Dispersive waves of mid-infrared band generated when the ultrashort pulse is launched into hollow-core Kagome photonic crystal fiber filled with Krypton gas are numerically investigated with the unidirectional pulse propagation equation. Two types of input pulses are studied, including a Gaussian pump centered at 1.4 μm and a near-saw-tooth-shaped two-color pulse centered at 1.4 μm added with its second harmonic. Multiple dispersive waves are observed under the two situations which are in agreement with the phase-matching conditions. In order to optimize dispersive waves, the near-saw-tooth-shaped pulse is used as the pump pulse. The second ionization of Krypton gas filled in fiber is caused by pump pulse compression, so that the earlier-generated dispersive waves are converted to new ones at longer wavelengths. This observation is legitimately explained by the plasma corrected phase-matching condition. The mid-infrared ultrashort pulse generation and the dispersive wave theory are discussed.

Synaptic plasticity provides the basis for learning mechanism in neural network. Anti-spike-timing-dependent plasticity (anti-STDP) learning mechanism is implemented by the nonlinear polarization rotation (NPR) and cross-gain modulation (XGM) based on single semiconductor optical amplifier (SOA). By adjusting the drive current of SOA, the weight and height of long-term potentiation (LTP) and long-term depression (LTD) windows can be adjusted to better mimic the neural network. The anti-STDP learning curves measured by the experiment closely resemble the learning curves measured by the biological system. Using the proposed anti-STDP optical circuit, the time window of anti-STDP learning curves is about several hundred picoseconds, which is 108 times faster than the speed of STDP learning mechanism in human brain. Since the proposed anti-STDP optical circuit is simple, and SOA can be integrated with some other devices easily, it can be used to realize large-scale and ultrafast neuromorphic computing systems.

The asymmetry of gain and time delay in two input paths of the balanced detector will affect the performance of the optical analog-to-digital conversion (PADC) system based on balanced detection. A mathematical model of the PADC system based on balanced detection is built. The relationship between the effective number of bits (ENOB) of the system and the asymmetry of gain and time delay in two input paths of the balanced detector is given. The effect of asymmetry of gain and time delay on ENOB of the system is analyzed by simulation, and corresponding confirmatory experiments are carried out. The results show that ENOB of the system decreases with the increase of relative gain and relative time delay in two input paths under the same modulation depth. When the gain and the time delay in two input paths of the balanced detector are exactly the same, ENOB of the system decreases with the increase of modulation depth. When the gain and the time delay in two input paths of the balanced detector are different, ENOB of the system increases at first with the increase of modulation depth and then decreases.

In order to develop a fiber laser simulation software, which is domestic, interface friendly, easy to use, and instructive in research and industry design, the development and the research for fiber laser simulation software are carried out. Based on the theory study about fiber laser, we develop a software named See Fiber Laser which can be used to the simulation of Yb3+ doped high power fiber laser, and a fiber laser tool collection named SFTool which can be used to calculate the related parameters in fiber laser is developed. Some parts of theory models, basic function and sample calculate examples of the software are introduced. The study may make the research and the design of fiber laser easier.

In order to increase light intensity on the target plane, laser beam array target shooting is usually used in high power laser driver divices, in which 2×2 beam array is widely used at present. The lenses adopted in beam array focusing system lens include off-axis lens and non-off-axis lens. The excellent quality of focal spot can be obtained under ideal conditions when we use the beam array focus system with non-off-axis wedged lenses. The optical propagation model of 2×2 beam array focus system is built, and the influences of various errors on its focal spots during the process of actual installation and adjusting are simulated and investigated. Results show that the mirror angle and the lens translation have great influence on the focal spots quality of the system, and the two components should be precisely adjusted. The influences of mounting angle and focal length error of the lens on the system focal spots quality are relatively little, and it is easy to be satisfied at the present conditions. The researcher′s understanding about multi-beam coherent combination scheme can be improved by this study, and it has a certain guiding significance for the installation and adjustment of practical systems.

The polarization-maintaining capacities of the backscattered linearly and circularly polarized lights in the scattering media composed of particles with different sizes are analyzed with the Monte Carlo simulation method. The comparative research of the micro-change in polarization states between the linearly and the circularly polarized lights in the process of every scattering event is performed by using the Rayleigh and Mie scattering theories. The results show that the polarization-maintaining capacity depends on the polarization state of incident lights and the size of the particles. As for the Rayleigh-scattering particles, the linearly polarized light has a stronger polarization-maintaining capacity. While as for the Mie-scattering particles, the circularly polarized light has a stronger polarization-maintaining capacity.

A flat-panel display backlight module based on blue laser diode is designed, which is composed of light guide module and light guide plate (LGP). The scheme of keeping apart the light guide module and LGP is used in the process of designing optimization. A light guide module whose horizontal part distributes regularly, vertical part distributes unanimously in the transmission process and LGP network with uniform output light distribution are designed. The LGP sample is produced by adopting the method of laser dotting. Theoretical simulation shows that the intensity of illumination uniformity can reach 89.02%, and the average value of corner can reach 102.74%, for the whole module. And experiment measurement shows that the intensity of illumination uniformity can reach 79.61%, the average value of corner can reach 100.10%. The structure of this backlight module is simple, and it can offer back lighting for the liquid crystal display.

In order to increase the exposure contrast of the holographic grating exposure system, and depress the exposure interference fringe drifts caused by the environmental changes, a method of interference fringe locking by grating-shifting is proposed. The beam splitter grating is used to split the beam from laser source and adjust the phase of the interference fringe. The phase changes of the interference fringe are measured indirectly by Moire fringe. The best detection locations of the two photoelectric detectors are given. The parameters design method of the beam splitter grating is presented by combining the function of splitting beam and regulating phase. The controller is designed aiming at the characteristic of the grating exposure. The phase-regulating performances of the beam splitter grating and the piezomirror are contrasted theoretically. The experiment results illustrate that the low-frequency drifts of the interference fringe are depressed at a sample frequency of 500 Hz. The value of the phase locking is below 0.13 rad (3σ), namely the fringe drift is below ±0.021 period. The exposure interference fringe can be timely and effectively locked by this method, and the exposure contrast is improved. The tilt of the beam splitter grating has little effect on fringe′s period. Besides, the phase regulating performance is only relevant to the parameters of the beam splitter grating, which is convenient to the design of the optical layout.

The frequency domain distribution of amplified pulse modulated by the acousto-optic programmable dispersive filter is measured on the 200 TW laser system in Peking University. A spectral modulation function related to the pulse central wavelength and spectral bandwidth is established to fit the measured spectral data. The function is simple and suitable for different laser systems. Based on the numerical simulation of the amplifier output pulse′s spectra after the seed pulse modulation, the time-domain characteristics of the ordinary seed pulse and the spectrum modulated pulse through the amplifier are compared. The effects of spectral modulation on the peak power of the final output pulse are discussed. The result shows that the spectral modulation can lead to the generation of sidelobes and reduce the effective energy and femtosecond contrast of the system output pulse. When the output pulse has a flat-top spectrum, its effective peak power is the largest.

A high power all-fiber (2+1)×1 side-pumped combiner based on tapered-fused method is developed. The theoretical model of the combiner is set up through simulation software, and the coupling efficiency of combiner is calculated. A side-pumped combiner is fabricated. The coupling efficiencies are 98.2% and 96.3% for two pump arms respectively at the pump power of 600 W, and the insertion loss of signal light is about 0.11 dB. The combiner is applied to construct a kilowatt-class fiber laser amplifier. The output power is 1.426 kW at 1080 nm, when the power of bidirectional pumping light reaches 1.8 kW.

In order to solve the existing problems in the measurement and control system of combustion driven deuterium fluoride (DF) chemical lasers, such as the large system volume and complex wiring, an embedded intelligent measurement and control system is designed based on the analysis of the basic functional requirements and operating characteristics of chemical laser measurement and control system powered by a battery pack and using the PIC microcontrollers as the hardware device. The system can be controlled by a PC upper-computer and an Android hand-held upper-computer, which measurement-control instructions and data can be transmitted by the radio frequency wireless or 485 data bus. The intelligent measurement and control system has the functions of flow field data acquisition, supply control of different fuels according to the injection timing sequence, closed-loop control of fuels′ flow rates, and so on. The test results based on the function board show that this embedded intelligent measurement and control system has not only smaller volume, less wiring and lighter weight, but also good expansibility, strong anti-interference ability and reliable data security, which shows a good application prospect, and at the same time, lays a solid foundation for the compactness of the measurement and control system of chemical lasers.

A picosecond fiber laser system based on master oscillator power amplifier (MOPA) is proposed. A passive mode-locked fiber laser with a semiconductor saturable absorber mirror (SESAM) which is with repetition rate of 29.87 MHz is used as the seed source. The repetition rate can be reduced to 574 kHz when a pre-amplifier system is combined with an acousto-optic modulator (AOM). The MOPA structure is based on rod-type photonic crystal fiber (PCF). The pulse with pulse width of 30 ps can be amplified based on properties of large mode field and high gain of PCF, and the spectral expanding caused by the self-phase modulation is effectively suppressed. Results show that the spectral linewidth of 5 dB is proportional to the peak-power of optical pulse of the proposed system (the beam quality factor M2 is 1.01 at the output power of 20 W). The peak-power of the picosecond pulse is 3.4 MW, which is near the diffraction limit. The picosecond pulse with the highest average output power of 21.86 W, pulse width of 11.1 ps, center wavelength of 1030.74 nm and linewidth of 1.75 nm at 5 dB can be obtained.

The purely chemical combustion-driven HBr chemical laser has been studied using D2 as fuel and NF3 as oxidant. The pumping reaction is H+Br2→HBr(v≤6,J)+Br. Hydrogen and fluorine atoms are produced by the reaction of F+H2→HF+H and burning D2/NF3 mixtures, respectively. And a supersonic flow system provides conditions of low temperature, low pressure and fast flowing to satisfy the need of laser extraction. The stable laser output at P2(4)、P2(5)、P3(5) and P3(6) with the maximum output power of 14.3 W is obtained, when we extract energy from the stable cavity consisted of a totally reflection mirror and a partially reflection mirror (98%).

A kind of all-solid-state single-longitudinal-mode Nd∶YVO4 pulse laser based on electro-optical cavity-dumping technology is designed and fabricated. The thermal depolarization originated from the nonuniform pump and laser absorption of the two RTP crystals is reduced via precise temperature control of the pockels cell, and the polarization extinction ratio of the pockels cell is consequently improved. By optimizing the fall time of the pockels cell driver, the problems such as pulse width broadening and power dropping due to the too long time of falling edge are all overcome. At the pump duty cycle of 50%, the incident peak pump power of 16.9 W and the repetition rate of 200 Hz, the single-longitudinal-mode pulse laser with pulse width of 2.85 ns, peak power of 1 MW is obtained. The measured peak power fluctuation of output pulse is less than ±1.8% during a given time of 50 ms, and the time jitter of pulse rising edge is less than ±0.2 ns during 1300 shots.

The thermal effect of a new large aperture N41 Nd∶glass slab which is applied to inertial confinement fusion (ICF) laser drivers is investigated systematically under the condition of high gain. The experimental results show that the peak-valley value of thermal induced wavefront distortion of two slabs with two pass within the diameter range of 385 mm×385 mm is about 0.84λ (λ=1053 nm) when the average small signal net gain coefficient reaches 0.0525 cm-1, which is in the revise extension of deformable mirror. Following the present cooling schemes, the recovery time of residual wavefront distortion is about 2.5 h, which is satisfied the designed requirement of launching once every 4 h. A minuteness wavefront distortion induced by thermal gas convention exists in the system after launching 7 h. Experimental results are consistent with numerical calculation results. The study provides an experimental reference for the design of the next generation slab amplification system in ICF laser drivers.

In order to obtain femtosecond laser pulses with high repetition rate, a burst operation mode is introduced into femtosecond thin-disk regenerative amplification system. The cavity length of the regenerative amplifier is designed as 9.3 m, so that the laser pulse which is close to the diffraction limit can be generated. The repetition rate of the laser pulse is 5 times of the electro-optic modulation frequency. Under the condition that the electro-optic modulation frequency is 5 kHz and the absorbed pump power is 98 W, hyperbolic secant pulses with maximum output power of 10.7 W, spectrum full-width-half-maximum (FWHM) of 1.18 nm, pulse width of 777 fs are obtained. The optical-optical conversion efficiency of the regenerative amplifier increases with the increasing of the electro-optic modulation frequency, and the optical-optical conversion efficiency increases from 12.4% at 0.5 kHz to 25.3% at 5 kHz. The laser output stability improves in the range of 18-20 ℃ with the decreasing of chiller temperature, and the output power root-mean-square of the laser system changes from 0.93% at 20 ℃ to 0.52% at 18 ℃. These results have great values for designing the stable femtosecond laser system with high repetition rate and high power.

For the laser frequency stabilization system which uses rubidium saturated absorption spectroscopy as the laser frequency reference, the loop bandwidth is one of the important facts which influence the laser output frequency noise. The main factors which limit the loop bandwidth of the laser frequency stabilization system are analyzed. Then, the radio frequency modulation signal is used to directly modulate the high speed current modulation port of the commercial external cavity diode laser, and the loop bandwidth of the laser frequency stabilization system is expanded. According to the analysis of the frequency stabilization loop, the feedback circuit is set up to realize the laser frequency stabilization. After analyzing the error signal of stabilized laser by low frequency spectrum analyzer, it is found that the frequency noise suppression can be improved to be larger than 20 dB at the Fourier frequency of 5 kHz. The beat frequency is conduct between laser from stabilized frequency laser and femtosecond optical frequency comb locked on ultra-stable oven controlled crystal oscillator, and the frequency noise of stabilized laser is also measured. The results are consistent with the analyzing results of the error signal. The frequency noise is suppressed when we expand the bandwidth, and the short-term frequency stability of the stabilized frequency laser is improved. Finally, the frequency stability of stabilized frequency laser relative to OCXO referenced femtosecond optical frequency comb is measured. It can reach to 4.52×10-12 at averaging time of 1 s and reach to 1.65×10-12 at averaging time of 20 s.

The time-delay characteristic concealment and the bandwidth expanding of the chaotic output of mutually coupled vertical-cavity surface-emitting lasers (VCSELs) without feedback can′t be achieved simultaneously, so an external optical feedback is added to one of the lasers of mutually coupled VCSELs without feedback. The time-delay characteristic and the bandwidth of the chaotic output from the single-ended feedback and mutually coupled VCSELs are numerically studied. Results show that feedback intensity, frequency detuning and mutually coupled intensity have effects on the time-delay characteristic and the bandwidth of the single-ended feedback and mutually coupled VCSELs. The laser with feedback can′t obtain the time-delay characteristic concealment and the bandwidth expanding simultaneously， but the laser without feedback can obtain the time-delay characteristic concealment and the bandwidth expanding simultaneously in the proper mutually coupled intensity and frequency detuning. Changing the feedback intensity does not effect the quality of the time-delay characteristic concealment and the width of the bandwidth, but can effect the position of the frequency detuning when the time-delay characteristic concealment and the bandwidth expanding are achieved simultaneously. The position of the frequency detuning region moves to the negative frequency detuning region when the feedback intensity increases.

An all polarization maintaining mode-locked fiber laser which is based on bias phase shift nonlinear loop mirror is proposed. An all polarization maintaining mode-locked oscillator system is set up. The system generates pulses with average power of 2.4 W, repetition rate of 20.3 MHz and pulse width of 142 fs by three stages Yb-doped fiber amplification. Since the oscillator adopts all polarization maintaining fiber structure, the mode locking is environmentally stable.

A path planning method for curved surface parts based on the process characteristics of laser cladding is proposed. The point cloud data of the cladding curved-surface are obtained by the 3D scanner and the point set on the cladding path is obtained by the point cloud slicing method. The equal bow height is utilized to make the trajectory point set sparse and the non-uniform rational B-splines (NURBS)curved-surface is fitted to obtain the normal vector of the processing point, and the motion trajectory point of the nozzle is obtained by skewing a certain distance along the direction of this vector. Through the cladding experiment and the quantitative analysis of the experimental sample, it is concluded that the quality of the cladding layer on the curved surface is good, which verifies the reliability and practicability of the proposed method and provides certain reference for the cladding and remanufacturing of other curved-surface parts.

Based on the actual weld shape from stainless steel sheets with non-penetration CO2 laser lap welding and fiber laser lap welding, by taking the Gaussian-plane+cylinder-body composite heat source model, the obtained heat source proportionality coefficients are 0.85 and 0.70, respectively. By correctly setting the other four parameters for describing heat source, including the radius and the depth of Gaussian heat source, and the radius and the depth of cylinder heat source, the change laws of weld shape characterization parameters (surface seam width, middle weld width and weld penetration) of lap welds can be obtained under different welding powers and welding speeds. The simulation results are well consistent with the experimental results.

The austenitic stainless steel is welded with the fiber laser and coaxial protection method. The optical signals during the welding process are collected by the laser welding and synchronously monitoring system, which is combined with the shape of plume to study the influence laws of different welding conditions on the weld formation and optical signal intensity. The results show that the optical signal intensity gradually increases with the increase of laser power. When the defocusing amount changes from -6 mm to 6 mm, the optical signal intensity decreases first and then increases. The optical signal change can reflect the change of weld penetration, which can be used to detect the weld defects caused by the change of the lap gap and the weld position. The exact location of the area with the abnormal welding quality can be judged by analyzing P signal data. The optical signal intensity is positively related to the plume volume during the welding process.

The surface of Ti/FTO composite films prepared with the direct current magnetron sputtering method is irradiated by a nanosecond pulsed laser with a wavelength of 532 nm. The effects of laser energy density on surface morphology, crystal structure, optical and electrical properties of the films are studied. The results show that the irradiation of films with appropriate laser energy density has the annealing effect on film surfaces, which on the one hand promotes film grain growth and eliminates partial crystal defects, and on the other hand, gives rise to the transformation of Ti layer to TiO2 layer via oxidation, and finally improves the overall photoelectric property of the films.

In order to study the influence of side assist gas on the microstructure and the corrosion resistance of welds of austenitic stainless steels in the process of fiber laser welding, a fluid model of side assist gas and metal vapor is established. The influences of different kinds of side assist gases and their flow rates on the metal vapor temperature field and velocity vector are analyzed, and a method to increase the nitrogen content in the weld metals by means of side assist gas is proposed. The experimental results show that, on the premise of keeping the weld formation unaffected, the proposed method can effectively improve the nitrogen content in the upper layer of weld metals, restrain the ratio of ferrite in the weld metals, and enhance the pitting corrosion resistance of the austenitic stainless steel.

Based on Helmholtz-Kirchhoff diffraction integral theorem, the relationship among micro-structure parameters, incident light parameters and transmission light parameters of achromatic uniform light thin film are theoretically derived. The influences of micro-structure parameters on transmission light amplitude distribution and scattering angle are analyzed. When light beam passes through the achromatic uniform light thin film, the scattering light spot has many advantages such as uniform light intensity distribution, achromatism, controllable scattering angles and wave shape. The thin film with the maximum depth of 5 μm and scattering angle of 8°×7.5° is fabricated. The error of measured scattering angle and the theoretical angle is within ±0.5°. The designed thin films can be used in illumination, LCD backlight display, projection system as well as other applications.

The traditional spectral analysis methods of processing spinning satellites laser ranging data have the disadvantages of large computational cost and long processing time. A new satellites laser ranging (SLR) data processing algorithm based on fast Lomb-Scargle algorithm is proposed to solve these problems. Firstly, empirical mode decomposition method is used to adaptively remove the low frequency trend term in the O-C residuals of SLR data, which represents the satellite orbital motion. The preprocessed SLR data is then processed for spectral analysis with fast Lomb-Scargle algorithm to get its periodogram and thus analyze the spinning rate of satellites. Processing the kilohertz SLR data of satellite Ajisai from Graz station of Austria, we can get that the spinning rate of satellite Ajisai during May 2010 is about 0.472 Hz. Further data processing of four passes also have been done by proposed fast algorithm. Results show that the computational cost of spectral analysis is reduced by roughly two orders of magnitude and the processing time is greatly saved by using the fast algorithm. It provides a new way to process large amount of SLR data of spinning satellite fast and efficiently.

In this paper, a pulse temporal profile measurement scheme based on self-focusing lens coupling of single-mode optical fiber for small broadband frequency modulation pulse is introduced. Theoretical analysis and experimental results show that sampling energy with self-focusing lens coupling fiber decreases with the increase of the angle between lens and beam, but spectrum coupling efficiency of different orders is the same at the same angle. It means that the process of sampling will not introduce additional frequency modulation leading to amplitude modulation (FM-AM) effect. When the coupling efficiency drops in a half, the allowable drift angle of beam is 1 mrad. The technique scheme has advantages such as convenient to integrating, low cost and resistant to beam disturbance and electromagnetic interference. Besides, the sampling area has been expanded through the self-focusing lens that effectively improves the sampling energy and suppresses the adverse impact of beam cross section energy ups and downs on the measurement system. The technical scheme provides a certain theoretical and experimental basis for the improvement research of high power laser facility temporal profile measurement technology.

Multilayer dielectric diffraction grating is the most important optical element in spectral beam combining system. The surface distortion of grating under high power laser irradiation will change its diffraction characteristic, which will influence the beam quality and diffraction efficiency of the combining system. We establish an experimental setup of Twyman-Green interferometer to measure the interference fringes on the diffraction grating surface, under the high power laser irradiation. Based on the image processing and Zernike polynomial fitting method, the grating surface profile is reconstructed. With the high power laser heating the grating and another laser measuring the beam quality and diffraction efficiency degradation, the results show that the grating surface deformation distribution conforms to Gaussian model, when the irradiance power density is 3 kW/cm2, the maximum distortion is evaluated to 127 nm, which leads to the diffraction beam quality factor M2 degradation. The degradation is mainly due to the increase of angle divergence after diffraction. The change of diffraction efficiency is less than 1.8%, which is basically unchanged.

In order to realize high precision comparison between remote optical clocks, the two-way optical phase comparison scheme proposed by the Calosso group in Italy is extended, and a two-way optical phase comparison method based on local measurement is proposed. Two optical signals which come from the same laser source are injected from two ends of the same optical fiber. One signal transmits to the far end through the optical fiber and then returns to the local end by reflection. The other signal transmits from the far end to the local end through the optical fiber. In this way, the two signals are beaten at the local end with the reference light to obtain the phases of the two beat signals. In this case, the common-mode phase noise induced by fiber links can be eliminated without the active fiber phase noise compensation. The most important advantage is that the acquisition and the processing for beat frequency signal can be done at the local end without adding extra time synchronous signal to ensure the synchronization of beat frequency signal acquisition, which simplifies the experimental system. The ultimate phase noise performance of the scheme is calculated, and a demonstration system based on 60 km spool fiber is established. The frequency instability are 1.45 × 10-16 for 1 s and 1.51 × 10-19 for 1000 s. The scheme is expected to be used for more reliable high precision frequency comparison among remote optical clocks and other advanced atomic clocks.

A method of stripe gray-scale asymmetry adjustment for strip center extraction is proposed to solve the problem that stripe gray-scale asymmetric distribution degrades the accuracy of stripe center extraction in the structured light measurement. Firstly, the exponentiation of initial gray-scale is obtained. The initial gray-scale is subtracted from exponential calculation result, and the subtraction result is gray-compensated. Then, the gray-scale after compensation is used to iterate until the iteration termination conditions are satisfied. Moreover, the factors that affect the asymmetry of stripe gray-scale distribution are analyzed, and the evaluation parameter of the stripe gray-scale distribution is put forward. Experiments are conducted to verify the proposed method. The results show that the algorithm can effectively adjust the stripe gray-scale according to the initial gray-scale distribution. The iteration result highlights the gray information around the maximum value, reduces the impact of gray-scale asymmetric distribution on stripe center extraction, and improves the accuracy of stripe center extraction. Based on these results, the validity and reliability of this method are verified.

To solve problems such as low recognition rate of abnormal cross section and inability to rule out special structural effects, a method based on one-class support vector machine (OCSVM) is proposed to detect coronary lesion. By using coronary cross section resampling and feature selection based on maximum mutual information, the method achieves a relatively high recognition rate. At first, the coronary cross section is resampled based on gradient flux using cubic spline interpolation, and multi-scale feature vector is constructed for every coronary cross section. Then, a maximum mutual information method combined with redundancy removal is adopted to select target features. Finally, selected features are used to train OCSVM model to complete coronary lesion detection. The experiment results in 1128 cross section data show that the maximal recognition rate of the proposed method of health cross section reaches 53.5%, which is much higher than that of support vector machine (SVM) algorithm (learning only from positive and unlabeled data) of 19.6%, with complete recognition of abnormal cross section. Meanwhile, the health cross section recognition rate by 30 features rises from 21.7% to 53.2% owing to the resampling of the cross section.

One method which combines the triangulation and the function fitting based on 3D point cloud depth information is proposed. The extraction model of surface damage features in high speed sliding electric contact components is built. The 3D feature data in the damaged area are divided into triangulation and the surface damage volume and mass of the components are calculated. The experimental results show that the accuracy in computation of the proposed algorithm can reach 97.3%.

A novel hybrid type double ribbed surface plasmon waveguide structure is designed, and transmission characteristics at the work wavelength of 1550 nm are simulated and optimized based on the finite element method. The electric field distribution, transmission loss, normalized mode field area, quality factor and gain coefficient of the designed structure are studied. The results show that through the optimal parameter design, the effective mode field area is up to 1.5×10-4λ2, the quality factor is 135, the gain factor is 1286 cm-1, and the loss is small. Compared with the rectangular metal mixed ridge waveguide structure, the designed structure has better light field limited ability and can get better waveguide transmission effect. The designed waveguide structure is an important way to solve photoelectric technology with high speed, miniaturization and integration in the future.

Ethylene (C2H4) is a common chemical material in the petroleum and chemical industry. It is explosive and often used as identifier for coal spontaneous combustion. An inexpensive photoacoustic spectrometry based on near infrared tunable diode laser is developed to detect the ethylene with low concentration. By analyzing the near-infrared absorption line of ethylene, we choose absorption line of ethylene at 1620.44 nm as measuring object. By combining wavelength modulation absorption technique, resonant frequency of photoacoustic cell is used as modulation frequency, and the second harmonic signal of absorption line is used to realize inversion of ethylene gas concentration. The results show that the measurement accuracy of ethylene by the system is 0.688%. The detection limit of the system is up to be about 1.16×10-5. A continuous measurement for a gas sample in half an hour shows the stability of the system. All the results represent the application value of the system for trace detection of ethylene.

To achieve the wavelength repeatability ±0.05 nm of the infrared double grating spectrometer, the wavelength scanning mechanism of the spectrometer is designed and the error source that influences the wavelength repeatability is analyzed. According to the structure characteristics and indicator requirements of the spectrometer, the sine mechanism based on lead screw and rocker is designed as the wavelength scanning mechanism. On the basis of concave grating scanning principle, formula from optical parameters to mechanism parameters is derived and the influences of each error source on the wavelength scanning mechanism are analyzed. The analysis results show that the repeatability of the spectrometer in the range of 760~2200 nm should be better than ±0.05 nm when the repeated positioning accuracy of the lead screw is ±1.2 μm. Infrared double grating spectrometer prototype is designed, and experimentally verified. Using mercury lamp as light source, the wavelength repeatability of the wavelength scanning mechanism at the characteristic wavelength is calculated after scanning each characteristic wavelength for 7 times. The experimental results show that the wavelength repeatability of the spectrometer is in the range of -0.038~0.041 nm, and the wavelength scanning mechanism can meet the requirements of the application.

A new discrimination algorithm of Raman spectral peaks is proposed. With Voigt function as the fitting function, the spectral peaks obtained after the ridge peak detection based on the wavelet transformation are fitted. The similarity of spectral peaks before and after fitting is taken as the basis for discrimination of spectral peaks. The Raman signal with amplitude comparable to that of noise is effectively discriminated. Compared with those of the existing two discrimination methods of spectral peaks, the true positive rate of the proposed method improves by 60% when the false data rate is 5% and the false data rate of the proposed method decreases by 10% when the true positive rate is higher than 90%.