The running characteristics of the single longitudinal mode, single polarization λ/4 phase-shift DFB Yb3+ -doped fiber CW lasers were researched. The fiber laser have the following excellent-characteristics: Output power of 25 mW, fluctuation of less than 2%, 100% single longitudinal mode, 30 dB polarization extinction ratio, 60 dB signal-to-noise. On the other hand, the effect on the fiber lasers is also researched from several factors such as temperature, mechanism perturbation and fresnel reflection of fiber end section.

At first, we made a approximative λ/4-shifted DFB Yb-doped fiber laser with double exposure method.The length of Yb-doped fiber is 10cm. Secondly, we processed the fiber laser by UV trimming. In addition, the running characteristics of the λ/4 phase-shift DFB Yb3+-doped fiber CW lasers were researched. The fiber laser have thefollowing excellent characteristics: Output power of 25 mW, fluctuation of less than 2%, 100% single longitudinal mode,27 dB polarization extinction ratio, 60 dB signal-to-noise. What is more, the effect on the fiber lasers is also researched from several factors such as temperature, mechanism perturbation and fresnel reflection of fiber end section.

This paper discusses a method of characterizing the gain of the laser pulse amplifier using its gain fluence curves and studies gain fluence Curves of a single amplifier．These help US to understand the characteristics of the amplifier and provide a powerful tool for the investigation of the power balance．

The "Shenguang-II" Facility laser uses an 8-beam double-pass architecture capable of delivering several KJ of infrared or ultraviolet energy in a temporal pulse format of an approximately 1ns quasi-square. Ideally the output wavefront of each beam from the main spatial filter should be a plane wave. But a real output wavefront of the laser light beam with a 200 mm section diameter in our facility is always a complex superimposed one. On its cross section, it has a distribution of curvature radius, which is called "local curvature radius" here. But the quality level of the output wavefront is mainly marked by its "global curvature radius", which is an assessing result based on the local ones. To meet the requirements of enhancing the conversion efficiency of the KDP crystal, each beam of wavefront out of the main spatial filter should resemble a plane wave as possibly as it can. Because only in this way can we achieve an optimal match between the injection direction of the laser beam and the functioning angle of the KDP crystal. In other words, the global curvature radius of each beam wavefront should be as large as possible. We have assessed the global curvature radiuses of eight beams, wavefronts by measuring their local curvature radii using Hartmann method. Finally, we have acquired better frequency conversion efficiencies by correcting each output wavefront to a better level according to the measurement results.

The Φ350 mm amplifier of No.9 laser of SHENFGUANG II demands the high gain coefficient, the good beam quality, the safety and stable running and the low cost. The gain coefficient has been raised by the improvement of pump lamps form and energy feed system, the design of Nd:glass, the suppression of the parasitic oscillation, the use of corner reflector, protective glass with sol-gel anti reflection film and high efficiency xenon lamps. The beam quality has been improved by the non-stress install of Nd:glass disks. The stable running has been enhanced by the improvement of cavity merit rating. The amplifier has been manufactured and installed. The characteristics of No.9 system have reached the design requirement.

For the first time to our knowledge, in a high-energy laser facility with an output energy of 454.37 J, by using a temporal–space-transforming pulse-shaping system with our own design of a knife-edge apparatus,we obtained a quasi-square laser pulse.

The temporal pulse shaping was realized by using temporal-space transforming pulse-shaping system with the own-designed “Knife edge” apparatus, for the first time to our best knowledge, in a large energy laser facility with the output energy of 454.37J. A quasi- square laser pulse with the pulse width of 1.16ns, the rising time of 337ps, the falling time of 360ps, and the temporal filling factor of 81.2% was obtained. It is quite satisfied with the requirement of physical experiment. In addition, the further improvements of our system have been suggested in order to enhance the stability and the flexibility as well as the restoring ability of the temporal-space transforming process.

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.

The laser beams automatic alignment system is used to adjust beam lines automatically in the high power laser fa2cility for inertial confinement fusion. Image processing is one of the key techniques in laser beam automatic alignment. Consider2ing the SG-Ⅲ, combining different kinds of methods in image processing such as threshold, gravity model, median filter, cir2cle fitting and so on, a reasonable scheme for automatic alignment was presented. It was demonstrated on the simulation experi2ment system. Results indicated that beam paths adjustment can be finished in 15 minutes by the automatic alignment system.The precision of the near field adjustment was less than 0.5 % of the spot. The accuracy of the far field adjustment was lessthan 0.3″. Requirements of the SG-Ⅲprototype facility are met.

This paper presented a new type of 5-DOF nanopositioning stage, and the design theory and method was introduced. The linear and rotarymotions of the stage was guided by flexure hinges and driven by piezoelectric actuators. Capacitive position sensors with nanometer accuracy were fixed on the stage to detect the displacement of motion and provide feedback signals to controller. The equation of compliant mechanisms and a design case are also presented.

This paper presents a new type of nanopositioning stage which has five degree of freedom; the stage is driven by piezoelectric actuators and guided by compliant hinges. The stage can be fabricated with an integrated metal through wire electro discharge machining and is compact. The equation of compliant mechanisms and a design case is also presented in this paper.

The displacement output ability of piezoelectric actuator is limited, for this reason, it was commonly to carry out amplification on its amount of displacement with the aid of flexible mechanism. At here an analysis was carried out on the performance of the commonly used flexible amplification mechanism. A kind of flexible eight-link amplification mechanism has been put forward, and the finite element analysis and theoretical calculation were conducted upon it. A two staged series mechanism has been put forward so as to raise the rate of amplification. Entirety of the mechanism possesses the advantages of compact in structure and rather high amplification efficiency.

Theory and experiment haw demonstrated that the coherent addition of multiple small gratings to form a larger grating is viable. an approach referred to as grating tiling. and the key technology of which is to control the relative position and orientation of each grating with high precision. According to the main factors that affect the performance of the tiled grating. We develop a five-DOF ultraprecision stage for the tiled grating experiment. The design and control of the mechanism is discussed and part of experiment results is presented.

The X-ray laser is a useful tool in denseplasma diagnostics because of its shortwavelength, high intensity and coherence. A brief descrip tion of its applications is given here based on various demonstration experiments, including an introduction to the principle of plasma diagnostics, the fabrication of X-ray lasers, and the results of diagnostic experiments using the Moirédeflector and Mach-Zehnder interferometer.

This paper discussed the influence of the pertinence of two couples of physical parameters on the uncertainty of particle velocity and the shock pressure of test sample. The influence was estimated f rom calculation of experimental data. By a great deal of experimental statistic data, the influence of the pertinence of Hugoniot parameters on the uncertainty of particle velocity was less than 0.7‰, and the influence of the pertinence of physical parameters shock velocity and particle velocity on the uncertainty of shock pressure was about 0.5%

The interferometry with an X-ray laser as probe is an important tool of diagnosing the electron density of a high temperature and dense plasma. A successful experiment of diagnosing the density of a CH plasma was demonstrated by using a Ni-like Ag X-ray laser as a probe and a Mach-Zehnder interferometer as instrument under the Shenguang II laser facility. The legible interferogram indicating the information of electron density was obtained.

Employing the inner-shell transition mechanism is a potentialway to obtain ultra-short wavelength lasers. It is not a hopeless dream to produce an ultra-short wavelength hard X-ray laser using thismechanism, in light of the recent great developments in ultra-fast and ultra-intense laser technology as well as experimental X-ray laser research. In this paper the principle of inner-shell X-ray lasers is introduced and some possible approaches to the realization of such lasers are discussed in detail.

By means of the Huygens-Fresnel diffraction integral, the propagation expression of a laser beam passing through a hard-edged aperture is derived. The effects of the bandwidth on the transverse intensity distributions of the beam in the near and far fields are analyzed. It is found that, in the near field, the beam uniformity is improved with increasing the bandwidth and the broader the spectrum, the smoother the transverse intensity distribution is. Intensity spikes produced by low-frequency diffraction are eliminated in the diffraction patterns and the transverse intensity distribution near axis tends to smooth when the bandwidth increases. The intensity spikes produced by high-frequency diffraction still exist with increasing the bandwidth, but the amplitudes and numbers of them decrease. In the far field, there are only a few differences among the transverse intensity distributions of the beams with different bandwidthes. However, The secondary maximum intensity still presents for the beam with small bandwidth, and it decreases with increasing the bandwidth and is eliminated with large bandwidth.

A closed-form propagation equation of Hermite-cosh-Gaussian beams passing through an unapertured thin lens is derived. Focal shifts are analyzed by means of two different methods according to the facts that the axial intensity of some focused Hermite-cosh-Gaussian beams are null and that of some others are not null but the principal maximum intensity may be located on the axis or off the axis. Optimal focusing for the beams is studied, and the condition of optimal focusing ensuring the smallest beam width is also given.

By using complex amplitude envelope representation and complex analytic signal representation, propagation expressions of Lorentz pulsed beams are derived. Propagation properties of them with different bandwidths are illustrated by numerical calculations. It is found that they are the same in the neighbourhood of z-axis for narrowband pulses, but in the case of broadband pulses, singularities emerge near z-axis for pulsed beams obtained by using complex amplitude envelope representation and only complex analytic signal representation is applicable. The conditions to decide what representation should be chosen to study pulsed beams are given. And the origin that results in the emergence of singularity is given.

In this paper we theoretically study the left-handed behaviors in a two-dimensional triangular photonic crystal made of elliptical rods in air. An absolute left-handed region is found in the second photonic band by using the plane wave expansion method to analyze the photonic band structure and equifrequency contours. Typical left-handed behaviors such as negative refraction, flat superlensing and plano-concave lensing are demonstrated by the finite-difference time-domain simulations. These behaviors are also compared with the quasi-negative refraction and the resulted focusing effects in a square-lattice two-dimensional photonic crystal.

Analytic propagation expressions of pulsed Gaussian beam are deduced by using complex amplitude envelope representation and complex analytic signal representation. Numerical calculations are given to illustrate the differences between them. The results show that the major difference between them is that there exists singularity in the beam obtained by using complex amplitude envelope representation. It is also found that singularity presents near propagation axis in the case of broadband and locates far from propagation axis in the case of narrowband. The critical condition to determine what representation should be adopted in studying pulsed Gaussian beam is also given.

Organosilicone composite antireflective (AR) coating was successfully prepared for Ti-sapphire crystals by sol-gel process from precursors of tetraethoxysilane [Si(OC2H5)4, TEOS] and methyltriethoxysilane [CH3Si(OC2H5)3, MTEOS]. This AR coating possessed prominent AR effect within the output waveband (750～850 nm) of Ti-sapphire laser with average transmission above 98.6%, and its surface homogeneity met the requirements of the laser wavefront. The laser induced damage threshold (LIDT) of 2.2 J/cm2 was obtained at 800 nm with the pulse duration of 300 ps for this AR coating on Ti-sapphire crystals, which made it suitable for the optics of ultrashort pulse pico- and femtosecond high power lasers. Further, investigations on the performance of coating solution showed that the viscosity and coating refractive index both increased along with MTEOS prepolymer content, and effect of bake temperature on the latter was very small.

Irradiation uniformity of laser on target is very important for inertial confinement fusion (ICF). The theory of smoothing by spectral dispersion (SSD) in ICF is studied by translation theory of optic, and with whether using of SSD and different parameters of SSD, the variations of irradiation nonuniformity of the surface of target are numerically simulated combined with random phase plate (RPP). The results show that application of SSD can reduce the irradiation nonuniformity of the surface of target, the variations of irradiation nonuniformity with the time are oscillating at the beginning and drive to a constant in the end. When the number of color cycle is small, the broader of laser bandwidth and the better effect of SSD are obtained.

Starting from paraxial wave equation, analytical propagation expressions of hyperbolic secant pulsed beams with narrowband and broadband are derived. By the use of numerical calculations, pulsed beams obtained by means of complex amplitude envelope representation and complex analytical signal representation are compared. The condition to determine what representation should be chosen is also given. It is found that pulsed beam obtained by using complex amplitude envelope representation has singularity, which is anti-beam behavior and loses physical meaning. In the case of pulsed beams with broadband, singularity of complex amplitude envelope solution locates near axis, which causes that the solution failed to describe pulsed beam. But for the case of pulsed beam with narrowband, singularity locates far from axis, which can be neglected in the study of pulsed beam. It is concluded that both of the representations are applicable to study narrowband pulse, but for broadband pulse only rigorous complex analytical signal representation should be adopted.

Although the porous silica antireflective (AR) coating has high laser damage threshold after heat treatment, its transmission is correlated with environment relative humidity due to many Si-OH hydrophilic groups on the coating surface. The aim of the experiment is to modify internal component, enhance the hydrophobic performance and improve the transmission stability of the films. In this paper, Si-O-Si(CH3)3 non-polar hydrophobic groups appear on the coating surface through atmosphere treatment of ammonia and HMDS (hexamethyl-disilazane), causing hydrophobic performance, thus the stability and life of AR coating are improved greatly. This is very important for coating to use in laser device. The results also show that the coating surface is smooth after above treatment, and its roughness is estimated to be 3.575 for root-mean-square value and 2.850 for average value which meets the precision requirement of large scale laser.

A clear and stable self mode-locked pulse train was observed with Q-switched pulse envelope in diode pumped Yb-doped Q-switched fiber lasers. Self phase modulation (SPM) is regarded as the main reason to generate mode-locked pulses in this Q-switched fiber laser. The main effect of SPM is to broaden the spectrum of the optical pulses. If the width of the broadened spectrum is comparable with the cavity-mode spacing then the modes can interact with each other, and a fixed-phase relationship between different oscillating axial modes is maintained, resulting in the mode-locked operation. On this basis, the acousto-optic modulator (AOM) was removed and two gratings were used as the cavity mirrors, and an all-fiber Fabry-Perot (F-P) cavity fiber laser was realized. Similar mode-locked pulses were observed when using two ring reflectors as the cavity mirrors. It is observed that mode-locking has close relations with fiber length, Yb-doped concentration and pump power. Such kind of lasers provide a new method to generate mode-locked pulses.

The distribution of optical field passing through lens array is analyzed. Lens array consists of many array units, which can improve energy distribution uniformity around the focus of main lens. Lens array improves illumination, but it brings bad affection to energy measurement. The reason is that intervention will happen between sub-beams after the array units, thus energy density and power density of laser on the interference stripes will increase sharply. Its value will augments to four times contrasting to former one. The higher energy and power need more severe criteria to calorimeter. If proper means is not taken in use, calorimeter will be destroyed.

(CH3)2Si(OC2H5)2 as precursor, a sol of good stability is prepared by sol-gel method and organic synthesization. After the sol is coated it on phosphate laser glass by rotating way, moistureproof film is worked out, having a transmittance of 96.5% after heated. The film has a good morphology, roughness of mean square (RMS) of 1.659 nm and roughness of average (RA) of 1.321 nm. The damaged threshold of the moistureproof film is high to 10～14 J/cm2, tested by a laser of wavelength of 1053 nm and pulse width of 1 ns. In the period of 5 years on “Shenguang Ⅱ” high power laser equipment, it behaves good moistureproof performance , and tryouts on “Shenguang Ⅲ” model.

A new laser pulse-shaping system using an electro-optic modulator driven by an aperture-coupled-striplines (ACSL) electrical-waveform generator has been discussed in this paper. The ACSL electrical-waveform generator consists of two striplines coupled through an aperture in their common ground plane. Replacing the aperture layer, the electrical-waveform can produce arbitrary electrical pulse with 150 ps structure. Giving the arbitrary electrical pulse to the electro-optic modulator, arbitrary optic pulse can be gotten. By the new technique, the laser pulse-shaping system is capable of producing arbitrarily shaped laser pulses with about 150 ps structure, 1～3 ns pulse envelope, high contrast waveform and slippery transition waveform.

Porous SiO2 antireflective (AR) coatings are prepared from the colloidal silica solution modified with methyltriethoxysilane (MTES) based on the sol-gel route. The viscosity of modified silica suspensions changes but their stability keeps when MTES is introduced. The refractive indices of modified coatings vary little after bake treatment from 100 to 150 Celsius. The modified silica coatings on Ti:sapphire crystal, owning good homogeneity, display prominent antireflective effect within the laser output waveband (750-850 nm) of Ti:sapphire lasers, with average transmission above 98.6%, and own laser induced damage thresholds (LIDTs) of more than 2.2 J/cm2 at 800 nm with the pulse duration of 300 ps.

Microstructure optical fiber with uniform intensity distribution of the fundamental mode is proposed. The design guide line and characteristics of this kind fiber are demonstrated. The relationship between refractive index profile and structure parameters is investigated. The mechanism of forming uniform fundamental mode in these fibers is analyzed.