By means of simulated annealing genetic algorithm, frequency-response characteristics of nonuniform-delay-time microwave photon filter with full/non positive coefficients are analyzed. And the window-function method is applied at the same time. Simulation results show that the more taps lead to better performance at full-positive symmetric coefficient filter. In the case of low-pass filter, full-positive coefficients limit largely factor on the span of transfer function, the characteristics improvement of non full-positive coefficients filter is obvious. At the same cut-off frequency, the optimal performance of simulated annealing genetic algorithm is slightly better than that of the window-function method. Once limiting the cut-off frequency of pass-band and stop-band, and relaxing the requirements of the transition zone, the advantages of simulated annealing genetic algorithm are much more obvious.

With the rapid development of quantum cryptography, infrared single-photon detection becomes the key technology in this research field. A high-speed InGaAs/InP avalanche photodiode (APD) is presented based on single-photon detector with a 1.25 GHz gating frequency, using the technique of sine wave gating and filtering. When the detection efficiency is 10.3%, dark count probability per gate is 1.3×10-6 and the afterpulse probability per nanosecond is 5.6×10-5. This kind of detector can significantly enhance the performance of quantum cryptosystem in terms of secret key rate and transmission distance, which paves the way towards the practical applications of the next generation quantum cryptography.

Effects of 5-aminolevulinic acid-mediated photodynamic therapy (ALA-PDT) with low energy on intracranial angiogenesis and glioma growth are evaluated. Twenty seven nude mice are received low energy of ALA-PDT (ALA: 300 mg/kg, dose: 10 J/cm2) on the right side of the cerebral cortex. After 1、5、10 days, angiogenesis is evaluated by 2 and 3 dimensional vessel images, and expressions of VEGF and hypoxia-inducible factor-1α (HIF-1α) by western blot. Other 12 nude mice are divided into control and ALA-PDT (10 J/cm2) pretreated groups. Ten days after pretreatment, mice are implanted intracerebral U87 glioma; and tumor volume is calculated by H.E staining after 21 days. Results show that the vessels in the contralateral brain are as control. Both 2 and 3 dimensional vessel images shown that there is no difference in the microvessels morphology on the first and fifth days after ALA-PDT compared with control. However, there is angiogenesis on the tenth days showing as decreased length, increased diameter and the number of branch points. VEGF expression significantly increased on fifth day and becomes higher on the tenth days after ALA-PDT, although there is no change on the first day; while HIF-1α expressions increased on the first day and become higher and higher. ALA-PDT with low energy can induce VEGF expression and intracerebral angiogenesis mediated by HIF-1α, and this effect promotes glioma growth in brain.

A method to reconstruct computer generated true color rainbow hologram is presented. Based on the principle of diffraction and geometric optics, the relationship between the observing window in spatial domain and its corresponding window in spatial frequency domain is analyzed. The illumination beams (red, green and blue light) are constructed and multiplied by rainbow hologram respectively. The multiplied results are analyzed in spatial frequency domain with Fourier transform. The spectral information corresponding to a specific perspective window is extracted by filtering in spatial frequency domain. And then the inverse Fourier transform is introduced to obtain the reconstructed image in the hologram plane. The reconstructed images in different positions are obtained from the object wave diffracting a given distance. The experimental results prove the validity of the proposed method. It opens up a new way to evaluate the correctness of computer generated true color rainbow hologram fast and economically.

To reconstruct a image on arbitrary tilted plane from a digital hologram, a reconstruction method based on angular spectrum transform and interpolation processing method is proposed. The angular spectrum diffraction theory is applied to analyze the proposed method. Two interpolation algorithms of forward and inverse spectrum rotations are presented. The sampling interval is analyzed based on the condition of information conservation of rotation transform. It′s shown that the interval values depend on the bandwidth of the spectrum on tilted plane and the spatial-band width product of the hologram. The holographic reconstruction is realized on a 71° single axis rotation. The partially defocus blurred aberration resulted from the tilted object plane is removed by this method. Meanwhile the range of sampling interval on tilted plane is presented.

The accurate estimation of point spread function (PSF) is the key to the image degradation model in motion blurred image restoration. An algorithm to calculate the PSF of blurring caused by uniform linear motion in arbitrary direction is presented. By computing the extent of superposition between neighboring pixels along the motion direction, the two-dimensional PSF is estimated and then used in image deconvolution to remove the motion blur. We implemented both computer simulation and imaging experiments to demonstrate the proposed approach. The image restoration performance is evaluated by comparing our method with existing algorithms via image quality metric functions.

A three-dimesional (3-D) finite element model for the numerical simulation of laser transformation hardening on the plate and inner wall of revolving body is established by means of a finite element code-Sysweld, in which the change of thermal mechanical parameters with temperature is considered and the 3-D Gaussian heat source is adopted. The temperature field, martensite distribution and residual stress field are predicted. The influence of workpiece shape on the temperature and residual stress are studied. The results show that the thermal cycles of different points on the surface direction are similar for the two model while the peak temperature of different points of inner wall model in the section direction are higher than that of the plate model. After treatment martensite can be obtained as a main phase in the hardened zone with an about phase volume fraction of 90%. The tensile stress appears in the boundary of hardening zone and heat affected zone (HAZ) and the compressive stress exists in the hardening zone. Comparing with revolving body, the value of the compressive residual stress in the center of the surface of plate is higher.

The impact toughness, residual stress, metallographic organization and fracture morphology of 2Cr13 steel quenched temperature at 920 ℃~970 ℃, tempering at 700 ℃ and laser shock processing (LSP) are investigated by means of impact testing machine, X-ray diffraction, optical microscopy (OM), scanning electron microscopy (SEM). The experimental results demonstrate that the impact toughness of 2Cr13 steel increases firstly, but decreases afterwards as the temperature of quenching rises, particularly, the impact toughness of 2Cr13 steel reaches the peak in the quenching temperature at 940 ℃, tempering at 700 ℃ and LSP. Under this condition, the residual stress is a little higher than that of the other heat treatment,and the impact fracture of 2Cr13 steel is quasi-cleavage and dimple.

The formation of laser-induced surface microstructure on silicon under irradiation with femtosecond laser pulses scanning (pulse width 42 fs, center wavelength λ=800 nm, the maximum single pulse energy 3.6 mJ) at different temperatures is described. Scanning electron microscopy (SEM) and optical microscopy are used for observing the morphologies of the surface microstructure on silicon. It is found that the area and the morphologies of the microstructure on silicon both become different. According to the observations, the energy thresholds of producing microstructure on silicon at different temperatures are analyzed and compared. The damaged area of the silicon is reduced while the temperature rising. It is shown that the energy threshold of femtosecond laser ablation silicon surface to produce microstructure increases with the temperature rising. This is valuable for the study on femtosecond laser interaction with matter, and also for the formation of surface microstructure on silicon in the future.

The surface structure features of conventional polished and magneto-rheological finishing (MRF) polished fused silica are characterized by HF based etching and thermal treating combined with atomic force microscopy (AFM). To analyze the source of thermal treating bulges, the polished surfaces are treated by three different surface treatments, namely, ultrasonic cleaning, chemical leaching, and HF etching to remove different materials on/in surface. The surface morphology after etching or thermal treating and their correlations show that there existe high-density nanoscale defects in conventional polished surface. These subsurface defects are composed of nanoscale micro-cracks and grainy impurities, which are easy to induce laser damage. Herein, a micro-cracks and grainy impurities structure model about conventional polished surface is proposed based on the analysis of material removal mechanism of polishing.

In order to deeply explore the damage characteristic and damage morphology of multi-layer optical components in inertial confinement fusion (ICF) optical system, 1053 nm laser pulses with different widths of 240, 35, 6 ps have been used to research damage ablation and damage resistant experiments at large area damage pits at 45° high reflection film. By comparing the morphology and damage resistant threshold of the ablation pits at different pulse widths, the results show that it is superior to use ultra-short pulse to repair multi-layers optical components, and the shorter pulse width is used, the better results can be got. The results of scanning ablation indicate that with the help of three-dimensional control system, the better repairing status can be got by changing the shape of the ablation pits.

Aiming at the problem of high apex angle burnt rate during laser cutting graphics with apex angle (≤30°) on mild or low carbon steel, the laser cutting experiments have been done on A3 steel board with the thickness of 3 mm by using Rofin DC025 slab CO2 laser cutting system and the method of path transformation. At the same time, the key effects of temperature on apex angle burnt have been analyzed, and the influences of path transformation and its radius on apex angle burnt rate have been studied. The results show that the apex angle burnt rate has been greatly reduced under the condition of a special cutting path, which is a circle passing through the zenith of the apex angle and its centre locating on angle bisector. Meanwhile, the apex angle burnt rate can be controlled lower than 10% under the condition of a optimal circle radius for various apex angle.

To improve the quality of laser cutting in aluminum alloy sheet, the collected melt is observed and measured. Laser cutting of 1000 series aluminum alloy sheets, with 0.85mm thickness, is carried out on a NdYAG pulsed laser machine under the different vapor-melt ratios of 0.1898, 0.2798, 0.3708 and 0.6519. In experiments the shape and size of collected removal are analyzed by a 3-D microscope. The melt is found to be tadpole-shape particles and spherical particles ranging from 71~123 μm in average diameter. The results show the collected particles are formed spherical at the high vapor-melt ratio and small in average diameter with good cutting quality. In contrast, at the low vapor-melt ratio the form is mainly tadpole-shape and the existence of big spherical particles of which with poor cutting quality. Finally, under the condition of gas pressure of 0.6 MPa and high vapor-melt ratio of 0.6519, the researches achieve higher quality cut. The results help researchers to understand the characteristics of laser cutting in aluminum alloy and improve the laser cutting quality of aluminum alloy sheet effectively.

The microstructures and mechanism of cracks forming of a thick-wall part of Rene 80 superalloy fabricated by laser rapid forming (LRF) process are presented. Results show that the solidified microstructures of LRF Rene 80 high-temperature alloy consist of directionally solidified dendrites, which are parallel with the deposition direction. The MC type carbides and γ-γ′ eutectic distribute in interdendritic region of the directionally solidified microstructure due to element segregation. The LRF Rene 80 high-temperature alloy thick-wall part contains many macro cracks, which have the length of more than 10 mm and expand along the direction parallel to the deposition direction. Analyses indicate that these macro cracks are liquated cracks. During LRF process, the γ-γ′ eutectic with lower melting point particularly along the grain-boundary regions in heat-affected zone (HAZ) melt produced by laser melting pool and result in the formation of grain-boundary liquid. On the subsequent cooling process of the HAZ, the liquated cracks along the HAZ grain boundaries occurred by decohesion across the liquid-solid interface due to shrinkage stresses of solid phase in HAZ, while the liquated γ-γ′ eutectic is still liquid.

To improve catastrophic optical damage threshold power of 940 nm semiconductor laser, the 940 nm GaInP/GaAsP/GaInAs semiconductor laser with non-absorbing window is fabricated. The impacts of rapid thermal annealing (RTA) temperature and thickness of SiO2 on intermixing are evaluated by photoluminescence spectra. The distribution of doped concentration tested by electrochemical capacitance-voltage (EC-V) method is also studied. Experimental results show that, the samples coated by sputtering method with 200-nm SiO2 shows 29.8-nm blueshift at 875 ℃ after RTA. But the blue shift of samples coated with 200-nm TiO2 by electron beam evaporation method is only 4.3 nm, which ensures a large band gap shift in the window region and maintains original band gap in gain region simultaneously. The optimized condition is used on semiconductor lasers with non-absorption window (NAW). It is found that the COD threshold is improved 1.6 times, and the output power has been greatly improved.

To obtain high energy, high efficiency Ndglass preamplifier, a Ndglass regenerative amplifier system is designed. By adjusting the single pass gain and carefully optimizing the cavity mode, the small-scale self-focusing effect in the gain medium is effectively controlled. Maximum pulse energy of 21 mJ, pulse width of 2.65 ns is obtained at the repetition frequency of 1 Hz, corresponding to a high optical-optical conversion efficiency of 5% and amplification ratio of 108. The root-mean-square (RMS) of pulse to pulse energy stability is less than 2% during 2 h continuous operation. The laser has a good beam quality of M2=1.5. The spectrum is measured to be at center wavelength of 1052.92 nm.

A 250 pJ seed pulse from 1030 nm fiber mode-locked laser is amplified by cryogenic Yb:YAG regenerative amplifier. After the seed pulse is amplified by 20 circles by controlling the electro-optical switch, the max single pulse energy is 217 μJ, the output rate is 10 Hz. Meanwhile, the spectrum decreases from 8.9 nm to 0.3 nm for gain narrowing, the corresponding pulse width is compressed from 18.0 ps to 5.5 ps, which fits the simulated result of 0.4 nm and 4.2 ps. The experimental result demonstrates that regenerative amplifier using gain narrowing can realize the require for pump pulse width and spectrum width of subpicosencond optical parametric chirped pulse amplification (OPCPA), and avoid high order nonlinear effect by fiber grating.

A high-power 2.0 μm thulium-doped ultrafast all-fiber master oscillator power amplifier (MOPA) is developed. The seed source is a thulium-doped double-clad single-mode fiber laser passively mode-locked by a semiconductor saturable absorber mirror (SESAM). It produces about 15 mW average output power with 10.4 MHz repetition rate. A thulium-doped all-fiber amplifier is used to boost average output power to 1.1 W, corresponding to the single pulse energy of 105 nJ. The pulse width is measured to be 9 ps, the center wavelength and the spectral bandwidth are 1963 nm and 0.5 nm respectively. To the best of our knowledge, this is the first report for all-fiber thulium-doped ultrafast fiber laser with watts-level average output power.

A laser diode (LD) dual-end pumped, conductively cooled, electro-optical Q-switched composite Nd:YAG laser is designed. Double-pulse laser output with adjustable pulse interval is achieved. By using two fiber-coupled LD modules as the pumping source, β-BaB2O4 (BBO) crystal as the Q-switch, double-pulse laser output is acquired by opening the Q-switch twice in a pumping cycle time, and the laser is capable of producing two Q-switched 1064 nm pulses with the single pulse energy more than 14 mJ, 18 ns, the interval between the two pulses is adjustable from 200 μs to 230 μs at the repetition of 50 Hz, the optical-to-optical efficiency reaches 24%. Furthermore, we explore the feasibility of stable double-pulse laser output by using the Q-switched crystal KD2PO4 (KD*P), and suppressing the piezoelectric ring effect of KD*P, the sub-pulse phenomenon is removed and double-pulse laser output with 11 mJ, 18 ns, is obtained.

The evolutions of the pulse propagation in gain distributed fiber amplifiers with a finite gain bandwidth are investigated with the simulation of the nonlinear Schrdinger equation. The results show that the parabolic pulse propagations in different gain amplifiers are restricted by the finite gain bandwidth. With the same input pulse and amplifier length and overall gain, the largest energy and best linear chirp output pulse can be obtained from the bidirectional gain distributed fiber amplifier. The smallest and worst linear chirp pulse output can be obtained from decreasing gain distributed fiber amplifier, while pulse obtained from decreasing gain distributed fiber amplifier is between them. Moreover, by choosing smaller initial gain coefficient, the whole gain limited by the gain bandwidth may be larger, linear chirp is better with the same overall gain.

We investigate the focus conditioning effects on molecular field-free alignment observed with high-order harmonic generation (HHG) from CO2 molecules. We also experimentally demonstrate that both the spectral shape and alignment signal of HHG significantly vary with changing focus position. A maximal alignment signal is achieved at a given focus position because of the optimal intensity of the driving laser. This intensity is related to the ionization potential of the molecules. These results indicate that a unique focus position provides an optimal alignment signal for practical applications.

Stable high-power operation of an all-fiber broadband superfluorescent source, based on ytterbium-doped double-cladding fibers, is achieved via a fiber amplifier. It comprises an amplified spontaneous emission (ASE) seed source which is amplified to over one hundred watts in the next stage for a single pass, with no self-pulsing, relaxation oscillation or lasing modes being observed. The center wavelength of ASE seed source is 1050 nm, and the full width half maximum (FWHM) is 21 nm. The maximum superfluorescent output power yielded by the amplifier is 102 W, the slope efficiency with respect to the pump power is 70%, and FWHM of the emission spectrum is 20.5 nm.

Photonic crystal laser cavity with one-dimensional (1D) photonic bandgap is investigated by plane wave expansion method and finite-difference time-domain method. The photonic crystal laser cavity with quality factor Q of 2.2×106 and mode volume V of 0.278(λ/n)3 is achieved. The relationships between tapered section, mirror section, defect section, and Q are analyzed. The introduction of tapered section, choosing proper periodic number and suitable defect length can improve the performance of the cavity. These conclusions provide an effective theoretical analysis and guidance on optimization of photonic crystal cavity with 1D photonic bandgap.

The impact of subsurface cracks on the laser damage resistance of bare and anti-reflection (AR) coated fused silica are experimentally investigated using chemical leaching. Two kinds of substrates with the subsurface cracks number density of obviously different are obtained by retaining or removing the grinding cracks. To highlight the effect of the subsurface cracks, the photoactive impurities in the polishing layer, as a competing damage mechanism, are minimized by chemical leaching. Then the HfO2/SiO2 anti-reflection coatings are deposited by electron beam evaporation. 355 nm laser-induced damage threshold (LIDT) test results and damage morphology analysis verifie the negative effect of subsurface cracks on the LIDT of AR coated surfaces. According to the heating morphology of polished fused silica surface, a coupling model between the subsurface defects of substrate and the laser damage of coatings is proposed.

To obtain the precise optical constants of thin films, LaF3 thin films of different thickness are deposited by Mo-boat evaporation on fused silica (JGS1). A model for extracting the optical constants of weak absorbing film is applied, which is based on spectrophotometry. The refractive index n and extinction coefficients k of the thin films and substrate are obtained in the range of 185~450 nm. It is found that the refractive index inhomogeneity of LaF3 thin films decreases as the film thickness becomes thick. The calculated optical performances curves fits the experimental ones well when the inhomogeneous model is employed, which can improve the precision of thin film′s optical constants determination.

Based on the multi-beam interference principle, a Gaussian beam reflected-intensity expression on a non-parallel angle-tuned thin-film filter in oblique incidence is derived. The influence of the reflected-intensity distribution with different incident angles, especially with different wedge angles of the non-paralleled thin-film filter is analyzed theoretically. Calculation and experimental results show that the reflected-intensity distribution, reflected-peak and the isolation degree are influenced by the wedge angle, incident angle and polarity of the wedge angle. In order to get stable reflected-characteristics and high isolation degree, the parallelism of the angle-tuned thin-film filter should be improved in fabrication or the polarity of the wedge angle in oblique incidence should be negative.

Camera calibration aims at building up the mapping relationship between 3D world coordinate and 2D image coordinate. The traditional calibration board contains dozens of neatly arranged standard circles or grids. Calibration is completed by extracting the center coordinates of standard circles or grid corner coordinates. In a micro-object measurement system, the camera field of view is very small and camera cannot extract enough points from the calibration board. To solve this problem, a new method based on conic and lines is proposed. This method uses conic and lines equation instead of points to calibrate so that enough information can be extracted from calibration board even under small field of view. Both computer simulation and real data test show that the proposed method has higher accuracy and better robustness. In addition, the calibration board is a standard semicircle which is very easy to be made and easy to be used under small field of view.

To overcome the shortcoming of traditional fast Fourier spectral analysis method that it can′t be applied to the nonstationary signal and can not achieve precise measurement of the micro-displacement variation based on all-fiber laser interference, a discussion on the phase demodulation algorithm using the continuous wavelet transform (CWT) for non-stationary signal is presented. In the frequency domain of the digital signal, the transient characteristics extracting based on the wavelet ridge is analyzed, through which the phase of the wavelet ridge is received. And then the micro-displacement of the object is experimentally obtained. According to the proposed method, the theoretical analysis and the computer simulation are realized. Finally, the micro-displacement variation is obtained from the experimental interference signals by using the method. Comparing with traditional fast Fourier transform (FFT) method, the result of method is of higher accuracy. Experimental results show that the algorithm proposed is of high precision, low complexity, good robustness, and will have a broad prospect of application.

The observation system of solar velocity field can be used to detect the activities of helioseismology, which is important for the study of the solar internal structure. The method of using K-FADOF to observe the velocity field of photosphere is studied, which takes advantage of the Faraday anomalous dispersion optical filter (FADOF), such as high spectral resolution and spectral stability. This method utilizes K-FADOF to distinguish the Doppler shift of potassium line (769.898 nm) which comes from the Sun′s Photosphere, uses the F-P etalon to select the single-peak signal transmitted through the K-FADOF, and receives photosphere′s Dopplergram. The prototype of K-FADOF is developed and tested. The experiments show that its experimental transmission spectrum pattern almost coincides with its theoretical pattern. It indicates that the K-FADOF meets the requirements of observing the solar velocity field of high spectral resolution. Further, it can achieve to observe simultaneously multi-layer velocity field of the solar atmosphere with this technology extended to the solar other lines.

Hollow-core Bragg fiber is a kind of photonic bandgap fiber which has a cladding of one dimensional photonic crystal (1DPC) and an air core. Aiming at its application on CO2 laser transmission, a hollow-core Bragg fiber sample with a transmission band of 10.6 μm is designed and fabricated. Its transmission spectrum is measured by Fourier transform infrared spectrometer (FTIR), showing an obvious low loss transmission peak at 10.6 μm. Measured by cutback method using a CO2 laser, the transmission loss at 10.6 μm of the fiber sample is 2.35 dB/m. The additional loss induced by fiber bending is also measured under different fiber curvatures, showing that it rises with increasing curvature. Experiments show that a fiber bending of 90° with a bending radius of 10 cm near the fiber output end leads to an additional loss about 2 dB. The experiment results demonstrate the low loss transmission of CO2 laser by the hollow-core Bragg fiber sample, showing its great potential on improving the flexibility of CO2 lasers.

A gyro output is influenced greatly by the fluctuation of a modulation triangle waveform in integrated optical resonator gyroscopes (IORG). The curve of scale factor K of the gyro with modulation waveform parameters (MWP) is induced. The influence on the output characteristics by MWP distortion is discussed. The relationship between the nonlinearity and MWP undulation is simulated. An IORG experimental system is carried out, and the triangle wave is generated by high-frequency waveform generator. Dynamic range of ±500(°)/s with nonlinearity of 0.96%, and bias drift of 0.69(°)/s with integration time of 1 s over 1 h are obtained. The testing result verifies correctness of the simulation.

Brillouin optical time domain reflectometer (BOTDR) is a distributed optical fiber sensor with broad application prospects. For a given input light wavelength, the Brillouin frequency shift of spontaneous Brillouin scattering light has a linear relationship with both temperature and strain. The distributed temperature or strain can be obtained by measuring the Brillouin frequency shift (BFS) along the fiber. In a BOTDR, Brillouin power spectrum scanning is a commonly used means to obtain the BFS, and there has been two types: the optical frequency-difference scanning method and the electrical frequency scanning method. A wavelength scanning BOTDR is proposed based on the wavelength dependence of the BFS. With a tunable laser as the light source, the Brillouin power spectrum is obtained by scanning the input light wavelength. This method combines the advantages of the optical frequency-difference scanning method and the electrical frequency scanning method. The feasibility of this proposed method is demonstrated experimentally. By use of this method, a temperature accuracy of 2.2 ℃ along a 23.4 km sensing fiber with a 5 m spatial resolution is achieved.

A phase sensitive optical time domain reflectometer (OTDR) technology based on the digital coherent detection and Wiener filter is proposed and analyzed, in which the phase and amplitude of the Rayleigh scatting light along the fiber link can be demodulated in real time. Using the proposed method, the vibration position, frequency and intensity for a sinusoidal disturbance signal driven by a lead zirconate titanate (PZT) on a 3.5 km single mode fiber link are obtained exactly. Wiener filter is used to reduce the laser phase noise and additive noise caused the phase fluctuation. A spatial resolution of 5 m for the system is realized.

To overcome the accuracy limits of fringe counting method for a Fabry-Perot (F-P) interferometer and the complexity of a higher resolution demodulation system such as phase generated carrier (PGC), linear frequency modulation (LFM) and heterodyne frequency modulation, where residual amplitude modulation always exists in frequency modulation, a dual-fiber F-P displacement sensor based on double-fiber phase demodulation is presented. The proposed demodulation scheme eliminates the modulation on light source, improves the accuracy, and keeps the system cost as low as that of the fringe counting method. Compared with the reported dual-fiber F-P structure, this design has no strict requirement for a specific phase difference between the two interference paths, which makes it more feasible for manufacturing. Experimental results demonstrate a good linearity of 1.1% and a resolution of ±3 μm within a measuring range of 0~500 μm for the sensor system.

A hollow dual-core photonic crystal fiber (HC-PCF) filled with high refractive index liquid sensitive to temperature is analyzed. The coupling properties and the inter-model dispersion are investigated by using full-vector finite element method (FEM). Theoretical results show that with the increase of the wavelength, the coupling coefficient will decrease first and then increase for a certain temperature. Especially, the zero inter-modal dispersion can be achieved at a particular wavelength. By adjusting the temperature and/or the structure parameter d/Λ, zero inter-modal dispersion in an extremely wide wavelength range including both 1.31 μm and 1.55 μm is realized. This implies that the pulse distortion effect due to the mismatch between different modes can be eradicated and 100% power transfer can be realized in such a hollow dual-core photonic crystal fiber.

We present the design of a novel bi-directional millimeter-wave radio-over-fiber (mm-RoF) system based on the millimeter-wave generation by optical frequency multiplication (OFM). A dual-drive Mach-Zehnder modulator is used to generate high-order optical side-modes which beat in the photo-detector, producing a 40-GHz carrier. Over 100-Mb/s orthogonal frequency division multiplexing (OFDM) modulation scheme is employed. The emphasis is on developing a mathematical model for optimizing optical modulation index to the Mach-Zehnder intensity modulator (IM) for OFDM signal with high peak-to-average power ratio which imposes a limitation on the system bit error rate (BER) performance due to the non-linearity of IM. The theoretical analysis on composite carrier to composite triple beat ratio is performed based on which extension to the system BER formula for quadrature phase shift keying/ multiple quadrature amplitude modulation (QPSK/MQAM) format is presented. The experimental proof is given in a 40-GHz RoF system at a bit rate of up to 280 Mb/s in 100-MHz bandwidth.

To compensate the drift of fiber loop length in fiber-optic parametric oscillator (FOPO), a novel feedback control scheme based on four-wave-mixing idler power is put forward. The feasibility of this scheme is confirmed by the clock extraction experiments for 10 Gbit/s optical return to zero (RZ) signal, and the normalized phase and amplitude jitter of less than 0.015 and 0.06 can be achieved under long-time stable operating condition. Thus, the scheme proposed in this paper is of practical applicability for the FOPO′s stability of oscillation.

Terahertz (THz) imaging has the advantages that THz radiation can penetrate most nonmetal and nonpolar materials for concealed objects detection, while it is harmless to the organisms. THz reflection-mode imaging has a more widely application range. Thus the penetrating ability for common packaging materials and clothes becomes very important to evaluate a THz reflection-mode imaging system. Therefore, penetration experiments are carried out by using a 2.52 THz reflection-mode scanning system. The system is constructed based on a CO2 pumped THz laser. The imaging targets are a razor blade, a penciled character, a 50 cents coin, a metal commemorative coin, and Siemens star. Papers, paper envelopes, and lab gowns are used as the shelters, and the imaging results are compared and analyzed. The experiment results demonstrate that the system can image through one layer of the lab gown or a paper envelope. The maximum insertion loss approaches 42 dB.

In order to direct the truss design of remote sensing camera, the influence of various modulation transfer function (MTF) on camera system is analyzed to satisfy the requirement of system MTF, thus the main support structure is designed by the limit of optical diffraction MTF. The minimum optical diffraction MTF under the situation of truss structure is calculated from the actual MTF, assembly and electronic factor of on-orbit production. Then the MTF is analyzed only by employing the pupil function under various kinds of obstruction because the optical software cannot evaluate the optical diffraction MTF entirely. It is concluded that the max diameter of tri-truss is 38 mm, the max diameter of four-truss is 26 mm. The truss structure of 26 mm diameter and 4 mm thickness is satisfied the specifications of satellite design by analyzing the static deformation and modal frequency of various wall thickness through finite element analysis (FEA).

Lithography is the most important technology when manufacturing of large scale integrated circuit. Since the resolution of a lithographic tool is determined by the performance of the imaging optics. The surface accuracy of lithographic projection objectives is on nanometer scale. It is obvious that the fabrication of such high-quality optics and single lens supporting requires tremendous efforts. In order to design the structure of single lens supporting with high-precision, the surface form of single lens is studied, under gravitational condition. Then, the support structure is analyzed in detail by finite element method (FEM) and a new type of flexible support is presented. Analytical results indicate that the surface figure accuracy of the mirror reach peak valley (PV) of 15.4 nm and root mean square (RMS) of 3.62 nm under the load case of gravity. In order to accept high accuracy for optical surface form analyses by FEM, a new method which could remove the surface form of reference surface and the original surface form of tested surface is built. According to the method, the differences of PV magnitudes and RMS values are only 2.356 nm and 0.357 nm, respectively. The results show that the proposed kinematics mount structures satisfy the mechanical requirements of mounts for 193 nm projection lithographic lens.

Time-integrated X-ray spectra produced by aluminum wire-array Z-pinch plasmas are measured with a novel mica uniform dispersion crystal spectrograph at Yang accelerator. By using the collisional-radiative equilibrium (CRE) model, the average electron temperature is estimated to be 500 eV from the intensity ratios of Ly-α/He-α line and Ly-β/He-ε line. The plasma core electron temperature is around 1215 eV derived from the continuum slope with linear fitting. The experimental result demonstrates that the electron temperature shows a nearly linear decrease from the axis to the outer edge of the pinch in this implosion. It is shown that the intensity ratio is an efficient tool for inferring electron temperature and the continuum slope provides essential information of core electron temperature of aluminum wire-array implosion.

Terahertz spectroscopy provides a new way for material identification. Investigation on establishment and usage methods of terahertz spectral database is needed so as to distinguish unknown substances. In order to establish the database, terahertz spectra of twenty organic materials are measured by own built terahertz time-domain spectroscopy system and the interference information of baseline and noise are removed by wavelet transform. The usage of database is divided into two steps: 1) determine whether the unknown substance is in the database through the radial basis function neural network; 2) identify the material if it is in the database by multi-class support vector machine. The fault tolerance of the algorithm is improved combined with error-correcting output coding to handle the multi-class problem with recognition rate of 96.7%. The network also has a good prediction of materials outside database with recognition rate of 93.2%. The establishment and usage methods of the database suppress the system noise and can be applied to practical situations.