A laser diode (LD) pumped Nd3+ KY(WO4)2 (NdKYW) blue-green laser is reported. LBO (LiB3O5) crystal with type Ⅰ critical phase matching was used for intracavity frequency doubling. The threshold pump power is 400 mW. The laser performance at 530 nm was demonstrated. The maximum CW output power of 200 mW was obtained with an incident pump power of 2 W. The optical-to-optical conversion efficiency of frequency-doubled output is about 10%.

The micro-cavity Cr4+:YAG/Nd:YAG passively Q-switched laser pumped by pulse-pump and pre-pump mechanism is investigated theoretically and experimentally. The experiments show that with large pulse width and high repetition rate of pump pulse, the dependent jitter scope of output laser pulse with pump pulse is increased. By reducing pump pulse width and repetition rate, the 1.06 μm laser with 3.8 ns pulse width and single pulse energy of 65 μJ is obtained. The dependent jitter scope of output laser pulse with pump pulse is lower than 0.8 μs. At the same time, the advantage and disadvantage of pre-pump mechanism is analyzed.

Pulsed blue laser has important applications in underwater detection, underwater communication and remote sensing. According to the ABCD matrix of Gaussian beam's propagation, a Z-type cavity insensitive to thermal lens effect is designed. By use of 808 nm laser diode (LD), the 4F3/2→4I9/2 quasi-three-level transition in Nd:YVO4 crystal is realized at room temperature. Stable pulsed 457 nm blue laser with high repetition rate and high peak power is demonstrated by acousto-optically Q-switching and intracavity frequency doubling. When the incident pump power is 30 W, the maximum single pulse energy of 56 μJ, pulse duration of 217 ns and peak power of 258 W are achieved at 10 kHz; the maximum average power of 760 mW, pulse duration of 261 ns and peak power of 146 W are obtained at 20 kHz. The fluctuation of the blue laser power is less than 2.0% within the given 20 min at the maximum output power.

Pulse-amplitude equalization through a nonlinear-amplifier-loop mirror in active rational harmonic mode-locked fiber laser is designed and experimentally demonstrated. An optical pulse train with a high repetition rate is generated when the modulation frequency is tuned to a rational number of the cavity's fundamental frequency of the fiber laser. Through incorporating a nonlinear-amplifier-loop mirror into the cavity, the pulse train can be equalized by adjusting the DC biased voltage and the modulation depth. At the modulation frequency of 1 GHz, an amplitude-equalization pulse train with repetition rate of 4 GHz or 5 GHz is obtained.

The generation of nanosecond-scale pulsed laser with stimulated-Brillouin-scattering (SBS) phase conjugation in fiber was investigated theoretically and experimentally. Numerical simulation was performed to study the waveform and the sequence of laser pulse. The obtained waveform is coincident with the curve describing the relationship between reflectivity of SBS phase conjugation mirror and time. The results show that changing Q value in resonant cavity by utilizing SBS phase conjugation is feasible. To investigate the output laser at different lengths of SBS medium, an all-fiber Er3+-doped Q-switched laser was designed. When the length of single-mode-fiber (SMF) is 1.5 m, laser pulse are generated with pulse duration of 2.6 ns, pulse period of 58.23 ns, average output power of 7.35 mW at pump power of 45 mW. When the length of SMF is decreased to 1 m, pulsed laser with remarkable dual-peaks is obtained with pulse period of 26.47 ns. While the length of SMF is increased to 2 m, only irregular stochastic pulsations are observed. Experimental data indicate that the length of SBS medium is vital to the formation of phase conjugation mirror. If it is too long, pulsed laser can not be generated for the lack of fixed conjugation relation between Stokes lines, and on the contrary, dual-peaks laser pulses occur for the change of photon lifetime in orthogonally polarized modes. Once the laser pulses are generated, their characteristics are only correlated with the stochastic characteristics of SBS and the pulse profile maintains constant with the increase of pump power.

To realize energy balance and power balance of high-power solid-state laser facility, laser performance simulation model (LPSM) is developed to provide real-time prediction for the Technical Integration Line (TIL). This model is used to determine the system setpoints, such as injection energy, injection pulse shape, attenuations, and laser diagnostic settings. Injection energy is predicted by fitting the amplification curve based on diagnostic energy feedback from previous TIL shots, input pulse shape for flat-top pulse output by iterative loop method, temporally shaped pulse shape by the method of gain-fluence curve, and laser power and energy for laser diagnostic settings by beam propagation and amplification code named SG99. Real-time adjustments of the model parameters allow the LPSM to predict energy within 5%, and provide energy balance within the eight beamlines less than 10% (root-mean-square) for shots varying from 0.5 to 4 kJ (1053 nm) per beamline. The LPSM has been a crucial tool in the commissioning of the TIL.

A method of single longitudinal mode (SLM) TEA CO2 laser output by inserting a Fabry-Pérot etalon into the three-mirror cavity is presented. The output characteritics are calculated. SLM tunable TEA CO2 laser is designed and demonstrated, and tunable SLM laser output is realized. The energy over 200 mJ with pulse width of 150 ns is achieved for 9P(16) spectral line at 5 Hz repitition.

Characteristics of Er level structure and laser rate equation of an Er3+:YAG four-level system are analyzed. In the laser system, dual-lamp laser, double-elliptical cavity and spike pulse discharge are used to increase pump rate. Through increasing reflectivity of laser cavity and decreasing laser threshold Er3+:YAG laser can output 2.94 μm high-repetition-rate spike pulse laser. In order to eliminate the influence of heat effect, high-tension and high-speed laminar flow cooling technology is adopted. 2.94 μm Er3+:YAG laser with repetition rate of 40 Hz and single pulse energy of 0.5 J is achieved.

It is found that the Er3+ doped fiber laser is in pulsed state when it is phase modulated at a low frequency. A pigtailed LiNbO3 phase modulator driven by a commercial signal generator was inserted into the fiber laser cavity, regular pulses were achieved in certain conditions and other phenomena such as the change of the laser spectrum were observed. The pulse had a repetition rate from several tens of kHz to several hundreds of kHz. Analysis results have shown that it is hard to be explained by the traditional theories such as Q-switched and mode-locking theory. The mechanism of these phenomena is discussed briefly. Based on the investigation of the relationship between phase modulation and relaxation oscillation, the phase modulation and relaxation oscillation are phenomenologically considered as the reason of the pulsed laser.

A reasonable theory is proposed to explain the mechanism of the pulse phenomena in the intra cavity phase modulated all-fiber laser. Based on the self-pulsing theory in fiber laser and the spatial-coupling model in solid state laser, the physical mechanism of pulsed laser generation is investigated and explained. It is hypothesized that there are two perpendicular polarization models in the fiber laser, which are coupled with the spatial-coupling model as the solid state laser theory described. As the phase modulation induces timely change of phase difference between the two coupled perpendicular polarization models, the coupling of the two modes also changes and the pulsed laser is generated. Based on these two hypotheses, a mathematic model was established and qualitative investigation has been done. Simulative analysis a show that the theory agrees well with the experiments.

High brightness is an important direction of development of laser. How to improve the average brightness of laser by the prevailing digital technology is discussed. Based on the analysis of the influencing factors of average brightness, eight projects for improving brightness are compared and analyzed, and the best way for digital high average brightness laser (DHABL) with the coherent beam combination of chains of master oscillator power-amplifier (MOPA) is chosen. The concept and the project of DHABL are presented.

The design, key technique and manufacture of Hawkeye series external cavity diode laser (ECDL) are introduced. Primary characteristic parameters are explained and some pictures of the laser are shown. This product has long term stability and the temperature drift is less than 1 mK. The production process and technique are relatively simple. These performances have achieved the level of similar products abroad.

By use of second harmonic generation effect of BIBO (BiB3O6) crystal, laser at 846 nm produced by diode laser is translated into blue light at 423 nm. Calcium atomic beam is emitted from the vaccum Calcium oven when heated up to about 600 ℃. By illuminating the 423 nm laser onto the Calcium atomic beam perpendicularly, fluorescence spectrum of the Calcium beam is obtained with photoelectric detector. The full width at half maximum is about 100 MHz.

In0.53Ga0.39Al0.08As/InxGa1-xAs0.9Sb0.1 quantum well band structure has been calculated with the effective-mass model and 4×4 Luttinger-Kohn Hamiltonian matrix method. The relations of C1-HH1 transition wavelength versus In composition and well width have been obtained and discussed. Mechanical equilibrium model has been used to calculate the critical thickness for the strain material system. It is concluded that by appropriate structure design and adjustment of composition and quantum well parameters, the InP based InGaAlAs/InGaAsSb strained laser system can readily realize laser radiation in the wavelength range of 1.6～2.5 μm.

To meet the requirement of high precision power control of semiconductor laser used in fiber communication, the principles of semiconductor laser and photodiode were studied throughly with regard to the internal structure and power characteristics of semiconductor laser. According to the performances of LD and PD in practice, the method of power control with high precision was proposed. The power control circuit of semiconductor laser using logarithmic amplifier AD8304 with wide range baseband log compression was designed. And the closed loop control circuit was analyzed in detail according to the internal structure and principle of converter AD8304. The testing result demonstrates that the module of power control can keep the laser working stably, has advantages of wide range of operation temperature, high control precision, less cost and easy integration, and can be applied in most semiconductor lasers.

Reflection retardance induced by multi-optical coatings in output mirror of an all-solid-state single frequency V-shaped 457 nm Nd:YVO4 blue laser is reported with the theory of reflection-induced retardance by Macleod. Combining with the frequency-doubling theory of elliptical Gaussian beam under the conditions of critical phase matching, especially in type Ⅰ LiB3O5 (LBO) crystal, we discussed the influence the multi-optical coatings in output mirror on polarizing characteristic of intracavity fundamental frequency light and frequency-doubling efficiency. Research indicates that when the induced angle in output mirror is less than 15°, the refection-induced retardance is less than 2°. Furthermore, in the approximations of the exact phase matching, compared with the ideal case, the frequency-doubling efficiency reduced by multi-optical coatings is not more than 6%.

A numerical model of a dual-wavelength erbium-doped fiber ring laser is presented based on the Giles' model. According to the gain and loss match condition, the mode competition of dual-wavelength of 1550 nm and 1555 nm is analyzed. Numerical results show that even tiny changes in loss spectrum have great impact on the process of mode competition. Output powers of dual wavelength are equal when loss maches gain. However, random loss perturbation of 0.1 dB will result in the relative output power fluctuations of 1550 nm and 1555 nm up to 9.59% and 9.52%, respectively. One mode is enhanced and the other is eliminated when a long-term loss bias is larger than 0.05 dB.

To study high precision external modulation characteristics of high speed 1550 nm microwave fiber link, the relation of output power, threshold current and temperature is disucssed based on the physical model of multiple quantum well-distributed feedback (MQW-DFB) laser diode (LD). A corresponding power and temperature control circuit is set up to ensure the output optical power fluctuation within ±0.005 dB and the modulated output with 0.5 nm of 3 dB spectrum width. Its side modes are planar and the side mode suppression ratio is more than 30 dB. In addition, the automatic gain control circuit and accessional phase modulation circuit are designed in order to control light power on the stage of external modulation. Experimental results shows that the external modulation microwave fiber link system composed 1550 nm MQW-DFB laser diode and corresponding driving circuits can effectively improve output light power stability of light emitting module. It overcomes the disadvantages of light spectrum expansion and unstable optical extinction ratio due to direct modulation and realizes fiber transmission of microwave signal with high linearity and low distortion.

Coupled laser array, which realizes phase locking of elementary lasers with evanescent waves coupling, is a promising scheme to realize coherent beam combination. To reveal the stability of the phase-locked state in the array, the influence of the frequency drift on the phase dynamics of the two-coupled-laser array is researched. It is demonstrated that the frequency drift will break up the phase-locked state of the laser array and induce the spatial instability of the far-field intensity due to phase noise. It is also found that although the evanescent coupling between elementary lasers can restrain these effects to some extent, the restrainability is too limited to be effective when the frequency drift is relatively strong. It is suggested that some anti-jamming protections should be applied to the array, especially in the atrocious environment. Furthermore, the phase-locked state of the array is more sensitive to the low-frequency component of the frequency drift. Therefore, the protections should pay more attention to the low-frequency jamming.

A novel technique of optimizing chirped mirrors is proposed. Simulation demonstrates that the residual group delay dispersion ripples of two matched chirped mirrors is less than 10 fs2 over the wavelength range of 700～1050 nm and that of three matched chirped mirrors is less than 15 fs2 over the same range. These kinds of chirped mirrors have precisely controlled group delay dispersion, which plays a critical role in the generation of ultrashort pulses and compression of few-cycle to monocycle femtosecond pulses.

Beam quality control is the most important segment in high power solid state laser facility construction, for the rigid requirement of precise physics experiments and the operation safety of laser facility in high capacity. The 3ω optics system converts the 1ω beams to the third harmonic, focuses them onto the target and is an important segment influencing beam quality. Based on the B-T theory, increase of beam modulation in 3ω optics was derived under the condition of nonlinear propagation. By the medium-high phase plate constructed according to the surface profile of typical KDP crystals, influence of ∑B3ω on beam near-field quality was investigated. The results show that the fastest increasing frequency and the corresponding fastest increasing factor in 3ω optics system are triple of those of 1ω system, and periods of spatial frequency between 0.1 mm and 1 mm increase fastest. The root-mean-error (RMS) of medium-high frequency aberration has to be less than 1.6 nm to acquire ∑B3ω of 1.5 and 3ω near-field contrast below 1.15.

For a radio-frequency (RF) excited slab CO2 laser the far-field spot is 0 form, the near-field profile is near a line form. The laser beam is more divergent in a certain direction on a plane perpendicular to the transmission direction, and cannot be used in laser material processing. According to the laser power and laser beam dimension, the near TEM00 mode with 6 mm diameter of a circular laser beam is got in a 200 W laser as well as the low order mode with 10 mm diameter of a circular laser beam in a 500 W laser, using defferent combination of circular cylindrical mirrors, diaphragm and beam-expanding telescope. The laser can be used in laser material processing.

Online calibration of wave-front sensor's reference plate and problem of pre-corrected laser being clipped at pinhole are two key factors when adaptive optics system is used in high power solid-state facility. The advantages and disadvantages of the two calibration methods have been researched, and calibration methods and results are chosen by considering adaptive optics system controlling object. For the pre-compensation program, the main factors of laser clipping problem have been researched, and the problem can be solved by adaptive optics system control model and laser system operation process. Satisfying experimental result is achieved.

Under the study on rod Nd-glasses heat-capacity laser thermal lensing,the general expressions of the thermal focus length are derived. The self-adjusting compensation is presented in theory. Using the characteristic of Nd-glasses, self-adjusting compensation system for thermal lens focus is designed to weaken the effect of the thermal lens on light pumping glasses heat-capacity lasers. Thus, a stable output spot radius can be achieved while the thermal lens focus varies in a broad range. In order to study the effect of heat-capacity laser thermal lensing, a wavefront curvature sensor comprising a phase defocus grating is used to measure the focus length. The result indicates that the heat exchange sets up a heat balance in about 20 s after pumping. With the increases of the numbers of pumping pulses, the thermal focus length deceases.

Coherent combining technology is an effect method to achieve huge amounts of fiber laser coherent combination, and phase-locking is the key.Two phase-locking methods, heterodyne detection and multi-dithering technique, for master oscillator power amplifier (MOPA) are compared, and a new phase-locking method is proposed based on multi-dithering phase-locked method. This method enlarges the number of optical beams and makes the experiment easier. Through simulation by Matlab solfware, we find that the root-mean-square (RMS) phase error of 64 beams combiniation is less than 0.08λ with the new method, while the RMS phase error of 30 beams combination is 0.15λ with the multi-dithering technique.

Mode filtering by gain structure in multicore fiber laser is studied. The supermode distribution of a 7-core fiber laser is calculated by the vector coupled-mode theory, and gain coefficients for different supermodes in different power-levels are calculated. It is shown that in a low power level, gain coefficients for different supermodes almost equal to each other, the far-field laser profile emitted from the multicore fiber laser will give mix-mode character. When the laser output power is in a higher level, the gain coefficient for the in-phase mode is the largest among all the supermodes, which will dominate the mode competition. The far-field laser profile will show in-phase mode character. The validity for the mode filtering by gain structure is discussed.

Load capability has become the bottle-neck in the progress of high-power solid-state laser facility, the research of which is mainly focusing on the interaction process of laser near-field and optics. Evolvement of experimental near-field intensity with the rise of laser intensity in a multiple-pass amplification laser driver has been researched by power spectral density (PSD). It is shown that, the near-field show obvious frequency-related characteristics, and two-dimensional PSD of near-field is isotropic. Modulation of near-field is due to small-scale self-focusing in high-intensity state. Growth of spatial frequency from PSD curve is mainly in the spatial frequency band, which is decided by the cut-off frequency of spatial filter pinhole.

The former laser systems are complex to realize multiple transverse modes. Only the fundamental mode and low-order modes can be generated, and the high-order modes are hard to be generated. Furthermore, the changing process of one frequency restraining another in mode competition is hard to be observed. A novel synthetical demonstration system of laser principle is presented based on a cat-eye cavity laser and the frequency splitting technology. In the system, a cat-eye retroreflector is treated as the cavity mirror of a He-Ne laser. More than ten typical transverse modes including fundamental mode, low-order modes, and high-order modes can be generated by adjusting the distance between two lenses in the retroreflector. In addition, more experiments of fundamental laser characteristics, such as longitudinal mode, laser polarization, and lasing bandwidth, are also carried out. In the condition of fundamental transverse mode, with a quartz crystal plate put in the cavity, laser frequency splitting and frequency difference adjusting can be achieved. Based on it, the dynamic process of mode competition can be observed.

A simplified version together with a double-array 1D atomic hydrogen cluster model is presented for simulating cluster dynamics when exposed to intense light. The computed maximum kinetic energy and cation number distributions were in fair agreement with numerical results and experimental observations. An expression for determining the abundance variation of ionized cations with exciting laser intensity was proposed from which the threshold laser intensity of cluster Coulomb explosion could be extracted.

The evolution and interaction of picosecond dark pulses with finite-width were discussed by solving the nonlinear Schrdinger equation with variable coefficients numerically. The results show that, periodic regeneration effect of dark solitons stably exists in the distributed system. And periodic regeneration of dark solitons is not influenced by the interaction. Further simulations indicate that this effect is less sensitive to both loss and finite perturbations, such as white noise. This reveals that this periodic regeneration effect is stable.

To solve the forming difficulty in the microforming microparts made of hard-to-deform material, a novel approach about micro plastic forming based on laser-assisted double-sided heating method has been presented. Numerical simulations are completed and analyzed using a finite element method (FEM) softwave, ABAQUS to study the temperature field distributions and the stress distributions of the billet and the effect of laser-assisted heating on the characteristics of microforming. Accordingly, the coupled thermo-mechanical finite element model of cylinder billet is developed.The results show that an appropriate temperature field for microforming can be established using the laser-heating method, resulting in the decrease of microforming force and the improvement of formability of microforming material. The novel method will extend the applications of microforming.

The finite element method is introduced to study the three-dimensional temperature fields for bilayer structure of diamond/ZnSe substrate films irradiated by laser-induced transient surface grating. The temperature fields are compared for different thickness of diamond film. It is shown that the thickness of the diamond films has great influence on the temperature distribution of the films. With the thickness increase of the diamond film,the peak of temperature field in the sample increases and the twice heating becomes more obvious.

The cryagenic radiometer traceability method of the 1.3 μm/1.5 μm fiber laser power is reported. The traditional method to trace to the absolute radiometer is analyzed. The trap detector is calibrated against the cryogenic radiometer at wavelength of 633 nm, and use to deliver quantity value to trap quantity detector, and than the InGaAs detector is calibrated by the pyroelectric radiometer with power-stablized laser source at wavelengths of 1310 nm and 1550 nm and used to measure fiber laser power. The measurement result shows that with this traceability method, the standard deviations of the optical power correction coefficients at wavelengths of 1310 nm and 1550 nm are 0.0011 and 0.0007, respectively, and the uncertainty of measurement is better than 0.6％ (k=2). This method can keep the consistence of quantity value decline measurement uncertainty and increase accuracy of quantity value delivery.

From the spatial structure of the grating, the amplitude distribution ［(θi)］ of not-even grating and the characteristic of light intensity ［I(θi)］ were deduced with the formula of Fresnel diffraction. The curve of I(θi)～θi was plotted by using the Maple procedure and the diffraction characteristics of not-even grating was obtained. The distribution of (θ) and I(θ) of the one-dimensional (D) transmission surface grating is correlated not only to grating constant but also to each single gap width. The result supplements the property of the flat surface grating differaction, and provides with theoratical basis to adjust,design, develop, and test the spatial structure of grating.

A system for measuring high reflectivity of the coating at IR wavelength (3.6 μm) by cavity ring-down spectroscopy (CRDS) with straight cavity and fold cavity has been set up. The measurement precision approximates 10-4. It can be used to study high reflective IR coating on mirrors. Three kinds of coatings designed for cavity mirrors have been measured with the straight cavity CRDS, and a pair of cavity mirrors have been employed in experiment. Reflectivities of mirrors deposited by YbF3/ZnS,YbF3 /ZnSe and Ag added with protective coating were measured. The reflectivity of the dielectric coating can reach R>0.9990, and the reflectivity of YbF3 /ZnSe on silica substrate is 0.9996 at 3.6 μm.

The reflected tensile wave is a main damage mode of materials failure in laser shock processing. The shock test of Al2O3 ceramic was carried on using high power Ndglass pulse laser for further analyzing shock performance of ceramic materials and controlling the demage to improve its toughness. The different damage mode appeared through sticking film on the back of the ceramics. It can be illuminated that the energy of reflected wave is reduced to 40% of that before sticked, and the baleful rupture caused by tensile wave is greatly depressed by lessening reflected energy.

The characteristics of nonlinear transmission of shaped pulse through the stacking 32 linearly chirped Gaussian pulses in single mode fiber were analyzed by solving the generalized nonlinear Schrdinger equation numerically. The simulating results indicate that after 50 m transmission in a single mode fiber, the duration and the envelope shape of the stacking chirped pulses have almost no change. The nonlinear effects, such as self-phase modulation and intrapulse Raman scattering, impact seriously on the spectral domain characteristics of the pulse, the spectral width is broaden about 40 THz and the center angle-frequency is downshift about 10 THz. The self-steepening effect and the third order dispersion affect the transmission characteristics little.

The technique of computer-generated holography (CGH) is introduced into the experimental system on laser ultrasonic non-destructive evaluation (NDE). This system employs a direct-search algorithm to generate the hologram and further reconstructs the hologram via aliquid crystal spatial light modulator. Specifically, a generation and reconstruction method is applied to help the spatial modulation of the laser pulse to excite narrow-band ultrasound. Due to the robusticity of the algorithm and the flexibility of the reconstruction method, this method can simplify the laser ultrasonic setup and substantially shorten the experiment period. Thus there will be a variety of applications for this system in the fields of NDE.

3D LIDAR in China has a huge market, but foreign commercial 3D LIDAR is very expensive. So a 360° continuous scanning, portable 3D LIDAR system is developed. A 2D laser scanner (SICK LMS200) is selected to combine with an additional step drive to reach a 3D sensor. The sources of systemic errors are analyzed, a method of error correction is proposed, and the accurate calculation formulas of 3D coordinates are given. The experimental results show that the system has higher measuring accuracy and data quality. The maximum range of the system is 80 m, measurement accuracy can achieve 6 mm. It can collect 7256 points in a second to meet the needs of fast capturing 3D data from indoor and outdoor scene, and then its cost is only 4 times lower than that of current commercial 3D laser scanners. It is easy to carry for small size and light weight.

The laser tailor welding craftwork was analyzed. The effects of laser power, welding speed and defocus on welding quality for high-power solid-state laser were studied, and the variation laws was plotted. The laser welding craftwork for common blanks of full thickness series in automotive industry was studdied, and the optimal welding craftwork for full automatic laser tailor welding line was obtained with the method of interative optimalization.

A new technique base on femtosecond laser local field enhancement effect is proposed. Nanomachining of thin gold films was accomplished by coupling 800 nm femtosecond laser radiation with an atomic froce microscope Si3N4 tip in ambient air by the local field enhancement effect. Possible factors affecting this process are discussed like the speed of the fabrication and the laser fluence. At last we get the high spatial resolution of (～10 nm) (not possible with standard nanomachining techniques). The presented process provides an intriguing means for massive nanofabrication due to the flexibility in the substrate material selection and easy lithograph of complex pattern.