We have built a three-stage Ti:sapphire laser system at CAEP which could deliver 5-TW, 30-TW and 286-TW pulses to the corresponding target chambers for diverse applications with innovative high-power Ti:sapphire crystal amplifiers. Pulse durations of 30fs have been obtained by installing an acousto-optic programmable dispersive filter (AOPDF) before the stretcher to compensate for the spectral gain narrowing. By taking a number of advanced measures for spatial beam control, near-diffraction limited focal spots (FWHM) have been obtained which, to our knowledge, are the best far fields ever measured for the existing high-power Ti:sapphire laser systems without deformable mirror correction. Focused laser intensity is about 10²¹W/cm² measured with an f/1.7 OAP. The laser system has the potential to operate at 500TW and even higher and laser intensities of 10²²W/cm² are expected with deformable mirror for wavefront correction and small f-number fine OAP for tighter focus added to the system in the near future.

We are now constructing a technical integration experiment line (TIL) at CAEP, which is the prototype facility of Shenguang III laser fusion driver. Currently, many important results have been obtained on the first integrated beam line, which established a sound foundation for Shenguang III engineering design.

The technical integration line (TIL), which is the full scale prototype for Shengguang-III laser facility (SG-III), now under construction at CAEP, will contain a neodymium glass laser system with more than 70 large (40-100 cm) optical components. Reflections from these surfaces (so-called ghost reflections) are numerous and extensive computation has been required to track them in the TIL optical system. The tremendous number of ghost paths requires a visualization method that allows overlapping ghosts on optics, and then sums them up to illustrate its potential damage on critical surfaces. Therefore, how to make an effective identification and visualization of multi-order "ghost" has been a major part of the optical design effort. This paper addresses the following aspects of TIL ghost analysis: 1, comparison of several methods for ghost energy simulation. 2, some techniques for visualization of complex optical systems in 3D space including mirrors and pinholes. 3, attempts at visualizing “ghost energy” distribution near some critical surfaces so as to provide detailed references for mitigation of ghost caused damage.

Diffraction components are applied in high power laser systems for beam shaping and harmonic separation. Because of the multi-order diffraction and multi-reflection to high power laser, the distributions of stray light energy and ghosts are much more completed in the systems than in conventional optical systems. In this paper a data structure of tree is presented for describing the stray light caused by multi-order diffraction and multi-reflection. All the nodes of the tree can be dynamically saved and be deleted, and the intermediate results those are useful for the next calculation step can be reserved in RAM. Using this method the multiple repeated calculations in conventional stray light analysis methods such as Monte Carlo technique are avoided and the analysis time is reduced. According to the paraxial tracing, the software which can be used for analyzing the stray light caused by multi-order diffraction and multi-reflection in high power laser systems is developed and the stray light tree of a laser system based on paraxial tracing is built. As shown by the example that this algorithm is available for quickly analyzing stray light in the systems including diffraction components, and the ghost positions with energy descriptions can be given by the software. The ghosts those are harmful to the important components will be picked.

In conceptual design of the prototype for SG-III facility, a full aperture electro-optical switch was placed between the cavity mirror and the main amplifier to isolate the reflected beams. The beam on the cavity mirror is 240mm×240mm square. Pockells cells of conversional design with coaxial ring electrodes can not scale to such large square aperture. In the 1980s, a plasma electrode Pockels cell (PEPC) concept was invented at LLNL. It uses transparent plasma electrode formed through gas discharge as the electrodes to apply the voltage across switching crystal to rotate the polarization of a transmitted laser beam. And it can be scaled to large aperture with thin crystal. So the switch which would be used in SG-III is based on this technology. The technical integration line as a prototype of SG-III laser is actually a 4×2 beam bundle. And the full aperture optical switch is mechanically designed four apertures as a removable unit, and electrically two 2×1 PEPC putting together. So we built a 2×1 PEPC to develop the technology first. The 2×1 PEPC is a sandwich structure made of an insulating mid plane between a pair of plasma chambers. The frame of both plasma chambers are machining in duralumin. Each chamber is installed with a planar magnetic cathode and four segments spherical anodes made from stainless steel. The cathode and anode are insulated from the housing with a special shell made from plastic, and plasma is insulated from the housing by an 80-μm-thick anodic coating on the duralumin. The two plasma chambers are separated by a mid plane of glass frame with two square holes. The two holes are filled by two electro-optical crystals with a 240-mm square aperture. With the optimized operating pressure and the electrical parameters, a very good homogeneity and low resistivity plasma electrode is obtained. Finally we tested its switching performance to simulate the case that it will be used in the SG-III prototype facility. It works with a quarter wave delay voltage and the laser beam passes through PEPC twice. The average switching efficiency across the entire aperture is greater than 98.6%, the rising time of the switch is about 83ns, and the transmission of the switch is 86%.

In this paper we find the spectral bandwidth is more important than the duration of pulse for analyzing the evolution of ultrashort laser pulses. A general novel (3+1) dimensional propagation equation first-order in the propagation coordinate is derived, which is independent of the envelope and carrier frequency. This equation provide an accurate description of the evolution of the ultrashort pulsed beam through the dispersive nonlinear medium, with the numerical value of the bandwidth being bigger than the carrier frequency and considering the true frequency. A family of exact solutions of the novel linear (3+1) dimensional equation in the dispersive medium has been derived, which represents the pulse with ultrawide bandwidth evolving due to gain (losses), dispersion, and diffraction. The use of the novel dispersive and loss coefficients is analyzed.

Pico-second solid-state lasers with multi-watt average power and multi-kilowatt peak power are required for numerous applications such as UV generation and pumping of optical parametric oscillators for RGB laser TV display. In the past few years laser diode bars as pump source with continue output power of hundreds watts or more have become commercially available. LD side pumping YAG laser module can be used to generate high reputation mode locked output pulse with SESAM (Semiconductor Saturable Absorber Mirror) as an end cavity mirror. In this paper, we demonstrate an all solid-state mode-locked YAG laser with three-mirror folded cavity with a SESAM mirror, 80MHz pulse rate, about 10ps pulse width, and 2W 1064 nm output power. Thermal effect of laser rod, and polarization of intra-cavity beam are considered in laser cavity design. The enhancement of laser performance and decreasing Q switching effect are discussed. Further investigation is greatly needed.

The study of long-range propagation of ps UV laser pulses in atmosphere and the beam profile spatial evolution is presented. The laser used in the experiment is a dye-KrF hybrid laser with the wavelength of 248 nm, maximum pulse energy of 140 mJ and pulse width of less than 10 ps. Measurement of spatial profile of laser beam and the plasma column produced of along the propagation direction verify that the filamentation of self-guiding is 2.6 m and the diameter of the self-guiding beam is 160 μm for the incident beam energy of 40 mJ. The electron density in the self-guiding column is derived to be several times of 10¹⁵ cm^-3 level using a weakly ionized model.

It is being clarified why the observations of plane wave geometry interaction within the skin depth of a laser irradiated target are very unique exceptions from the broad stream of the usual experiments of laser plasma interaction. This permits a much more simplified description by plane wave interaction theory for laser pulses of about ps or shorter duration and powers above TW and simplifies computations in contrast to the usual cases with relativistic self-focusing. After establishing theoretically and experimentally the generation of highly directed plasma blocks with ion current densities above 10¹⁰ A/cm² moving against the laser light or into the target, applications for laser fusion, and a completely new improvement of ion sources for the next generation of accelerators are discussed.

We present a conceptual design of multi-PW ultrashort laser system based on existing large-aperture Nd:glass laser facility. Compared with current PW laser, innovative technologies are adopted in the design, which includes large-aperture OPA to generate 10mJ femtosecond laser at 1 μmicron directly, high energy OPCPA preamplifier up to 1 J-level and chirped pulse shaping by AOPDF. To simulate the multi-PW CPA precisely, we build up an amplification model that can treat either homogenous broadening or inhomogenous gain media. As a first phase of our multi-PW laser, we are now constructing an ultrashort laser system that can produce pulse energy > 100 J with pulse duration of 350 fs.

We study the phenomena of self-focusing and self-defocusing of an optical beam in a nonlinear negative-refractive-index material (NRM). It is shown that an optical beam propagating in NRM experiences self-focusing and self-defocusing for negative and positive nonlinear refractive index respectively. The critical power for self-focusing is the same as that in a conventional nonlinear positive-refractive-index material. Further, we show by numerical simulations that the nonlinear NRM can be used to compensate for self-focusing in the propagation of high power lasers in conventional nonlinear positive-refractive-index medium. The modulation generated by self-focusing in nonlinear positive-refractive-index medium can be reduced drastically by inserting a piece of nonlinear NRM.

We report on a numerical investigation of propagation property of high-power broadband laser beam in free space. We use Hankel transformation to solve Helmholtz equation numerically in the frequency domain. The modulation property of the broadband laser beam propagating in the Fresnel diffraction region is disclosed. It is found that the number of diffractive modulation rings equals to half the Fresnel number corresponding to the central wavelength of the broadband laser beam. The intensity modulation contrast of the broadband laser beam is smaller than that of monochromatic laser beam, suggesting that the broadband laser beam can suppress the harmful effect of near-field diffraction to some extent. Furthermore, it is demonstrated that the uniformity of near-field diffraction profile is determined by Fresnel number and bandwidth of the broadband beam.

We overview our recent progress on developing nonlinear quadratic technologies for femtosecond lasers at 1 μmicron. Quadratic optical nonlinearity χ⁽²⁾ can be exploited in femtosecond lasers and regarded as a significant new degree of freedom for the design of short-pulse sources.

We report on the theoretical investigation of the amplification of highly chirped pulse with ultrabroad bandwidth. Based on the analysis of the properties of the pulse with a very big chirp, we build a theoretical model for the amplification of highly chirped pulse. The model includes the effects of homogeneous and inhomogeneous broadening. Based on our model, the difference between the inhomogeneously and homogeneously broadening amplification is identified by numerical simulations. We believe that the obtained model can be used to evaluate the laser-performance, and optimize the laser design.

The wave equation of light beam propagation was written in the form of an axial-coordinate-dependent Schrodinger equation, and the expectation value of a dynamical variable and the ABCD law were discussed by use of quantum mechanics approach. With the in-depth study of this theory, it has extended from the ABCD system to the effective ABCD system etc. All of the works are introduced in detail to interest others in this theory.

The laser induced ionization of ambient air is studied experimentally with laser pulses whose durations range from 50 fs up to 10 ps at 800 nm. It is found that the minimum pulse energy for detectable air ionization follows the scaling law of ε_th varies direct as t_p^x, with 0.23 < x < 0.5, and x tends to rise for longer pulses within the range of 50 fs - 500 fs. For laser pulses from 0.7 ps to 10 ps, however, x is approximately equal to 0.8. The dependence of the critical intensity for air ionization on the beam spot size is also examined with a variety of focused laser beam spot sizes in the experiments.

Thermal effects present a major challenge to scaling of solid-state laser to high-average power. When using a thin laser crystal disk with a nearly flat-top pump profile, the heat flux can be considered to be one-dimensional. This results in a homogeneous temperature and stress profile within the laser medium leading to reduction of thermal effects. The pump profile is the main factor that may affect the homogeneous temperature profile, but some other factors may affect the temperature homogeneity, such as the cooling dimension and the ratio of the pump area to the thickness of the disk. These factors are analyzed and a good design is made. An average output power of more than 120W is obtained from one single disk and that of 216W from two disks.

A novel high average power double slab laser with hybrid resonator is presented. By analyzing and simulating thermal distribution of the face-pumped slab medium, it is found that the thermal distortion of wave front caused by the non-uniform temperature distribution of the laser gain media can be self-corrected in this structure. According to the analysis of the slab thermal distribution, a hybrid resonator is presented. Using a plane-wave or k-space expansion together with the fast Fourier transform, mode patterns, power outputs from the laser are calculated. Far-field characteristic and beam quality of these modes are discussed. And besides, by comparing the properties of off-axis hybrid resonator with the on-axis hybrid resonator's, the off-axis hybrid resonator can produce better quality beam.

A dual-wave Quasi-CW Nd:YAG laser has been demonstrated at the wavelengths of 1319 nm and 660nm. The radiation energy level of the 1319nm transition was analyzed. The critical technology of restraining resonance of 1064nm so as to improve that of 660nm was discussed. Sophisticated optical coating and cavity structure was studied. And a maximum CW Output power of 43W at 1319nm was acquired. Based 1319nm laser, an intracavity frequency-doubling laser of 660nm was also demonstrated by using KTP crystal and an acousto-optically Q-switch. And a Quasi-CW red light output power of 2W at 660nm was acquired, accordingly, dual-wave output was realized.

We report that the phase of backward Stokes waves can be independently controlled, which is necessary for a beam combination laser using stimulated Brillouin scattering-phase conjugate mirrors (SBS-PCM). The phase control is achieved by a self-generated density modulation without seeding the Stokes beam. Theoretical analysis shows that the phase fluctuation is mainly due to the pump energy fluctuation and is inversely proportional to the pump energy. We have achieved that the relative phase difference between two Stokes waves via SBS is smaller than λ/4 for all the pump pulses.

An alignment-free directional prism resonator that ensures the laser TEM₀₀ mode with thermal stability in a certain range is designed by using g* parameter equivalent method. The output of all solid state laser is about of 150mJ, and the beam divergence is of 3mrad with 20Hz repetition rate, moreover, when the laser operates from 10 to 30Hz, the beam divergence is steady. This laser meets the needs of special engineering application.

In this paper, we report a high power of cryogenic cooling Tm(8 at %), Ho(1.4 at %):YLF dual end pumped by two fiber coupled laser diodes at 792nm. Each pumping laser head delivers 15W power in an inner fiber core area of 0.4mm and numerical number of 0.3. The highest continuous-wave (cw) power of 10.2W at 2.051μm is attained under pumping power of 30W, corresponding to optical-optical conversion efficiency of 33%, and the slope efficiency is greater than 36%. The maximum acousto-optical Q-switched quasi-continuous wave output power is 9.2 W at pulse repetition frequency of 10kHz, corresponding to greater than 90% extraction efficiency in the full-width half-maximum pulse width of 34ns.

2.1μm solid state laser operating at room temperature is a very useful laser source for optical communication, medical care, air pollution monitoring and Lidar, etc. It is eye-safe. It is also a very ideal pump source for optic parametric oscillator to get 3μm -5μm radiation. In order to further explore its potential applications, higher peak power and shorter pulse width are very desirable. Q-switching the laser is a most practical way to realize those goals. Among the most common used Q-switching techniques, mechanical Q-switching is not preferred due to that it involves use of a rotating motor, which has lower life time and causes undesirable vibration. E-O Q-switch material in this wavelength range is very expensive and quite susceptible to optical damage. On the other hand, low OH concentration quartz material exhibits very low absorption at the 2.1μm. The Cr:Tm:Ho:YAG 2.1μm laser has undesirable lower gain from the laser efficiency point of view, but offers a feasibility of using the A-O device for the Q-switching even the laser is pulse pumped. The Cr:Tm:Ho:YAG 2.1μm laser is a so called quasi-three level laser, which is characterized as having a higher threshold and lower gain. This study is focused on the optimization of the laser resonator design and the A-O Q-switch design for a higher laser peak power and shorter pulse width. Factors considered in the study include AO Q-switch’s RF frequency, modulation depth, active aperture, resonator length, resonator loss and pumping design, etc. Experiment results are compared with the Q-switched quasi-three level laser model. Final result of the Q-switched 2.1μm laser after preliminary optimization will be presented.

This paper report the A-O Q-switched LD end pumped 8% Tm, 1.4%Ho:YLF laser. The fiber-coupled pump laser deliver maximum 15W around 792nm At 10 KHz pulse repetition frequencies (PRF), The average output power of 4.1 W, the pulse width of 32ns and peak power of 0.012MW at 2.05um were achieved. The pulse fluctuation is less than ± 2%. The pulse amplitude instability at last higher rate equation was analyzed.

The optical characteristic of Nd:YAG ceramic was introduced, and a LD pumped high efficiency Nd:YAG ceramic laser was demonstrated. The laser threshold is 48mW with R=97% output coupler. With 2W LD pumping, 812mW CW laser output at 1064 nm has been obtained, and the corresponding optical-to-optical efficiency is as high as 45.6%. A LD pumped high efficiency high repetition rate A-O Q-switched Nd:YAG ceramic laser was also demonstrated. With a 2W LD pumping, the obtained narrowest pulse width, highest peak power and highest energy per pulse are 16.4ns, 2.46kW and 40.5μJ, respectively. The experimental study about the influence of repetition rate on the performance of A-O Q-switched pulse laser was emphasized, and the experiment results were analyzed and discussed.

In this paper, the absorption and Fluorescence spectra of Cr⁴⁺,Nd³⁺:GGG (Cr,Nd:GGG) crystal, Nd:GGG crystal and Cr⁴⁺:GGG crystal are reported. In the absorption spectra there are big absorption bands at 400 and 520nm, which correspond to the ⁴A₂→⁴T₁ and ⁴A₂→⁴T₂ transitions. The luminescent spectra of Cr,Nd:GGG and Nd:GGG show that the luminescent center of Cr,Nd:GGG is at 1.062um, but the intensity is 6 times lower than that of Nd:GGG. The luminescent lifetimes of Cr,Nd:GGG is shorter than that of Nd:GGG. These may be caused by the existence of ground state absorption of Cr⁴⁺ which quenches the Nd³⁺ emission intensity. These Cr,Nd:GGG crystals may be potential materials for compact, efficient, high stability diode- laser-pumped passive Q-switched solid state laser.

We report on the experimental studies of a diode-end-pumped CW Nd:GdVO₄ laser. CW output power of 19.8 W at 1064 nm and a slope efficiency of 58.5% were obtained under the pump power of 39.5 W. The beam quality M² at maximum output power was measured to be around 2.62. The thermal focal length in Nd:GdVO₄ crystal under the pump power from 22 W to 40.6 W was measured.

In this paper, we report a high efficient and high power continuous wave diode-pumped cryogenic Tm(5% at.), Ho(0.5% at.):GdVO₄ laser. One pumping source of Tm,Ho:GdVO₄ laser is a fiber-coupled laser diode with fiber core diameter of 0.4 mm and numerical aperture (N. A.) of 0.3, supplying 14.8 W power at 793.6 nm. Another fiber-coupled LD radiation wavelength is centered at 805 nm with 0.22 N.A. and the same core diameter delivering power of greater than 30 W. For input pump power of 13.6 W at 794.2nm, the maximum output power of 4.2W, optical-to-optical conversion efficiency of 31% and slope efficiency 38% have been attained at 2.048 μm. The maximum cw power of 7.9-W is achieved by 805 nm LD under power of 26 W, corresponding to 40% optical-optical conversion efficiency relative to absorbed pumping power, which is close to quantum limited efficiency of 2 μm laser.

The stabilization and modes of a high-power intracavity frequency-doubled Nd:YAG laser are numerically analyzed, the great influence of frequency-doubler’s thermal lensing on the stabilization and modes of this laser is demonstrated, and a compensating method is developed. A high-power QCW 532 nm green laser has been fabricated in the experiment, with a KTP crystal (θ=90°, φ=24.7°, 6×6×9.2mm, cut for high-temperature (80°C) application) as frequency-doubler. With the KTP crystal warmed up to 48.8°C and resonator parameters adjusted optimum according to the calculated thermal focal length of KTP crystal, a maximum 110W green laser is generated at 10.6kHz repetition rate, and its pulse width is 142ns, instability 2%, and optical-to-optical efficiency 11%.

We reported phase mismatch compensation of second harmonic generation with controlling boundary temperature of type-II KTP crystal in high power intracavity frequency-doubled Nd:AG laser. Thermal induced phase mismatching of the KTP crystal was analyzed theoretically by numerical computations of temperature derivative of refractive indices. The temperature gradient of the KTP crystal, phase matching angles change with difference boundary temperature of the KTP crystal, and tolerance temperature was analyzed. In the experiment, when two KTP crystals of difference type II phase matching condition (Φ=23.6°, Θ=90° at 27°C temperature, Φ=24.7°, Θ=90° at 80°C temperature) were applied to compensate the phase mismatching of the type-II KTP crystals. The maximum average 532nm output power of 85 W and 110W were generated when the boundary temperature of KTP were kept in 4°C and 48.8°C respectively. The corresponding conversion efficiency is 9.03% and 11%.

Under the condition of high power diode side pumping, thermal effect in working medium is a serious problem. Not only total pump power, but also special pump structure, such as pump geometry structure, divergence of diode laser, distance from diode to working medium will affect the result of thermal effect. In this paper, by means of computer program, we found a series of thermal effect model, by simulating the temperature transformation process and stable-state temperature distribution. Based on this, we get the theoretical results of thermal lens focus length and thermal induced bi-refraction, and compare it with the experiment results.

Solid-state heat-capacity laser (SSHCL) has been developed in recent years. One of the key features of this heat capacity approach is the inversion of the temperature profile through the medium as compared to conditions where the laser is actively cooled while lasing takes place. So the thermal effects in the active medium on the two conditions mentioned above must be different. In this paper, we mostly discuss the contribution of temperature gradients to the effect of the thermal lens in optically pumped cylindrical laser rods operated in heat capacity operation through classical thermal conductivity equation, end effects and birefringence of the material with stress from temperature gradients ignored. Expressions are derived for the focus length of thermal lensing in laser rods for single-shot and repetitively pulsed operations. Programming the computer, we respectively calculate the thermal induced refractive power of the laser rods in the heat capacity operation and on the cooling condition, and compare the double results.

The internal boundary conditions analytical model of laser heat treatment temperature field calculation results, which is validated by experiment, is used to reconstruct three dimensional temperature field distributions by DELPHI. The different lays temperature field of laser treatment is reality reappeared; it is useful to the research of laser heat treatment.

A new type of Q-switched pulsed lasers (CPQL, Controllable Passively Q-switched Laser) is presented. The laser is composite of a passively Q-switched laser with a saturable absorber and a controlling LD with a focus system. The performance of the laser output pulses, including the pulse energy, pulse width, pulse generation moment and repetition frequency, can be actively controlled by the operator with the controlling LD. The new type laser is discussed theoretically and the experiment results are present. Compare to the ordinary Q-switched laser, including passively Q-switched lasers and actively Q-switched lasers, CPQL’s have higher performance and will find important applications in many fields.

Simultaneous passive Q-Switching and mode locking at low pump power was observed in a Laser Diode (LD) pumped Nd³⁺:YVO₄-Cr⁴⁺:YAG laser, detailed studies were experimentally carried out. A fiber-coupled LD with maximum output power of 2 W is used as pump source. In a 50cm long cavity, the repetition rate of obtained mode-locking pulse train is about 300MHz, and the pulse duration was estimated to be at sub-nanosecond level. The repetition rate of the passive Q-Switched pulse train varies from 10kHz~130kHz with the increasing of the pump power. It was found that the threshold of incident pump power to generate mode-lock in such a laser is dependent on the position of Cr⁴⁺:YAG crystal inside the cavity. Select proper Cr⁴⁺:YAG as saturable absorber and optimize its position, simultaneous Q-Switching and mode-locking occurred in the Nd³⁺:YVO₄ laser at pump power as low as about 200 mW. The experimental result demonstrates the possibility of obtains ultra short optical pulse in a simple and low cost way, which is of great interest in some applications.

Based on requirement of all fiber structure, all fiber Yb-doped fiber grating laser uses double cladding fiber with Yb-doped as gain medium, uses fiber grating as resonance cavity and employs semiconductor laser as pumping source to realize the lasing based on the reverse of Yb ion. We use Bragg fiber grating as the resonance cavity of fiber laser and 970nm LD as pumping source, pump the Yb-doped double cladding fiber with circular inner-cladding. We realized 7.5W single-mode laser output, central wavelength of 1080nm, FWHM of 0.11nm under the pump power of 11.8W. Maxim conversion efficiency is 63.5% and slope efficiency of 46.4%.

Chemical oxygen-iodine laser (COIL) has a great potential for applications such as decommissioning and dismantlement (D&D) of nuclear reactor, rock destruction and removal and extraction of a natural resource (Methane hydrate) because of the unique characteristics such as power scalability, high optical beam quality and optical fiber beam. Five-kilowatt Chemical oxygen-iodine laser (COIL) test facility has been developed. The chemical efficiency of 27% has been demonstrated with a moderate beam quality for optical fiber coupling. Our research program contains conventional/ejector-COIL scheme, Jet-SOG/Mist-SOG optimization, fiber delivery and long-term operation.

An experimental investigation of a pulsed electrooptically Q-switched radio-frequency partial Z-fold waveguide CO₂ laser with two channels is presented. The heterodyne frequency stability is analyzed in theory. Q-switched pulses are obtained from the partial Z-fold channel. The peak power is 730W and the pulse width is 150 ns. CW laser can output from the single channel. The laser output directions are opposite.

In this paper, we have presented a new type of RF excited diffusively cooled all-metal slab waveguide CO₂ laser. In this laser structure, the four side walls of the slab waveguide are all made of aluminum alloy instead of ceramic and metal sandwich waveguide structure in the past technique. In our approach, a low cost of slab waveguide CO₂ laser can be achieved. By using the technique in this paper, over 100 watts of laser power has been achieved from a laser head with dimension of 150mm height, 150mm width and 450mm length, which has the slab waveguide gas discharge region of 2mm height, 20mm width and 386mm length. The electro-optic conversion efficiency is over 12%. In our experiment, a gas mixture of CO₂: N₂: He: Xe =1: 1: 3: 0.26 has been employed, and the gas pressure is in the range from 6.5 Kpa to 13.5 Kpa. The frequency of the RF power is 91.5 MHz, and the RF power is in the range from 500watts to 1000watts.

A four-stage XeCl laser system named Photons has been developed for studying laser interaction with materials. The Photons are outlined and preliminary results characterizing the system are given. The master oscillator Photon-1 can provide “seed” light with laser energy of about 40mJ, pulse duration of about 250ns and good beam quality of nearly diffraction-limited divergence angle and narrow line width less than 1 cm^-1 for whole system. The output energy of laser system of 251J has been obtained by four-stage amplification. The synchronization among five lasers is realized by the combination of low voltage timer, high voltage synchronic generators and compensated cables. The demonstration shows Photons good operation with low jitter of less than ±20ns.

We describe a 3D microprocessing for directly forming microoptics buried in a glass chip using a femtosecond (fs) laser irradiation followed by postannealing and successive chemical etching. By forming hollow internal structures with smooth surfaces inside glass, a variety of 3D microoptical components, such as micromirror, microbeam splitter, and microoptical circuit have been embedded in the glass and their optical properties were interrogated at the communication wavelength of 1550nm. The micromirror can reflected the light beam at 90 degrees by a total internal reflection with an optical loss of only 0.24dB. The 3D microoptics can then be integrated with 3D microfluidics for producing functional devices. Herein, we demonstrate the fabrication of microfluidic dye lasers and test the lasing functions. After filling the microfluidic chamber with a laser dye rhodamine 6G dissolved in ethanol and pumping the microfluidic laser by a frequency-doubled Nd:YAG laser, lasing action was confirmed by analyzing the emission spectra at different pumping powers. Furthermore, use of such a true 3D processing also enables fabrication of devices with multi-layered configuration. By serially embedding two microfluidic chambers in the glass, we built a microfluidic twin-laser which produces array of simultaneous two laser emissions using one pumping laser. The integration of 3D microoptics and microfluidics into the single glass chips opens up the possibility of automatic manufacture of hybrid devices for photonic applications.

We study the density response function of a semiconductor heterostructure under a quantising magnetic field and a laser radiation. Under resonant condition of when photon sideband gap equals Landau level separation, a new intra-level plasmon mode emerges. The new mode increases rapidly with the decreasing magnetic field in the low field regime and behaves like a sound wave in the large wavevector regime.

Laser-induced fluorescence emission contains information about both spectra and time, so the different shapes, intensities and fluorescent lifetimes of fluorescence emission spectra can be used to measure the categories and contents of fluorescent substances with high sensitivity and good selectivity. To measure the oil micro-contamination in water, we utilized femtosecond ultraviolet laser pulse (fs Laser: MaiTai, Spectra Physics, US) as driving source and gated enhanced type ICCD (Time-resolved Fluorescence Spectroscopy, Lavision, German) as detector. We carried through laser-induced fluorescence measurement on DaGang crude oils and machine oils, accomplished data processing, and analyzed the differences of shapes of fluorescence spectra and lifetimes between crude oil and refined oil.

Q-switched mode-lock pulses train had been obtained stably in our microchip lasers as well as in our new modular semiconductor substrate microchip lasers. We are working on the applications of those Q-switched mode-lock pulses train to increase the measured resolution in the traditional time of flight as well as the phase enhanced high resolution time of flight laser range finder systems.

It is important to study the interaction effect between laser and photoelectric detector. In most of the laser detecting systems, laser must irradiate the photoelectric detector. The detector will be saturated or damaged easily if the fluence of the laser is higher than the saturation threshold of the detector. Now, many photoelectric detectors are used in space. To achieve their interaction, "Cat’s eye" effect is applied to find and locate the remote aerial detector by laser. The possibility and mechanism of disturbance to remote aerial detector induced by laser are analyzed, and the factors of influence are also analyzed. The fluence of laser on the photoactive area of remote aerial detector is estimated. With two samples of CCD and TV tracking system, the mechanism of soft damage to CCD and TV tracking system induced by laser are introduced. The saturation of CCD and crosstalk of CCD are the main reasons of disturbance. When the tracking system is used in wave-door tracking mode, it will lose its tracking target if the saturation or crosstalk of CCD can enter into wave-door. At last, the influence to disturbance induced by atmosphere effect is also analyzed.

The Laser-induced damage behavior of single-Crystalline Silicon was investigated with a Nd:YAG laser at 1064nm under single-pulse mode and free-running mode. It was found that the damage behavior of the SCS showed strong dependence on the output mode of the incident laser. From the experimental and theoretical analysis, the damage mechanism under the two laser modes were given based on thermal and thermal-stress coupling models.

A room-temperature Tm,Ho:YLF laser is constructed with a 2.5-mm-long Tm(6%) and Ho(0.4%) co-doped yttrium lithium fluoride crystal pumped by a laser diode operating at 792nm. The output power as a function incident pump power at different output coupler transmission values is given. At room temperature, the laser operates on a single transverse mode (TEM₀₀) at 2.066μm, the laser threshold pump power is 55mW, and its maximum output power and optical-to-optical conversion efficiency are 388mW and 14.1% respectively. At the same time, the output power and optical-to-optical conversion efficiency as a function of incident pump power at different temperatures are obtained. Furthermore, the experimental results are explained reasonably.

We apply the variational approach to solve the nonparaxial nonlinear Schrodinger equation to disclose the nonparaxial propagation properties of a Gaussian beam. A system of differential equations for the evolution of the parameters of Gaussian beam is obtained. The obtained analytical results clearly show the nonparaxial propagation process of periodic focusing-defocusing. This process is significantly influenced by the initial power and chirp of the beam. A positive chirp retards the first self-focus, while a negative chirp brings forward the first self-focus. Both positive and negative chirps increase the subsequent focusing-defocusing cycles.

We use the standard linear stability analysis to study the role of stimulated Raman scattering in spatiotemporal instability in dispersive Kerr medium based on an extended (3+1)-dimensional nonlinear Schrodinger equation. We show that the spatiotemporal instability gain spectrum consists of two parts: the conventional spatiotemporal instability gain spectrum and the Raman gain spectrum. Stimulated Raman scattering doesn't affect the conventional spatiotemporal instability gain spectrum; yet it provides additional sidebands which have almost the same gain spectrum in all combinations of the signs of group velocity dispersion and nonlinear refractive index. It is interesting that spatiotemporal instability gain can appear for any spatial frequencies in the presence of stimulated Raman scattering, in sharp contrast to conventional spatiotemporal instability whose gain is located in a limited spatial frequency range.

The resonance enhanced multiphoton ionization (REMPI) spectrum of SO₂ in the region of 420~540nm is obtained with a picosecond Nd:YAG laser pumped an Optical Parameter Generator and Optical Parameter Amplifier as radiation source. The ionization pathway is analyzed. SO₂ molecule is ionized though (4+1) or (4+2) process and via 4p, 5p and 6p Rydberg resonant states. The near quintic variation of the ionization signal versus laser intensity verified this conclusion further. So the spectral lines can be assigned to np Rydberg series. The adiabatic ionization potential and the quantum defect of SO₂ are obtained based on the experimental datum, which is 99586 cm^-1 and 1.85 respectively.

We propose a method of synchronizing chaos, which based on a certain parameter of two chaotic systems that is driven by the external chaotic signal. As a possible application we numerically investigated the synchronization of chaotic erbium-doped fiber dual-ring lasers systems. Numerical result shows that when the driving system is in chaotic state, if the driving stiffness is proper, the two chaotic systems will easily achieve completely synchronization based on new dynamics. When the driving system is in different states, the two systems can still retain synchronization, but the driving stiffness is larger than last case. On the other hand, it is found that the different synchronization states depend on the driving stiffness in erbium-doped fiber dual-ring lasers systems.

The laser-induced breakdown spectroscopy (LIBS) and laser-induced fluorescence (LIF) methods were applied for element and pigment concentration detection of marine water and phytoplankton samples. The spectra of plasmas generated by focusing the first harmonic λ = 1064 nm of a pulsed Nd:YAG laser on the liquid surfaces and phytoplankton samples in atmospheric pressure are described. Some of the chemical elements detecting by LIBS in the marine water (Na, Ca, Mg) and phytoplankton (Mg, Ca, Na, Fe, Si, Al) were defined. The radiation of second harmonic λ = 1064 nm of a pulsed Nd:YAG laser was used for phytoplankton pigments and dissolved organic matter detection by LIF. The results of joint application of LIBS and LIF measurements for phytoplankton communities state investigations inside Okhotsk Sea are presented.

Partially end-pumped slab laser is an innovative solid laser, namely InnoSlab. Combining the hybrid resonator with partially end-pumping, the output power can be scaled at high beam quality. In this paper, the output near-field and far-field intensity distributions are simulated by coordinate transformation FFT algorithm, comparing the thermal lens effect influence. As the simulated curves showed, the output mode is still good when the thermal lens effect is strong, indicating the good thermal stability of InnoSlab laser. The simulation is very helpful to design and optimize such slab laser.

A 1.5m long cell, different focusing lens, a KrF laser which bandwidth is 0.5cm-1, and SF6 gas as Brillouin medium are used in the experiment. The influences of SF6 pressure on threshold, energy reflectivity and pulse compression of stimulated Brillouin scattering excited by broadband KrF laser were investigated, respectively. For more precisely to explain the experimental results, a novel model considering optical breakdown and pump linewidth was presented. Optical breakdown is assumed to lead to the loss of pumping energy only. The experimental results are consistent with the numerical theory.

Laser treatment represents an attractive option to other methods of vessel diseases especially varicose veins. A long pulse (30~50ms) 532nm laser (Fig.1) is used in our experiments with the pulse duration matching the thermal relaxation time of the vessels and the green laser matching the absorption spectrum peak of the blood. Laser irradiates nude vein vessels directly or exterior skin to finish operation faster and to acquire the practical data for upper enteron varicose vein treatment in several animal experiments performed in vivo. The 5J-energy pulse allows us to finely occlude rabbit or dog’s vein vessels up to 2 mm in diameter when irradiating them off external skin (Fig.2). Blood vessels are occluded at once and later biopsy specimens show the immediate and long-term lasting occlusion effect. While irradiating vessels directly (Fig.3), the vessels are usually irradiated to perforate, detailed causes are still under investigation. Animal experiments show long pulse green laser therapy is a safe and effective solution to the vein’s occlusion, which promises such laser with high energy of each pulse and 30~50 ms duration is an ideal candidate for vessel diseases treatment.

Hollow lens duct is a good choice for the coupling system of the large-aperture high power diode arrays. With the help of numerical analyze of three-dimension ray tracing, we developed a computer simulation program for end-pumped LD arrays coupling system. Based on the result of simulation, we build a coupling system for an large-aperture (> 100 cm²) high-power (48kW) LD arrays, which include a hollow lens duct and a homogenizer, and coupled the pumping radiations into a laser crystal of only about 4 cm², coupling efficiency beyond 70% was reached with perfect pumping-uniformity in the gain material.

A survey of the Rydberg states of NO₂ accessed in optical-optical two-color double-resonant (OODR) manner by the technique of multi-photon ionization (MPI) spectroscopy is presented. The pump laser is the double-frequency output of a Nd:YAG laser. While the probe laser is an optical parameter generator and optical parameter amplifier (OPG/OPA) pumped by the triple-frequency output 355nm of the former. The OODR-MPI spectrum of NO₂ is obtained by scanning the probe laser in the range of 465-535nm under the condition that the pump laser is unfocused and the probe laser is focused on the center of the pump laser beam. The ionization peaks could be attributed to E²∑_u←A²B₂←X²A₁(1+2) resonant transitions. This means that NO₂ molecule is excited to the appropriate level of the first excited A²B₂ state by absorbing one pump laser (ω₁) photon. Then from the first excited state it should take three probe photons (ω₂) and via final resonant E²∑_u state for the ionization. The bending vibration frequency of NO₂ E²∑_u state obtained from above ionization spectrum is (608.6±2.2)cm^-1. It is consistent with the literature.

Sheet metal forming is a widely applied industrial process that can be found in the fields of aerospace and automobile panel’s production, the conventional forming of sheet metal is realized by the Die and Mold, this method usually give rise to high cost, long production periods and little flexibility. In this paper, a flexible forming technique of sheet metal based on laser shock peening is presented and some preliminary experiments were carried out with Nd:Glass laser of a pulse of 20 nanoseconds long and 1.064μm wavelength, an energy per pulse of 10 to 30 joules. The mathematical modeling of sheet metal bulging based on laser shock peening was established, and a finite-element analysis method based on the ABAQUS software is applied to simulate the sheet bulging process. The numerical simulation indicates that the results agree well with the experiments under one laser shock peening. The investigation revealed that the combination of numerical simulation and experiments is a useful method to obtain the optimized laser parameters, and to better understand the sheet deformation characteristics under laser shock loading.

For the advantage of long-life, high efficiency, low heat load and compact structure, diode pumped Laser (DPL) is used widely in different field such as military, communication and medicine etc. Diode-pumped Nd:YAG laser module is the integration of diodes (pumping source), coupling structure, cooling structure and laser medium through optimization. Being the core component of diode-pumped MOPA laser, the gain distribution of diode-pumped amplifier module influences the beam quality greatly. So it is very important to improve the uniformity of the module with high pumping power. This paper investigates, theoretically and experimentally, the elements which influence the gain distribute of laser medium. A high energy storage laser module have been manufactured. In this module a 8mm diameter Nd:YAG rod which is 120mm long is pumped by twelve diodes-arrays (the peak pump-power is 12kw). Each array is consisted of twelve diodes. Numerical calculation has been done to optimize the coupling structure. The experiment result approved that the gain coefficient of this module is 0.186/cm, from it we can infer that the storage power is about 700mJ per pulse.

A novel scheme of the face-pumped double-slab Nd:YAG slab medium cooled by liquid with different temperatures on both sides is proposed. In this structure the thermal distortion of wavefront caused by the non-uniform temperature distribution in the laser gain media can be self-compensated. According to the running mode, the model of the slab medium’s temperature distribution and stress are presented. The analytic solutions for the model are derived. Furthermore, the numerical simulations with pulse pumping energy of 10J and repetition frequencies of 500Hz and 1000Hz are calculated for Nd:YAG laser medium. The simulation results show that the temperature gradient remains the approximative linearity, and the heat stress is in the range of stress extremes. Then the absorption coefficient is also discussed. The result indicates that the doped concentration cannot be too larger for the high repetition frequency laser. It has been prove that high repetition frequency, high average output power of the order of kW of Nd:YAG slab laser with high laser beam quality can be achieved in this structure.

In this paper, numerical analysis was investigated for the double-clad fiber lasers and experimental study on the Yb³⁺-doped double-clad fiber lasers was performed. The results shown that the output power increased monotonically with absorbed power, and in lossy cavity the output power is less than in the lossless cavity. The output power decreases for the lossy fiber with the reflectivity of output coupler. There was an optimum fiber length to reach a maximum output and the optimum length was mainly dependent on the loss coefficient. In experiment we obtained an output power of 21.6W, slope efficiency of 54% by using Yb³⁺-doped double-clad fiber and 40W LD pump source.

The dynamic coupled modes (DCM) method has been applied to study the transverse mode competition in optical resonators. In this work a differential equation for the homogeneously saturating dynamic gain is included in the original dynamic coupled modes method, thus increasing its physical resemblance and allowing the retrieval of gain temporal evolution at every point within the lasing medium. This new model provides a realistic temporal evolution of the mode competition and gain saturation within the resonator, which can give further information of spatial coherence properties. The temporal information becomes particularly valuable when the laser transient is a matter of interest or when a continuous wave steady output is never reached, as occurs in pulsed lasers. Additionally, transverse spatial hole burning and inhomogeneous line broadening is straightforwardly included in the gain model. The application of the method to a typical CO₂ unstable confocal resonator is fully described, results and their connection to relevant physical properties of gas lasers, such as spiking and relaxation oscillations are discussed. Results of the numerical implementation of the DCM method with dynamic gain are in very good agreement with experimental measurements reported previously.

The propagation characteristics of Hermite-cosine-Gaussian beams passing through an ABCD optical system with hard-edge aperture is studied, by means of expansion of the window’s function of the hard-edge aperture into a finite sum of complex Gaussian functions, the approximate analytical propagation equations of laser beams are derived. This method is superd in its reduction of computing time, together with the convenience it furnished in analyzing physically the propagation properties of laser beams.

We propose and demonstrate a simple approach to lower the thermal quenching effect and improve the output power for Cr:LiSAF lasers, which is accomplished by employing two laser rods in a combined cavity. The resonator contains two laser rods and is designed by using two “X” folding cavities in cascade. CW laser output of ~ 230 mW has been achieved with pump of single-striped laser diodes. Compared with lasers with single gain rod, the laser with dual rods shows less severe thermal effect and increases the output by more than two times.

The entrance and exit surface damage has been observed in newly developed Neodymium doped phosphate laser glasses viz. Potassium Barium Aluminium Phosphate (KBAP), Lanthanum Potassium Barium Aluminium Phosphate (LKBAP), Yttrium Aluminium Phosphate (YAP) under Q switched Nd:YAG laser irradiation at 1.06 μm wavelength near normal incidence. The YAP glass is suitable for low repetition rate system such as range finders while KBAP and LKBAP find applications for high repetition rate systems which are used in material processing and electro-optic counter measures. The difference between the entrance and exit surface damage thresholds has been explained using electromagnetic effects. The comparison of the morphological features of the KBAP and LKBAP suggest the role of metallic inclusion in the samples whereas in the case of YAP sample, the damage is governed by the intrinsic physical properties of this glass.

In this paper a method for obtaining a high-power ultrashort pulse with ultrabroad bandwidth has been investigated. A theoretical investigation of the propagation and supercontinuum generation of the highly chirped pulse having been stretched and amplified are presented by numerical simulations in microstructured optical fiber. Comparing with the case of a chirp-free pulse, a chirped pulse with the same peak power and initial bandwidth can produce a broader supercontinuum spectrum with higher average power. After a felicitous compression, a high power ultrashort pulse that has an ultrabroad bandwidth much larger than that of the pump pulse can be produced.

High-power red laser are of great interest in the fields of medical application, laser display and also as a pumping source for tunable lasers such as Cr:LiSAF. This letter reports the generation of a 12W Q-CW red laser beam by intracavity frequency-doubling of a Nd:YAG laser operating at 1.3μm with a KTP crystal. A laser module that consisting of a Nd:YAG rod side-pumped by thirty 20W LDs of a triangle radial pump geometry, a acousto-optic Q switch and a KTP crystal were used in the experiment. Because the efficiency of SHG is sensitive to the type II phase-matching angles of KTP, we calculate the value of phase-matching angles according to several of Sellemier equations of KTP, and modify the phase-matching angles to θ=59.9° and φ=0° by experiment. The maximum average power of 12W of red laser is achieved at 10KHz when the pump power of LDs is about 470W.

The output characteristics of a large-core double clad fiber (DCF) laser are experimentally investigated in this paper. The fiber laser is fabricated with 5m Yb-doped DCF that consists of a 30μm diameter core and a 400/340μm D-shape inner clad. The measured spectra show that the wavelength of laser is not stable at low pump levels, and the wavelength tends to be stabilized at 1074nm until the pump power is increased to a level far over the threshold. The maximum output power of 7.2W is obtained at an input pump of 11W with a FWHM of about 6nm. The slope efficiency and the total conversion efficiency are 84% and 65.5%, respectively.

High power laser-diode-pumped 532nm laser sources (including continuous wave and high repetition rate operation) are directly used for precise processing of metals and plastics. Furthermore, high power green laser will be used in some fields such as ocean exploration, laser probe and underwater communication. Recently, we reported a 110W diode-side-pumped Nd:YAG intracavity frequency doubled high stability 532nm laser. In the experiment, we found that the average output power of second harmonic fluctuated acutely with the variety of pumping current. Moreover, the length of arms between the mirrors were very sensitive to this cavity. We consider that one of the reason is the focus length of thermal lens of Nd:YAG rod alter with the variational pumping current, which makes the cavity be unstable. We consider the KTP crystal as a thin lens for its short length. As thermal lensing effect of the Nd:YAG rod is quite severe, so we consider it as thermal lensing medium. By ray matrix methods, we have obtained the stable regions and beam waist radii distribution in the flat-concave cavity. In our experiment, we used a pump head consisting of 80 diode bars with pentagon pump model and employed flat-concave cavity structure in order to achieve high stability output and increase output power. The total cavity length is 505mm. By using an acousto-optic Q-switching with high diffraction loss and the KTP crystal which is type II phase matching, 110 W high stability 532nm laser is achieved. The experimental result is in good agreement with the calculation.

This paper reports a high output power, high conversion efficiency, all-solid-state, quasi-continuous-wave Ti:sapphire laser system pumped by frequency-doubled Nd:YAG laser with DPL and by employing it as a pump source, we got the tunable broadband wavelength varying from 750nm to 950nm. Comparing with correlative research fields, two uppermost improvements were achieved, including the topmost output power and its broadband tuning. To ensure the ideal broadband output of Ti:sapphire laser, two sets of Ti:sapphire resonator mirrors were used respectively One is from 750 to 850nm, the other is from 850 to 950nm. Because the centric wavelength of the resonator laser is nearly 795nm, the maximum of the Ti:sapphire laser output power we obtained was 6W with the first set of mirror and the transmission rate of the output mirror is 10%. The power tops this field so far and the higher conversion efficiency is 22.2%. The second set of mirror we used can generate the output power of 3W, which is high enough to achieve broadband tuning for the future. And then, by using a tunable and line width compressed implement-birefringent filter which was Brewster angle placed, we achieved continuous tuning from 750nm to 950nm with reasonably high power.

A new scheme of a liquid crystal Fabry-Perot etalon (LCFPE) had been proposed and designed on the basis of the electronically controlled birefringence of liquid crystal, some main aspects in the LCFPE design had also been considered, and such a birefringent LCFPE element with a free spectral range (FSR) of 125-GHz had been fabricated. An oscillation of 1064-nm single longitudinal mode had been observed when an empty LCFPE (i.e., without liquid crystal material) was inserted in a diode-pumped Nd:YAG laser cavity with an optical length of approximately 43-mm. In addition, the transmitted resonant mode splitting of a birefringent Fabry-Perot etalon had been investigated theoretically, and the dependence of splitting magnitude on the path difference between ordinary light and extra-ordinary light inside the Fabry-Perot resonant cavity had been given. The theoretically analyzed results indicate that the transmitted resonant mode of the birefringent Fabry-Perot etalon can split over a whole FSR, and the splitting magnitude changes linearly with the optical path difference.

Disk fiber laser is a novel fiber laser. The pumping scheme of such type of fiber laser is side pumping by LD arrays and the pumping scale is large in comparison with the core pumping manner in a typical clad pumping scheme. More pumping power could be coupled into the disk and higher output power could be achieved. To optimize the system of disk fiber laser, it is necessary to analyze the parameter of each part of it. In this paper, the configuration factors that influence the pumping efficiency of disk fiber laser were analyzed and propagation of the rays in disk fiber laser was simulated using the method of BPM. In the process of simulation, the fiber was treated as cylindrical lens. The optimal position of pump resource is obtained with a fixed size of the fiber cross section.

In this work, we numerically investigate the passive Q-switching performance of the tunable Cr:YSO Q-switched Cr:LiSAF laser over its entire tuning range. Specifically, the optical performance of the Cr:YSO Q-switched Cr:LiSAF laser as functions of the initial population in the ground state of the Cr:YSO saturable absorber, the pumping rate, the reflectivity of the output coupler, and the dissipative loss inside the laser cavity are studied. Simulation results show that the Cr:YSO is an effective saturable absorber Q switch for the Cr:LiSAF laser over its entire tuning range. Unlike the Cr:YSO Q-switched alexandrite laser and the Cr:YSO Q-switched Cr:LiCAF laser, the Cr:YSO Q-switched Cr:LiSAF laser has similar passive Q-switching performance when the laser polarization is along each of the three principal axes of the Cr:YSO. The results obtained numerically in this work are in good agreement with those obtained experimentally by other researchers. Our simulation results indicate that, a Q-switched laser pulse with an output energy of 10 mJ and a pulse width of 17 ns may be obtained at 850 nm, the peak of its tuning spectrum.

With a homemade laser beam profile measurement system, the characteristics of the spatial beam profile of 40 GW amplified femtosecond laser pulses have been studied. It is found that the laser beam profile has better quality at lower pump current, and the beam quality decreases as the pump current increases. In particular, the light intensity at the central area of the femtosecond laser beam may actually become weaker at high current than that at the low current. It is also found that within the multipass amplification process the beam quality of the pump laser has a great impact on the spatial beam profile of the femtosecond laser pulses.

We report on a theoretical analysis of propagation of monochromatic and broadband high-power laser beam through spatial filter. The law of formation of low-frequency modulation rings due to diffraction is obtained. It is found that the filling factor or the intensity modulation contrast of the laser beam is sensitive to times of diffraction limit of the filter’s pinhole. The uniformity of beam can be significantly improved by adjusting times of diffraction limit. For the same filter parameters, the broadband beam has a more uniform diffraction profile than the monochromatic beam, suggesting that the laser beam with a proper amount of bandwidth can suppress the harmful effect of diffraction to some extent.

Thermal heating is a major limiting factor in scaling the average power of a solid-state laser. In this paper some primary factors which affect the thermal effects of the typical side-pumped and side-cooled slab laser are discussed. The temperature and stress distribution in the cross-section in the laser crystal are calculated by using FEA. Some conclusions which optimize the performance of the side-pumped and side-cooled laser are drawn.

Possibilities to extract methane from methane hydrate are discussed. COIL is a unique solution from technological and economical stand points. COIL system suitable for excavation are proposed.

A multihundred-terawatt Ti:sapphire laser facility was built at China Academy of Engineering Physics which could deliver femtosecond pulses at three power levels of 5TW, 30TW and hundreds TW to targets. Near-diffraction-limited focal spots were measured and it was found for the first time that alignment errors of grating groove parallelisms in compressors could be the major mechanism for producing elongated far fields. Pulse durations of 35fs were obtained with a Fastlite-produced AOPDF for spectral compensation.

In this paper, the physical models of the code SG99, which is used to simulate the pulse behavior in high power laser system, are presented in details. The experimental results are also presented to show that SG99 is capable of simulating pulse propagation well and yields reasonable results. In the last, some results in design of TIL(Technical Integrated Experiment Line), the prototype of ShenGuangIII, are also introduced.

The characteristics of linear propagation and amplification of pulse in the high-power solid-state laser system were analyzed. The decomposition of linear propagation of the different parts in this system was also made. And the controlling means for beam quantity were put forward. At the same time, the measured near field and far field of the beam in TIL (Technical integrated experiment line, the prototype of SGIII (the Laser facility for ICF in China) were discussed, which proved these means were valid. These results of the theoretical analysis and experiment research become the general idea for investigating the problem of linear propagation in this system.

In the present work, directed toward using differential absorption lidar (DIAL) for measuring concentrations of pollutant gases, a galvanometer-driven mirror to scan a fixed diffractive grating for rapidly tuning a TEA CO₂ laser is reported. It is well known that the ground- or air-basing DIAL is an effective tool for remote measurement of pollutant gaseous concentration of the atmosphere over large areas. It has, practically in real time, the ability to remotely detect various gas concentrations in the atmosphere, because many pollutant gases have strong absorption lines within the spectral range of CO₂ laser wavelength tuning. In addition, the radiation of CO₂ laser is safe for the human eye and is well distributed in the atmosphere, coinciding with the “transparency window” of the atmosphere. Therefore the wavelength tunable TEA CO₂ laser is an ideal optical source for DIAL. The tuning is performed by generating and applying appropriate signals to the galvanometer, which rotated a silver mirror in order to scan the fixed grating. The device is driven by a programmable signal generator with resolution sufficient to rotate the mirror in discrete intervals as small as 70μrad, which is more than sufficient to find the optimum position for any lasing transition.

In this paper, experiments of a lateral semi-insulating GaAs photoconductive semiconductor switch triggered by nanosecond laser pulses were reported. The switches were insulated by solid multi-layer transparent dielectrics. Jitter-free electrical pulses with steady voltage amplitude from the 0.5 mm-gap GaAs switches were observed when biased with low voltage and triggered by serial laser pulses. Its change of amplitude was less than 1.2%, the triggered jitter-time was less than 10ps, and pulse width was up to sub-nanosecond. The effect of pulse energy change on the amplitude generated photoconductive semiconductor switch was analyzed. It was indicated that ultra-fast electrical pulse with steady voltage amplitude and pico-second triggered jitter-time can be obtained by controlling switch trigger condition and optimizing switch design.

Large, high-power laser amplifiers use the imaging properties of multiple spatial filters. Spatial filtering has been shown to control instabilities; spatial filters preserve the transverse intensity profile of a high power beam as it propagates long distances through nonlinear elements as well. In this paper, image relaying is presented as a technique for aligning beams onto mm-sized target. On base of summarizing the preceding work on the near-field image relaying of multiple spatial filters, the far-field image relaying is suggested firstly. The application of near-field and far-field image relaying properties of multiple spatial filters in laser beams automatic alignment system is analyzed. A geometrical optics approach and an ABCD ray matrix theory are used throughout. A reasonable and optimized scheme for automatic aligning multipass beam paths is presented. It is demonstrated on the multipass amplifier experimental system of the SG-III prototype.

A Q-Switched All-Fiber Cladding-Pumped Ytterbium-Doped Fiber Lasers using an acoustic-optic waveguide Q-switched (AOW-Q) with a pigtail fiber are studied. For AOW Q-switched, Ti-diffused YX-lithium niobate substrate was applied as optical waveguide, a SiO₂/In₂O₃ film of thickness ~150nm as acoustic waveguide and an acoustic aperture of width 110 μm, in conjunction with N=9 finger pairs.