A laser diode (LD) continuous-wave (CW) end-pumped high repetition rate electro-optic (EO) Q-switched Nd:YVO4 laser was experimentally and theoretically studied. In experiments, using LGS(La3Ga5SiO14) single crystal as an EO Q-switch, with 28 W pump power, an output pulse train with 70 kW peak power, about 7 ns pulse duration and more than 5 W average power was obtained at 104 Hz repetition rate. And the Q-switched output performance at different repetition rate was compared. In theory, by solving the amendatory actively Q-switched rate equations, taking amplified spontaneous emission (ASE) into account, a series of results consistent with experiments were achieved. In the last, the thermal lens effect of end-pumped solid state laser was simulated by LasCad software and measured through experiments, the calculation results were almost identical to the experimental values.

Low coupling efficiency of transverse electric (TE) polarization waves by using binary gold diffraction gratings for side-coupling of double-clad fiber lasers is demonstrated theoretically. Meanwhile, a new multilayered structure for side-coupling of TE-polarization waves is proposed and the coupling efficiency as high as 72% is achieved by using three layers gold strips with different widths. And the higher efficiency with much more layers gold strips is predicted. The relationship between the line-width of multilayered gold grating and the efficiency of +1 and -1 order backward diffraction wave is analyzed.

A set of high explosive pumped photolytic iodine laser system was built and a steady laser output of approximate 100 J was obtained in experiments. The radiation spectra of shock wave produced by high explosive in argon of about 101.325 kPa were measured, meantime the velocities of shock wave were also measured by photography. In the experiments, the alkyl iodine C3F7I was used as laser working substance and a good waveform of laser was obtained. The full width at half maximum (FWHM) of laser pulse is about 34 μs and minimum angle of radiation is less than 20 mrad. The principle and technique routines were introduced in the paper. The experiments under different conditions were carried out and the expenimental results were listed and analyzed. The factors that influence the laser output had been discussed. This technique progress made it possible for making a larger energy explosive-driven iodine photodissociation laser.

Aiming at the restriction of the number and the thickness of elements used in the inertial confinement fusion (ICF) system, especially in the final optics assembly, and utilizing the characteristic of easy integration of diffractive optical element(DOE), a new means to fabricate color separation grating (CSG) and beam sampling grating (BSG) on two surfaces of one fused-silica substrate with two-surface exposure method is presented. Thus the functions of harmonic wave separation and beam sampling are realized through one silica plate. The masks of CSG and BSG are fabricated by photolithograph and e-beam direct writing method, respectively, and the ion beam etching method is used in fabricating the combined CSG-BSG element. The experimental results show that the parameters such as energy utilization ratio, color separation ratio and sampling efficiency for 3ω harmonic wave are in accordance with those of separated CSG and BSG elements, which achieve the basic technical requirements of the final optics assembly of ICF driver.

Laser imaging radar has high space resolution, and can output four-dimensional (4D) image (intensity image+three-dimensional (3D) range image), so it is fit to be the sensor of target recognition. Support vector machine (SVM) is a way of target recognition, which has high correct recognition rate, in the case of learning with small samples. Through optimizing the algorithm of SVM, it is embedded into digital signal processing (DSP) of laser imaging radar, achieving the function of target recognition, which has high practical meaning. The experiments with the real intensity images of laser imaging radar are finished. In the experiments, the testing set totally has 56 samples, and the costing time is 31.97μs, which can state that the algorithm can meet the real-time requirement, and the correct recognition rate is 98.2%. Another experiments with simulated range images of laser imaging radar validate the generalization of SVM. The experiments results show that SVM can meet the recognition demands of laser imaging radar in the real-time and recognition performance.

To study the effect of transversely excited atmospheric (TEA) CO2 laser pulse waveform on the momentum coupling coefficient, the waveform of laser pulse was changed, and the pulse duration was compressed about to 50% by controlling the pressure of the gas and proportion of components in gas mixture. According to that, some experiments and numerical calculation were done. Achieved results indicate that increasing the coupling coefficient is very favorable for decreasing the proportion of energy between the forepart and the whole pulse in TEA CO2 laser propulsion. Also, the coupling coefficient can be effectively raised while pulse duration is bigger than characteristic time of two-dimensional movement.

Displacement of the scattering media from speckle information can be obtained. So a novel femtosecond laser speckle technique was proposed. For measuring the displacement of a scattering object by using two images which are taken before and after the object moved. Since the two images are recorded by a charge coupled device (CCD) camera and stored on separate frames in computer, it is possible to use a cross-correlation algorithm to determine the displacement field in real-time. In experiment, displacement of the scattering media is in agreement with the result obtained by cross-correlation algorithm. It is shown that femtosecond laser speckle cross-correlation technique should be a useful for measuring the movement of a scattering object under femtosecond laser illumination.

The group velocity matching and group velocity dispersion have been investigated for noncollinear optical parametric amplification with periodically poled KTiOPO4 (KTP). A general mathematic model for evaluating the spectral bandwidth of optical parametric amplification (OPA) is developed. The spectral bandwidth is determined by expanding the wave vector mismatch in a Taylor series and retaining terms through second order. If the first-order term vanishes, noncollinear interaction tree waves are group matching. And the spectral bandwidth is determined by group velocity dispersion. The dependences of gain bandwidth on crystal length and pump intensity are also studied. Selecting appropriate grating period, wider tunable range can be obtained with group velocity matching. The parametric bandwidth is relating to crystal length, noncolinear angle, group velocity and group velocity dispersion. Because group velocity is matched, the parametric bandwidth is very large. The effective nonlinear coefficient is nearly equal to d33. And maximum effective length and conversion efficiency are enhanced largely.

Carrier-envelope phase (CEP) stabilized 6 fs ultrashort intense pulses were generated by focusing 40 fs (full width at half maximam (FWHM)) 1.1 mJ (pulse energy) intense laser pulses into the hollow fiber filled with argon gas. The input pulse was broadened by self-phase modulation and the spectrum was compressed by chirped mirrors and two titled quartz thin wedges. We applied the compressed pulse to the experiment of high-order harmonic generation and found it supporting a transform-limited 500 attosecond single pulse in time domain.

The nonlinear dynamic characteristics of distributed feedback (DFB) semiconductor lasers subjected to external optical injection have been investigated experimentally, and the output dynamical characteristics are mapped as a function of the power of optical injection and the frequency detuning between the injection frequency and free-running frequency of the unperturbed DFB semiconductor laser. Experimental results show that DFB semiconductor lasers are very sensitive to external perturbation and can exhibit periodic, chaos and other complex nonlinear dynamical characteristics when subjected to different external optical injection. There exist three regions of complex dynamics in the map. The complex dynamics is always related to the multi-periodic dynamics. When the laser exhibits complex dynamic, its spectrum is continuous spectrum, and there are several peaks in the spectrum. The magnitude of frequency that the peaks correspond to respectively has nothing with the power and the frequency of injection field.

Absorption length has an influence on signal to noise ratio (SNR) and slope of modulation transfer spectra. An equation of modulation transfer spectroscopy was derived by dividing absorption length into n units and integrating signal of every unit. Theoretically the relative signal intensity and central slope of spectrum with different absorption length were calculated according to the equation, from which optimal absorption length was obtained. Finally both SNR and slope of modulation transfer spectra of I2 with different absorption length were compared experimentally while I2 cell temperature was held at -15 ℃. The results of comparison showed that modulation transfer spectra was optimal at three-pass (120 cm). The frequency stability of 9×10-14 at 1 s integration time at three-pass was estimated. So it is promising for improvement of laser frequency stability when modulation transfer spectra with optimal absorption length are used in laser frequency control.

In order to investigate the third-order optical nonlinearities of a novel type of organo-metallic compound, ［C16H33(CH3)3N］Ni(dmit)2 (dmit2-=4,5-dithiolate-1,3-dithiole-2-thione), abbreviated as CTNi, a sample solution with concentration 1.0×10-4 mol/L in acetone was prepared and its third-order optical nonlinearity was investigated using Z-scan technique at 1064 nm with 40 ps laser duration. Strong saturable absorption was found, the excited states effective absorption cross section was σeff=1.47×10-18 cm2, and the corresponding nonlinear absorption coefficient was β=-4.36×10-12 m/W. In addition, Z-scan curves revealed a self-defocusing effect with a large negative nonlinear refraction coefficient n2=-1.55×10-18 m2/W.

Third harmonic generation (THG)of super intense femtosecond laser pulse with one BBO crystal was analyzed. Effects of the third-order and the cascaded second-order nonlinearity in one crystal on the third harmonic conversion efficiency were compared. Influences of the factors, such as input fundamental intensity, length of the crystal, self-phase-modulation (SPM) and cross-phase-modulation (XPM), group-velocity mismatching, detuned angle, azimuth angle, etc, on the conversion efficiency, pulse shape and spectra of the third harmonic field were discussed in detail. Furthermore, the methods to improve the third harmonic conversion efficiency were proposed. The results show that, the variation of the maximum intensity and the pulse width (full width at half maximum (FWHM)) of the third harmonic field with the length of the crystal is not obvious. By justifying the phase-mismatching angle of the fundamental field, the conversion efficiency and the maximum intensity of the third harmonic field can be increased, and the pulse width (FWHM) can be reduced. Moreover, it is also helpful to improvement of the conversion efficiency by optimizing the azimuth angle of the crystal.

Pulse-width expansion of an ultra-short Gaussian pulse in nonlinear optical crystal because of low order group velocity dispersion (GVD) was theoretically analyzed. Optical parametric interaction processes of the CsLiB6O10 (CLBO) crystal with a negative uniaxial and 50 fs ultra-short Gaussian pulse have been considered. Mechanism of ultra-short Gaussian pulse broading with or without initialization chirp modulation was numerically calculated. The pulse-width is expanded heavier in ordinary light than that in extraordinary in short wavelengths. The shorter pulse wavelength, the heavier pulse-width expanded. When the crystal length is equal to the crystal dispersion length, the pulse-width has been expanded 2 times than the initialization. Also, the shorter the dispersion length is, the more obviously the pulse-width is expanded.

The diffraction properties of a volume grating for a pulsed laser beam with Gaussian-profile both in time and space domain are studied, using two-dimensional (2D) coupled-wave theory. Analytical expressions for the spatial and spectral profiles of the transmitted and diffracted beams are obtained. The influences of geometry parameter on the Bragg diffraction properties and the diffraction efficiency of the pulsed Gaussian beam are discussed. It is shown that the Bragg selectivity bandwidth and the diffraction bandwidth of volume gratings are broadened when geometry parameter g increases. The diffraction efficiency increases when pulse duration increases and trends to a saturated value, the smaller the geometry parameter g is, the slower the saturating velocity is, and the larger the saturation value is.

Based on the assumption of single-scattering, atmospheric propagation model of non-line-of-sight optical scattering communication system is studied. The model is used to analyze the correlations between received scattered energy and parameters of system, including source divergence angle, receiver field of view, and apex angles of transmitter and receiver in an optical scattering communication system. Contribution of atmospheric molecular scattering and aerosol scattering of received scattered energy is discussed. The results show that received scattered energy is attributed to molecular scattering at larger transmitter and receiver apex angles, but with the decrease of apex angles, aerosol scattering will be dominant in received scattered energy. Enhancing of the receiver field of view can effectively improve the signal noise ratio for communication systems operating in the solar-blind ultraviolet (UV) spectral region. In addition, the evolution tendency of received scattered energy versus the source divergence angle is inverse for two typical transmitter and receiver apex angles. This result suggests that divergence angle of source should be designed according to specified situation.

The optical parametric chirped pulse amplification (OPCPA) is a reversible nonlinear course. When the signal reaches its peak density, the pump power has been almost depleted. After this point,the over-saturating OPCPA course begins and the energy from the signal and idler reverses to the pump. A new method of the chirped-pulse spectrum shaping is put forward in this paper based on the above course. The theory of the new spectrum shaping method is explained by simulation. Also by simulation it is shown that by varying the pump intensity or adjusting the phase matching angle or changing the pump waveform, the output of spectrum shaping can be effectively controlled; even when signal and pump pulses are under the proper synchronous conditions, a frequency shift occurs at amplified signal, and the spectrum red-shift induced by Ti:sapphire saturation amplification may be suppressed.

For the free space optics (FSO) communication system, the atmospheric channel′s signal-noise-rate (SNR) is a key factor, and the FSO system based on twofold turbo code is proposed. First, the atmospheric influence on FSO system and the character of atmospheric channel are analyzed, the SNR of atmospheric channel versus the weather visibility is deduced, and the coding and decoding principles of twofold turbo code are analyzed. Applied the function of atmospheric channel′s SNR, the SNR of atmospheric channel versus the weather visibility and the bit error rate (BER) of FSO system based on twofold turbo code and common turbo code are simulated. The results show that, for an applied optical wireless communication system, under the condition of system′s BER being below 10-5, the channel′s SNR of system based on twofold turbo code is 1dB lower than that based on common turbo code. So, for the same channel′s SNR, the twofold turbo code is more efficient to degrade the system′s BER than common turbo code.

A compensation method with theoretical analysis is proposed to compensate the instability of interrogation by using a pair of fiber Bragg grating (FBG) with different thermal coefficients. The factors that influenced the stability of interrogation had been investigated. Several sensors were installed in Donghai Bridge and formed a sensor network. The signals from sensors were demodulated by the improved interrogator on the final test of Donghai Bridge, which shows good performance.

A technique for automatic measurement of the refractive index of liquid was proposed. The approach based on the principle of the equal thickness interference of air wedge and charge coupled device (CCD) image-processing technique. The unitary linearity regress method was used to fit the relation between the serial number of the CCD pixels and the serial number of the intensity maximum of interference fringes, and the regress coefficients were used to compute the refractive index of liquid. Some factors affecting the quality of fringe patterns were taken into account and perfect fringe patterns were obtained by removing background light. The experiment result proves the feasibility of the new method. The relative error of the refractive index of water is 0.09%. In order to obtain clear interference fringes in other optical experiment, the new method of removing background light is worthy to be considered.

As white noise, random drift is a key essential affecting the precision of laser gyro. Digital filtering can reduce the effect of the random drift. Some familiar digital filtering methods are studied in the article, i.e. the AR (2) model, Kalman filtering, wavelet analysis and wavelet packet analysis. The effects of different filtering methods are analyzed and compared with both power spectrum and Allan variance. Experiments indicate that Kalman filtering can achieve best performance as to filtering the random drift of ring laser gyro, and high frequency noise can be filtered to some extent by using wavelet analysis and wavelet packet analysis. These results are useful to the applications of laser gyro.

Fire related gas sensing technology has been used to fire detection and has been regarded as a promising way for early fire warning, especially the optical absorption based gas-sensing. It can offer high sensitivity, low false alarm rates and early fire warning. A tunable diode laser absorption spectroscopy based fire gas detection system has been developed. The system used fiber-coupled near-infrared telecommunication distributed feedback (DFB) tunable diode laser as light source. Simultaneous detection of the two most common fire gas products, CO and CO2, was realized by modulation frequency multiplexed dual diode lasers. The system minimum detection limit for CO was estimated to be 0.00375 mg/m3 (3σ), and can meet the demands of in situ measurements of fire related gases.

A theoretical model is presented which computes the pulse laser scattering echo power from the whole dimension target by using the theory of rough surface scattering and of pulse laser scattering combined with the modeling parameter of complex rough surface. The directional figure of pulse laser backscattering echo power is given through the measurement of the pulse laser backscattering echo power of the aerial complex scale-model. An analysis of the experimental error by comparing the theoretical results with experimental data proves that this model is correct. Computational results of the pulse laser backscattering echo power from non-cooperative complex space target by the model can pre-estimate the laser scattering characteristic of space target and solve some problems of engineering application about the pulse laser scattering from space complex targets.

To reduce the nonlinearity of nanometer measurement in laser heterodyne interferometric, the influence mechanics of nonideal splitting performance of polarization beam splitter (PBS) upon nonlinearity must be confirmed. In the paper, nonlinearity model is proposed when polarization transmissivity and reflectivity are not ideal. Model is also proposed to describe how the nonideal splitting performance of PBS influences the second-harmonic nonlinearity. The simulation results show that influence of nonideal polarization transmissivity and reflectivity on nonlinearity is the first-harmonic and the influence will be serious while the splitting performance of PBS gets worse. When reflectivity is 0.90 and transmissivity of PBS reduces from 1 to 0.90, nonlinearity increases from 0.62 nm to 1.24 nm. When the rotation angle error of PBS exists, the second-harmonic nonlinearity caused by the nonideal splitting performance of PBS will be ineffective, but the first-harmonic nonlinearity will increase and the nonlinearity is influenced greatly. It is assumed that the rotation angle error of PBS is 5° and transmissivity of PBS reduces from 1 to 0.90, nonlinearity increases from 0.39 nm to 1.41 nm.

Retrieval method for aerosol mass concentration vertical distribution with lidar is one of research contents in environment monitoring fields. Making use of the extinction coefficients on ground gained by lidar and corresponding mass concentrations gotten by the tapered element oscillating microbalance (TEOM), the relationship between extinction coefficient and mass concentration can be disclose, then the mass concentration vertical distribution can be retrieved through the extinction coefficient vertical distribution. Based on it, two models are adopted, and confirmed by some experiments. It is indicated that the aerosol mass concentration vertical distributions retrieved by both the models are consistent with each other, and consistent with facticity. The models are maneuverable and simple, and can monitor online and real-time.

The effect of modulation frequency on phase demodulation is analyzed in sinusoidal phase modulating (SPM) interferometry for displacement measurement. A rule for selecting modulation frequency is presented. The spectrum of interference signal is analyzed. It is found that when the displacement measurement range is narrow, small modulation frequency can meet the phase demodulation need; when the displacement measurement range is enlarged, modulation frequency has to be increased. Simulated data and experimental results indicate that with an λ/4 increase in amplitude of vibration to be measured, modulation frequency is required to increase to four times as frequency of vibration to be measured, where λ is the wavelength of light source.

A laminated model of cutting face for evaluating cutting quality has been built up on the basis of cutting experiments. The experimental results and the theoretical analysis of the model show that, the lower part of the cutting face, adjacent to the bottom edge, has the worst cutting quality due to its worst roughness. The quality of the bottom face is mainly depended on the temperature of the lowest part of cutting front. Therefore, the method with this roughness as the main criterion for quality evaluation and detection is reasonable. The behavior of sparks has also been investigated by side imaging the sparks jet. It is found that the sparks behaviors are related to both the cutting speed and the roughness of the bottom face. The maximum temperature at the exit of sparks occurs at the status of the best roughness of the bottom face, which relates to the optimal cutting speed. Based on the method, on-line quality monitoring of lowest part of cutting front has been realized.