement conversion device is specially designed outside the box, which is used to adjust the range of the sensor and realize the measurement in wide range. Two fiber gratings with different central wavelengths are symmetrically pasted on the both sides of the cantilever beam. When the free end of the cantilever beam is changed, the two fiber gratings are respectively subjected to tension and pressure, which leads to the drift of the gratings center wavelength to the opposite directions. Through de-marcating the relationship between the two center wavelength difference and displacement, it is possible to realize the measurement of the displacement. At the same time, the influence of the temperature on the wavelength shift can be eliminated by central wavelength difference of the two gratings, and the problem of cross sensitivity be-tween temperature and displacement is also solved. The sensor adopts draw-wire type displacement transmission mode, which makes the sensor installation location and measurement method more flexible. In addition, a smart device used to change the measuring range of the sensor is designed and it is also easy to be assembled and disas-sembled, so the whole sensor can be widely used. The displacement measurement system and temperature meas-urement system are set up to test the overall performance of the displacement sensor. The experimental results show that when the range is 60 mm, the average sensitivity of the displacement sensor is 47.7 pm/mm, the corre-lation coefficient is 0.998, the repeatability error is 2.83% FS and the hysteresis error is 1.02% FS. The tempera-ture coefficients of FBG1 and FBG2 are 25.8 pm/℃ and 28.9 pm/℃, as well as the temperature coefficient of the sensor is -3.1 pm/℃. The structure of the double grating can achieve the effect of temperature compensation, re-duce the temperature coefficient of the displacement sensor, and reduce the influence of the change of the envi-ronmental temperature on the displacement measurement. The displacement sensor is characterized by simple structure and adjustable range, which can meet the demands of displacement measurement under different envi-ronments.

A reliable temperature measurement is a key diagnostic in many industrial and scientific applications. The tem-perature measurement of a sample under shock loading is of special interest. The temperature of interest in shock physics is in the range of 1500 K to 10000 K. The wavelength range of peak blackbody spectral radiance for these temperatures where signal would be maximum is from 280 nm to 1930 nm calculated by the Wien’s displacement law λmax=2897.7(μm·K)/T. However, as limited by the currently applicable detectors, we have developed an eight-channel, high-speed, single-fiber instrument in the spectral range of 400 nm thru 1700 nm in this work. The working wavelength of each channel is selected as 500 nm, 700 nm, 900 nm, 1100 nm, 1250 nm, 1350 nm, 1500 nm and 1600 nm. The radiation from the target in the field of view (FOV) of the system is collected by the optical probe. It passes through the fiber (F1), and then is coupled and collimated by the fiber coupler (FC) and the broadband collimating lens (LL). The collimated beam is spectrally splitted into eight beams by the long-wave-pass beam-splitters (BS1 to BS7) and three total reflective mirrors (M1 to M3) coated with golden film. The eight beams pass through eight bandpass filters (BF1 to BF8), and then they are coupled onto the eight photo detectors (D1 to D8) by independent focusing lenses (L). A laser collimation system composed of laser, fiber (F2) and fiber coupler (FC) is used for the probe alignment before experiment. The temperature from 1500 K to 10000 K is then measured by optimizing the linearity of each channel. The multilayered dichroic beamsplitters and band-pass filters are used to narrow the spectral range of each detector. The current generation of semiconductor detec-tors is capable of high responsivity and high speed (~10 ns rise-time) over the above wavelength range when coupled to appropriate, high-gain transimpedance amplifiers, all at a modest price. The semiconductor detectors of Si and InGaAs are used as photoelectric devices, whose bandwidths are 150 MHz. Their working wavelengths cover 400 nm~1700 nm range. By combining the high-transmittance beam-splitters and narrow-bandwidth filters, the peak spectrum transmissivity of each channel can be higher than 60%. We finished calibration of this pyrom-eter and get the linear constant k(λ) by using high temperature blackbody furnace and standard opto-electronic pyrometer.

A reliable temperature measurement is a key diagnostic in many industrial and scientific applications. The tem-perature measurement of a sample under shock loading is of special interest. The temperature of interest in shock physics is in the range of 1500 K to 10000 K. The wavelength range of peak blackbody spectral radiance for these temperatures where signal would be maximum is from 280 nm to 1930 nm calculated by the Wien’s displacement law λmax=2897.7(μm·K)/T. However, as limited by the currently applicable detectors, we have developed an eight-channel, high-speed, single-fiber instrument in the spectral range of 400 nm thru 1700 nm in this work. The working wavelength of each channel is selected as 500 nm, 700 nm, 900 nm, 1100 nm, 1250 nm, 1350 nm, 1500 nm and 1600 nm. The radiation from the target in the field of view (FOV) of the system is collected by the optical probe. It passes through the fiber (F1), and then is coupled and collimated by the fiber coupler (FC) and the broadband collimating lens (LL). The collimated beam is spectrally splitted into eight beams by the long-wave-pass beam-splitters (BS1 to BS7) and three total reflective mirrors (M1 to M3) coated with golden film. The eight beams pass through eight bandpass filters (BF1 to BF8), and then they are coupled onto the eight photo detectors (D1 to D8) by independent focusing lenses (L). A laser collimation system composed of laser, fiber (F2) and fiber coupler (FC) is used for the probe alignment before experiment. The temperature from 1500 K to 10000 K is then measured by optimizing the linearity of each channel. The multilayered dichroic beamsplitters and band-pass filters are used to narrow the spectral range of each detector. The current generation of semiconductor detec-tors is capable of high responsivity and high speed (~10 ns rise-time) over the above wavelength range when coupled to appropriate, high-gain transimpedance amplifiers, all at a modest price. The semiconductor detectors of Si and InGaAs are used as photoelectric devices, whose bandwidths are 150 MHz. Their working wavelengths cover 400 nm~1700 nm range. By combining the high-transmittance beam-splitters and narrow-bandwidth filters, the peak spectrum transmissivity of each channel can be higher than 60%. We finished calibration of this pyrom-eter and get the linear constant k(λ) by using high temperature blackbody furnace and standard opto-electronic pyrometer.

In traditional commercial confocal image system, detecting light emitted from the light source through a pinhole into a point light, the reflected light from specimen go through the pinhole into the detector. In this case, only the reflected light from the focusing plane could reach the detector. Non-focused light cannot pass through the pinhole and therefore cannot be imaged in the detector. However, traditional confocal imaging system use point by point scanning to image the sample, so the field of view is small (200 μm×200 μm), the imaging speed is slow (10 fps typical), and the image speed is much slower for larger field of view.In order to improve the imaging speed and increase the field of view, the line scanning confocal systems use one-dimensional-focused line beam to scan the sample, and use the slit to filter light strayed from non-focused plane. Non-focused light cannot pass through the slit filter and be imaged by the detector. Compared with the point by point scanning system, the line scanning microscope system can image the sample by only one dimension scanning, which improves the image speed and field of view greatly.The line scanning confocal microscopes uses high speed galvanometer scanning mirror and 28 kHz line array camera to get high resolution (512 pixels×2048 pixels) image, and the frame frequency of the system could reach 50 fps (frame per second), which is much higher than the point scanning confocal microscope. And the higher line frequency the camera has, the higher imaging speed could the system reaches. Theoretical analysis and experi-mental result show that the optical magnification of the line scanning confocal microscope is 55, and the field of view is 713 μm×713 μm. We use resolution test target to find that the system could distinguish at least 288 line pairs in the target, which means that the lateral resolution of the line scanning confocal microscope is higher than 2.2 μm. The axial resolution of the microscope is defined as the FWHM (full width at half maximum) of the de-tected light intensity. The ground glass flat is placed as sample and the axial resolution is about 9 μm in this sys-tem. Finally, images of plants and human cells is got by the confocal line scanning microscope, and cells could clearly distinguish from the images, which proves that the system could be used in cells biological cell imaging.

Negative pressure wave technique is an effective method for pipeline leak detection. However, the low sensitivity and poor locating accuracy seriously limit the applications of negative pressure wave in pipeline leakage detection. In order to obtain more accurate inflection point information of negative pressure wave and improve signal to noise ratio, the response time, static stability and anti-electromagnetic interference of the optical fiber sensor and the traditional electronic pressure sensor are analyzed.In the 102.8 meters pipeline experimental platform, the optical fiber sensor and the electronic sensor are set in pairs, with distance of about 10 cm, to open the leakage valve and compare the response time of both sensors ac-cording to the negative pressure wave signal captured by the sensors. In the constant pressure state, collected pressure data after the signal is stable, recording the real-time pressure change and testing the long-term stability of the two sensors. In order to further verify the reliability of the data, the current output circuit of the electronic sensor is cascaded with 500 Ω resistors, and the voltage of the two ends of the resistor is real-time monitored us-ing the oscilloscope to test the stability of the sensor output current. At the same time, water cycle in the whole pipeline is powered by a water pump, so there is 50 Hz frequency electromagnetic interference in the experimental environment, adjusting the internal pressure of the pipeline. After the pressure is stable, the pressure data of the two sensors are recorded, and comparative analyses to test the anti-electromagnetic interference performance are carried out.Experimental results show that optical fiber sensor takes about 30 ms, and negative pressure wave signal of the leakage is acquired to the pressure signal resumes stable, which is far better than the electronic sensor with the time of 500 ms. In the static stability experiment, the pressure signal output of optical fiber sensor is stable, and the pressure fluctuation range is ± 0.001 MPa, which is far less than the electronic sensor’s ± 0.006 MPa. In the electromagnetic interference experiment, with the influence of the water flow and the vibration of the pipeline, the pressure value of optical fiber sensor has a small fluctuation, and the fluctuation range is about ± 0.01 MPa. As to the electronic sensor, due to the sensitivity to electrical interference, the monitored pressure fluctuation range is ± 0.005 MPa, which is accompanied by pressure mutation point. Comprehensive evaluation analysis shows that the optical fiber sensor has excellent stability and electromagnetic interference resistant performance, and has wide application prospect in the fields of pipeline leakage monitoring, energy and chemical industry.

Negative pressure wave technique is an effective method for pipeline leak detection. However, the low sensitivity and poor locating accuracy seriously limit the applications of negative pressure wave in pipeline leakage detection. In order to obtain more accurate inflection point information of negative pressure wave and improve signal to noise ratio, the response time, static stability and anti-electromagnetic interference of the optical fiber sensor and the traditional electronic pressure sensor are analyzed.In the 102.8 meters pipeline experimental platform, the optical fiber sensor and the electronic sensor are set in pairs, with distance of about 10 cm, to open the leakage valve and compare the response time of both sensors ac-cording to the negative pressure wave signal captured by the sensors. In the constant pressure state, collected pressure data after the signal is stable, recording the real-time pressure change and testing the long-term stability of the two sensors. In order to further verify the reliability of the data, the current output circuit of the electronic sensor is cascaded with 500 Ω resistors, and the voltage of the two ends of the resistor is real-time monitored us-ing the oscilloscope to test the stability of the sensor output current. At the same time, water cycle in the whole pipeline is powered by a water pump, so there is 50 Hz frequency electromagnetic interference in the experimental environment, adjusting the internal pressure of the pipeline. After the pressure is stable, the pressure data of the two sensors are recorded, and comparative analyses to test the anti-electromagnetic interference performance are carried out.Experimental results show that optical fiber sensor takes about 30 ms, and negative pressure wave signal of the leakage is acquired to the pressure signal resumes stable, which is far better than the electronic sensor with the time of 500 ms. In the static stability experiment, the pressure signal output of optical fiber sensor is stable, and the pressure fluctuation range is ± 0.001 MPa, which is far less than the electronic sensor’s ± 0.006 MPa. In the electromagnetic interference experiment, with the influence of the water flow and the vibration of the pipeline, the pressure value of optical fiber sensor has a small fluctuation, and the fluctuation range is about ± 0.01 MPa. As to the electronic sensor, due to the sensitivity to electrical interference, the monitored pressure fluctuation range is ± 0.005 MPa, which is accompanied by pressure mutation point. Comprehensive evaluation analysis shows that the optical fiber sensor has excellent stability and electromagnetic interference resistant performance, and has wide application prospect in the fields of pipeline leakage monitoring, energy and chemical industry.

Phase locking is one of the key issues for fiber laser array applications, like coherent beams combining and fiber laser phased array. These applications can be applied in fiber laser systems like laser radar, target tracking, active illumination, free-space laser communication and direct energy. Phase locking is aimed at stabilizing the wave-front phase at the pupil of each element in the fiber laser array, which is mainly caused by the path length fluctuations between uncommon lengths of fiber. Most existing fiber array systems compensate for the piston dif-ference through measuring the output phase of the array by sampling the outgoing beam using free space optical devices outside the array. To avoid the complex and dumb spatial optical devices, a new technique of phase-locking control in all fiber link based on fiber coupler has been proposed. Laser beams backscattered by the fiber tips of the different outgoing fiber laser beams interfere with each other in the fiber couplers. Meanwhile, the outgoing laser beams interfere with the partial local laser beams in the fiber couplers. These interference results provide metrics for phase-locking control algorithm named stochastic parallel gradient descent (SPGD). Laser beams are then phase-locked on their outgoing fiber tips under such system. Function of the fiber coupler is forming conventional interferometry scheme. Different from existing phase-locking methods based on active phase difference measurement, phase-locking here is achieved through optimization algorithm. The main ad-vantage of such technique is avoidance of high-speed phase modulators and complex phase demodulation. This provides a potential way to realize phase locking control with light and fiber-integrated scheme. Model of such novel phase-locking system for multi-laser-beams is built and steady-state control conditions are discussed. All fiber phase-locking is achieved for two laser beams in our experiment. The two laser beams are collimated and adjusted to overlap and interfere with each other in far field. Interference patterns in far field are collected by high speed camera to judge the control performance. Experimental results show that such technique promotes the fringe visibility of the long-exposure pattern during 10 s from 0.25 in open loop to 0.82 in closed loop, under phase disturb with an amplitude of 4 wavelengths and a frequency of 2 Hz. Fringe visibility of the short exposure pattern rises from 0.65 to 0.98 correspondingly. Experimental results prove that the phase locking method pro-posed here is effective to stabilize the wave-front phase of the fiber laser array.

Phase locking is one of the key issues for fiber laser array applications, like coherent beams combining and fiber laser phased array. These applications can be applied in fiber laser systems like laser radar, target tracking, active illumination, free-space laser communication and direct energy. Phase locking is aimed at stabilizing the wave-front phase at the pupil of each element in the fiber laser array, which is mainly caused by the path length fluctuations between uncommon lengths of fiber. Most existing fiber array systems compensate for the piston dif-ference through measuring the output phase of the array by sampling the outgoing beam using free space optical devices outside the array. To avoid the complex and dumb spatial optical devices, a new technique of phase-locking control in all fiber link based on fiber coupler has been proposed. Laser beams backscattered by the fiber tips of the different outgoing fiber laser beams interfere with each other in the fiber couplers. Meanwhile, the outgoing laser beams interfere with the partial local laser beams in the fiber couplers. These interference results provide metrics for phase-locking control algorithm named stochastic parallel gradient descent (SPGD). Laser beams are then phase-locked on their outgoing fiber tips under such system. Function of the fiber coupler is forming conventional interferometry scheme. Different from existing phase-locking methods based on active phase difference measurement, phase-locking here is achieved through optimization algorithm. The main ad-vantage of such technique is avoidance of high-speed phase modulators and complex phase demodulation. This provides a potential way to realize phase locking control with light and fiber-integrated scheme. Model of such novel phase-locking system for multi-laser-beams is built and steady-state control conditions are discussed. All fiber phase-locking is achieved for two laser beams in our experiment. The two laser beams are collimated and adjusted to overlap and interfere with each other in far field. Interference patterns in far field are collected by high speed camera to judge the control performance. Experimental results show that such technique promotes the fringe visibility of the long-exposure pattern during 10 s from 0.25 in open loop to 0.82 in closed loop, under phase disturb with an amplitude of 4 wavelengths and a frequency of 2 Hz. Fringe visibility of the short exposure pattern rises from 0.65 to 0.98 correspondingly. Experimental results prove that the phase locking method pro-posed here is effective to stabilize the wave-front phase of the fiber laser array.

In the process of high resolution imaging of celestial objects, adaptive optics system plays an important role in the compensation of atmospheric turbulence and the improvement of imaging quality. However, the adaptive optics system is in a certain condition between two extreme situations, which are fully uncompensated and fully com-pensated, and belongs to partially compensated optical system. Adaptive optics can achieve almost full compen-sation for low order aberrations, but the compensation ability for high order aberration is limited. The low order aberrations of the telescope can be completely compensated by adaptive optics, but it causes the loss of the com-pensation stroke of the deformable mirror. The middle and high order aberrations after compensating of the de-formable mirror, which are produced mainly by telescope structures, alignment and processing, have some resid-ual aberration. This residual aberrations result in severe degradation of imaging quality of the telescope. So we need control the residual aberration to ensure high resolution imaging quality, especially the high order residual aberration that can’t be compensated, which should be strictly controlled in the beginning of the design of the tel-escope system.We analyze the influence of the telescope optical structures on adaptive optics compensation, mainly for the 4 meter telescope. First of all, the simulation analysis of adaptive optics system layout of the 4 meter telescope is presented, in order to analyze the residual aberrations with compensated by 4 meter adaptive optical system. The specific analysis of the optical structures on the layout correction capability of our adaptive optical system con-tains the following content: the structure of primary mirror of the telescope optical system, mainly the honey-comb structure, the primary mirror support structure, the primary mirror temperature deformation, secondary mirror block, secondary mirror support bars block, and the static and quasi-static aberration of the optical pro-cessing. The influence of these factors on the adaptive optics compensation is analyzed, so that the requirements of the aberrations control are given.Low order aberrations such as defocus and astigmatism caused by primary and secondary mirror alignment, primary mirror support, and primary mirror thermal deformation, can be completely corrected by adjusting the secondary mirror or using a single deformable mirror which has large compensation stroke. High order aberra-tions out the ability of adaptive optics compensation, such as the aberrations caused by honeycomb structure of primary mirror, can be compensated by data processing. In the process of telescope design and processing, the factors that lead to a large number of high order aberrations should be strictly controlled, and high control re-quirements are put forward.

Superhydrophobic surfaces have attracted extensive interest and research into their fundamentals and potential applications, including self-cleaning, anti-icing, anti-corrosion, reduction of drag, oil/water separation, biomedical devices and microfluidic manipulation. Laser texturing provides a facile and promising method to make superhy-drophobic metallic surfaces. However, immediately after laser texturing, the metallic surface becomes hydrophilic or superhydrophilic. It takes several weeks to months to achieve wettability transition from superhydrophilicity to superhydrophobicity under ambient conditions. This poses a barrier to mass production and industrial appli-cations. Therefore, external stimuli have been applied to change the surface composition and/or the surface mor-phology to influence wettability transition. Among these methods, temperature tuning has attracted special atten-tion due to its advantage of being a simple and controllable process.A nanosecond pulsed fiber laser is employed to fabricate the micro/nanostructures on the as-prepared brass sample surfaces. The surface morphology of the laser textured samples is then characterized by a field-emission scanning electron microscope. A uniform distribution of periodic micro-scale grid patterns on the brass substrate can be clearly observed in Fig. 1, which is beneficial to uniform superhydrophobic properties in all directions with trapped air.After the laser ablation, a post-processing by temperature tuning is carried out to investigate the influence of temperature on wettability behavior of the laser textured brass surfaces. After temperature tuning, the evolution from superhydrophilic to hydrophobic or superhydrophobic state of laser textured surfaces is evaluated by measuring static contact angle (CA) with a CA analyzer using the sessile drop technique. Time taken to reach the CA of 135 ° is 14, 18, 9, 9, 24, 17 and 17 days for temperature tuning at -16 ℃, 25 ℃, 100 ℃, 150 ℃, 200 ℃, 250 ℃ and 300 ℃, respectively. By low-temperature heating (100 ℃~150 ℃), partial deoxidation of the top CuO layer occurs faster, resulting in the formation of hydrophobic Cu2O. It demonstrates that applying low-temperature heating could greatly speed up the rate of wettability transition of brass surfaces subjected to the laser texturing. After 100 ℃ temperature heating, the sample surface achieves superhydrophobicity with the CA of 150.2 ° after 18 days. Furthermore, for the laser textured brass surface after 100 ℃ temperature heating, a contacting experiment is car-ried out. The experimental results indicate the superhydrophobic performance of the laser textured surface and the low adhesive force between the droplet and the surface.

We propose a method for generating high dynamic range (HDR) radiance maps from a single low dynamic range (LDR) image and its camera response function (CRF). Most single-image based HDR image generation methods expand dynamic range only from bright areas which reduces details visible in shaded areas and induces artifacts at the edge of bright areas. This inspires us to exploit an approach expanding dynamic range both from highlight region and shaded region. The proposed method achieves this goal by performing inverse CRF on image intensity to recover the image irradiance which is taken as HDR image. The method first constructs inverse CRF model and computes its optimal solution, and then selects a weighting function and multiplies it by the optimal solution to make the inverse CRF smooth near the maximum and minimum pixel values, and finally conducts the smooth in-verse CRF on the input LDR image to produce HDR image.The proposed algorithm generates HDR image from single LDR image depending on inverse CRF reconstruction. The main steps include: inverse CRF estimation, inverse CRF smoothness, and HDR image generation. For inverse CRF estimation, the approach first models and then estimates inverse CRF based on the database established by Grossberg. The inverse CRF is reconstructed using the edge pixels in the LDR image based on the Grossberg’s DoRF database and EMoR database, and the prior probability is empirically modeled as a Gaussian mixture model. Then, a Bayesian framework is formed by combining the likelihood function with the prior model. Finally, the optimal inverse CRF is obtained by maximizing the posteriori probability (MAP). For inverse CRF smoothness, because the inverse CRF function typically has a steep slope near the minimal and maximal pixels, it is less smooth and non-monotonic near these extremes. To solve this problem, we introduce a weighting function to make the function more smooth and reduce the effect of the pixels near the minimal and maximal in HDR image construction. The considerable choices of weighting function are rectangular function, triangular function and Gaussian function. For HDR image generation, we can easily conduct the inverse CRF on the input LDR image to generate HDR image.Unlike most existing methods, the proposed method expands image from both high and low luminance regions. Thus, the algorithm can avoid the artifacts and detail loss in dark area which results from extending image only from bright region. Extensive experimental results show that the approach induces less contrast distortion and produces high visual quality HDR image. The significance and novelty of the method include the smoothness function used in the estimation of inverse CRF and the utilization of the inverse CRF in HDR image generation. These novelties realize expanding image both from bright and dark regions while guarantee the quality of generat-ed HDR image.

The concept of “laser” was proposed at the beginning of 20th century. Since then, laser research had always been a popular research area. Laser is widely applied because of its characteristics, such as good direction, high bright-ness, and good color. Laser processing technology is one of the most promising areas for laser applications. Laser shock processing (LSP) is a new and efficient type of laser surface treatment technologies. Modern society makes higher requirements of the service to mechanical parts, and mechanical properties of parts are needed to improve to meet the use. As a typical laser surface treatment technology, LSP can achieve a greater increase of the perfor-mance, compared with other traditional surface treatment technologies. LSP strengthening process is similar to that of shot peening, except that the mechanical effect of laser is used instead of the impact of the projectile. The impact pressure and the influence of depth on the surface of the material are larger. It also has a smaller change to the surface topography of parts. LSP can bring a deeper residual stress layer to the material and make surface grain refinement or even appear nano-crystalline, meanwhile significantly improving the fatigue life of the material. The LSP utilizes the mechanical effect of the laser rather than the thermal effect. The high-energy laser irradiates the material of the confinement layer (usually is black paint, black tape or aluminum foil), and the material of the confinement layer is instantaneously melted and gasified to produce high-temperature and high-pressure plasma. The plasma continues to absorb laser energy and expands to form a shock wave. The plasma shock wave can be seen as a detonation wave of a physical property, and C-J model is used to calculate and predict the variation of the peak pressure of the plasma shock wave. The plasma propagates to the interior of the material under the con-straint of the confinement layer (usually is water or optical glass). The pressure of the shock wave far exceeds the elastic yield limit of the material. Therefore, the material undergoes elastic-plastic deformation and eventually forms a stable residual stress field and a slight plastic deformation. The research and development of LSP are in-troduced, including the key of this technology: the selection and perfection process of absorbing and protective layer. The development direction of the technology is also forecasted.

Developments in miniaturized microscopes have ena-bled visualization of brain activities and structural dy-namics in animals engaging in self-determined behav-iors. However, it remains a challenge to resolve activity at single dendritic spines in freely behaving animals. Research teams from Peking University and Institute of Basic Medical Sciences, CAMS successfully developed a fast high-resolution, miniaturized two-photon micro-scope (FHIRM-TPM), and recorded images of neuronal activities at the level of spines in mice experiencing vigorous body movements.

The spin Hall effect of light (SHEL) refers to the phe-nomena of beam splitting for circularly polarized light at some specific conditions, which has promising ap-plications in nanometric measuring, imaging and sens-ing. In general, the SHEL is very weak. Although the intensity can be increased by using resonant enhance-ment, the response bandwidth is limited. Recently, re-searchers from the State Key Laboratory of Optical Technologies on Nano-Fabrication and Micro-Enginee-ring, Institute of Optics and Electronics, CAS have demonstrated that single nanostructures with 2 μm dimension can generate broadband strong SHEL.

Flexible UV image sensors using flexible electronic technology and ultraviolet (UV) sensor technology, can be applied in much wider range applications in crime investigation, oil spill detecting, fire monitoring, and electrical power line inspection. However, because of the low signal intensity of UV radiation in many practi-cal applications, high-performance flexible UV photo-detectors are critical to realize flexible UV imaging.