Experiments indicate that the size and shape of the final focal spot are mostly dictated by phase noise added to the beam. To diminish the static phase aberrations of large aperture lasers and promote the concentration degree of focal spot, phase corrector plate is proposed. For the technical integration line (TIL) being built in China Academy of Engineering Physics (CAEP), phase aberration of the main amplifier is the largest contributor. Considering peak fluence of the inserting places and the machining process of the phase plate, four potential locations are evaluated, and the cavity mirror is chosen to be the preferred place and is replaced by the phase plate. Numerical calculation model is established to design the corrector plate. Cut-off frequency of the glass-slab filter is discussed and 0.01 mm-1 is optimally chosen for the lowpass filter. The surface shape and the machining technique of the phase plate are given. Using SG99 light propagation code, simulations demonstrate that the corrector plate can effectively compensate optic finishing errors, and static phase aberration is decreased from 3.35λ to 1.27λ. Further more, times diffraction limit (TDL) containing 95% energy of focal spot is improved from 6.21 to 3.95.

Locking laser to a proper reference frequency can obviously improve the laser′s frequency stability.The optical path and frequencies are different for axial and paraxial beams traveling through a confocal Fabry-Perot (CFP) cavity, thus the frequency difference between them which is a dispersion-like signal can be used to stabilize the laser frequency. Thus the phase-sensitive detection via lock-in and frequency dither on the laser or cavity are no longer required. With this modulation-free stabilization method, a homemade 852 nm grating-external-cavity diode laser is stabilized to a CFP cavity frequency, whose frequency jitter is less than ±340 kHz in 30 seconds estimated from locked error signal. The long-term frequency stability was greatly improved compared with the frequency fluctuation of about 10 MHz under free-running condition in the same time scale. Moreover, the frequency shift and the zero-crossing slope of the dispersion-like frequency-discriminating signal can be conveniently changed by adjusting the angle between the two incident beams. The laser frequency stability locking with different frequency interval is investigated.

High power xenon flashlamp is mainly used in inertial confinement fusion (ICF) research as optical pump source for solid-state lasers. Its working performance and life time greatly influence the operation of lasers. A high power xenon flashlamp with relative small-bore and large arc-length is manufactured based on the development of tube material and wall structure. Two specifications are researched: one is diameter of 16 mm and arc-length of 1140 mm; the other is diameter of 17 mm and arc-length 1270 mm. The flashlamp has higher radiation efficiency compared with previous flashlamps. High explosive energy and satisfactory life time ensure its large output energy and good working stability.

To analyze the effects of applicator types and emitting characters on laser-induced interstitial thermotherapy (LITT), based on an optical-thermal mathematical model considering the dynamic changes of physical properties during laser heating, the sizes and shapes of thermal damage regions for bare fiber tips and diffuse applicators were numerically calculated and compared. The effect of the un-uniform emitting radiation of practical diffuse applicator on the thermal damage region was also analyzed numerically. The numerical results showed that the thermal damage region with diffuse applicator was much larger than that with bare fiber for long time heating. The thermal damage region was not spherical symmetry about the fiber tip for bare fibers while approximately ellipsoidal for diffuse applicators. The numerical results also showed that the thermal damage region was not sensitive to the un-uniform emitting radiation of practical diffuse applicators. Applicator types and emitting characters significantly affected the thermal damage regions during laser-induced interstitial thermotherapy.

The study of fractional Talbot effect of the 2D amplitude skewed array is very important to the designation and manufacture of the new type array illumination. The fractional self-imaging effect of the 2D array with arbitrary shape and symmetry is studied theoretically, using scalar diffraction theory and the known periodic self-Fourier-Fresnel transform function comb(x,y). As a result, a general equation to calculate the phase of the fractional Talbot image of the 2D array is also got. As an example, the intensity distribution of the 60° skewed diamond periodic array in different fractional Talbot planes is numerically evaluated using Matlab. The result is a good agreement with the theory. Based on the theory, the reliability of the designation and manufacture of this skewed diamond array illumination is briefly discussed. Additionally, comparisons of the characteristics are made for the 2D amplitude skewed array and the 2D amplitude orthogonal array in the compression ratio and shape of the light spot.

Both dynamic mechanisms and diffraction characteristics of the local volume photorefractive holographic gratings recorded by two finite bounded plane waves in doubly doped LiNbO3:Fe:Mn crystals are investigated, by taking into account both the band transport model and two-dimensional coupled-wave theory. The three step method is used to solve both the band transport equation and the two-dimensional coupling equation. The numerical calculations show that the spatial distribution of the space-charge field is non-homogeneous in the local volume photorefractive holographic gratings. The space-charge field is much stronger when the grating region is smaller. As the grating region widening, the space-charge field decreases by an order of magnitude. Besides, the time-space variation of the space-charge field is the same as that of one dimension infinite photorefractive holographic gratings in the place closer to the incident boundary. But the influence of the special local effect on the space-charge field is very important as the grating region extends. It is also shown that the diffraction efficiency increases with the increase of the grating length of the local volume photorefractive holographic gratings. The theoretical results provide valuable insight to the design and application of these gratings and the finite boundary photorefractive holographic optical elements.

800 MPa grade new ultra-low carbon bainitic (NULCB) steel was welded by laser welding and melt-active gas (MAG) welding, and the microstructure and mechanical properties of the heat-affected zone (HAZ) were investigated. The experimental results indicate that the microstructure of the HAZ is only granular bainite which consists of the bainite lath and the martensite-austenite (M-A) constituent. As the heat input that was adopted in the experiment increases, the average width, gross and shape parameter of M-A increase, but the line density decreases. The toughness of HAZ is higher than base metal under appropriate laser welding conditions. With the heat input of laser welding increase, the hardness of welded joint decreases, but it is higher than that of the base metal, indicating no softened zone appeared after laser welding.

Under the severe condition of high temperature and heavy load, electroplating chromium coating is extremely easy of premature spallation so that the service lifetime of components is dramatically reduced. Laser phase transformation hardening was used to pretreat the superficial layer of substrate before electroplating in order to improve bonding strength between the electroplating coating and the substrate and enhance the load endurance. The microstructure and interface of electroplating chromium coating were analyzed by scanning electron microscopy (SEM). The hardness variation of electroplating coating, phase transformation hardening zone, and substrate were analyzed. The ability resisting high temperature ablation was measured. The results showed that laser phase transformation hardening on the substrate could not only effectively promote the epitaxial growth of electroplating chromium coating, but also realize the gradient variation of the hardness from electroplating chromium coating to substrate. Consequently, the bonding was improved, the stress was alleviated, and the load endurance was enhanced. So the spallation resistance and the service lifetime of electroplating chromium coating were evidently enhanced. It was a main reason for the epitaxial growth of electroplating chromium coating that the refined quenching martensite was obtained, the dislocation density was evidently increased, and the surface activity was increased by laser phase transformation hardening.

Keyhole effect and its periodical fluctuation are important characteristics of deep penetration laser welding processing. The plume fluctuation over laser keyhole arises from the pressure fluctuation of keyhole gas. It is validated by plume behavior obtained from a series of plume images by a high-speed videography system, and the expanding speed of hot gas emitted from laser keyhole in the workpiece is determined. Then, a mathematical model for the simulation of characteristic weld gas shield phenomena during deep penetration laser welding based on a numerical solution of the equations of species, mass, momentum and energy is presented. Important differences are observed between Ar gas shield and He gas shield. All these experiments are also simulated using the 3D hydrodynamic software Fluent. It is seen that the characteristic size of argon gas shield is larger than that of helium gas shield, and the smaller the nozzle inclination angle, the larger characteristic shield size of the assist gas. The effective protection zone will be increased when the flux rate of the nozzle assistant gas is increased. The expansion speed of the plume over laser keyhole is much smaller than 150 m/s. The maximum mass fraction in the species flow zone is smaller than 0.9.

Laser welding technology was adopted to weld Zr-base bulk amorphous alloy (BAA) Zr45Cu48Al7 (at.-%) plate. The structure of joint under different technical parameters during laser welding was researched, and the crystallization behavior of the bead and heat-affected zone (HAZ) during the thermal cycle of welding was primarily discussed. The results showed that an excellent joint has been obtained and there was no visible defect, pore or crack in both the bead and HAZ when the output power of laser-beam was 1200 W and the scanning velocity was 8 m/min. No crystal was observed in both the bead and HAZ with keeping the amorphous structure. However, crystallization occurred in both the bead and HAZ under the condition of the same output power but the scanning velocity of 2, 4 m/min. From the optical microscope and the micro-focused X-ray diffraction (XRD) experiment, it made sure that there was crystal in both the bead and HAZ under the scanning velocity of 2 m/min and the crystalline phases were mainly ZrCu phase and Zr38Cu36Al26 phase (τ5). There was some crystal in HAZ while no crystal in the bead under the scanning velocity of 4 m/min, and the crystalline phases were almost the same as under 2 m/min scanning.

A laser diode array (LDA) with the micro-lens two-side-pumped Yb:YAG slab laser was reported, the Yb:YAG slab was in size of 6 mm×10 mm×1 mm, and the doping concentration was 3 at.-%. A novel structure was designed to focus the pump beam to as small as 10 mm×1 mm in size. The transmission efficiency of the structure is about 75% and the pump intensity could be reached as high as 1.9 kW/cm2 on the surface and 38 kW/cm3 in the bulk that is more higher than the threshold of 1.7 kW/cm3. The maximum output pulse energy of 25.5 mJ with slope efficiency of 13% was obtained from a plano-concave cavity with an output coupling of 6%. Once an acousto-optic modulator (AOM) was inserted into the cavity, Q-switched pulse with energy of 4.7 mJ and pulse width of 24.8 ns were achieved.

An actively mode-locked fiber ring laser based on cross-gain modulation (XGM) effect of semiconductor optical amplifier (SOA), with a small intracavity loss, is proposed and demonstrated. By using an optical circulator, the intracavity loss was reduced and the output power of the laser was increased. The physical mechanism of pulse multiplication in ring cavity during rational harmonic mode locking process has also been theoretically analyzed in detail. Taking advantage of rational harmonic mode locking technology, an optical pulse train with a repetition frequency of 30 GHz was obtained using a modulation frequency of 10 GHz, and the peak power was about 0.5 mW. With broad gain spectral width of SOA and large tuning range of filter, the output power of the output pulse train could keep big enough over a large tuning range. Harmonic mode locking at 20 GHz was successfully achieved and the peak power of the output pulse train was more than 0.65 mW over a 40 nm tuning range. The semiconductor optical amplifier and the short length of the ring cavity ensure the long-term stability of the laser.

Stimulated Raman scattering (SRS) can affect the power scaling of high power fiber laser. According to the power transfer equations, SRS effect in high power Yb3+ doped double clad fiber laser is studied. The effect of core diameter, fiber length, doped concentration and pumping method on the characteristic of fiber laser is studied. The way for suppressing SRS, such as increasing core diameter, decreasing fiber length, reducing doped concentration and using reasonable pumping method, is discussed. The theoretical model is proved by the experimental result.

The result of influence on outcoupled mode by introducing intracavity mirror tilt-perturbation in positive-branch confocal resonator is analyzed. The intracavity mode distribution and its Zernike-aberration coefficient due to the concave or convex mirror tilt disadjustment are calculated by adopting equivalent lens method. At the same time, the experimental study about the relations of intracavity mirror tilt disadjustment and mode aberration has been performed by using Hartmann-Shack (H-S) wavefront sensor method. Aberrations of outcoupled beam mode are obtained by using mode-reconstitution method. The results show that the intracavity perturbation of concave mirror has a greater effect on outcoupled beam-quality compared with that of convex mirror. For the large Fresnel-number resonator, the tilt angle of intracavity mirror has a close linear relationship with extracavity Zernike tilt aberration coefficient. The ratio of Zernike tilt coefficient approaches to the magnification of unstable resonator if equivalent perturbation is applied to concave mirror and convex mirror respectively. Furthermore, astigmatism and defocus aberration are also increased with the augment of tilt aberration of beam mode. So intracavity phase-corrected elements used in unstable resonator should be close to the concave mirror. The wavefront relationship between the He-Ne laser and the actual laser beam has also been compared.

Ultrafast temporal unequally-spaced space-time conversion and recognition technique for Dammann-type filters is analyzed. The multiple pulse Dammann-type filter for specific unequally-spaced and equal-intensity filter were designed. With the simulation of a Gaussian spectral distribution, the correlation between the perfect uniformity of the generated multiple ultrafast temporal pulses and the repeated number of modulation periods of the mask in the spectral plane is discussed. Moreover, experimental result of recognizing the two ultrafast femtosecond pulses by the frequency-resolved optical gating (FROG) technique is also given.

Taking into account the saturable nonlineary of the optical fibers, the coulped nonlinear Schrdinger equations of the slowly varying envelopes for two optical waves of different frequencies with the same polarizations, and the linearized nonlinear Schrdinger equations for the perturbations are given. In the normal dispersion region of optical fibers, the variation law of the gain spectra of modulation instability induced by cross-phase modulation with the input powers of the two waves is analyzed and discussed. The results indicate that, similar to that of the gain spectra of self-phase modulation induced modulation instability in optical fibers with saturable nonlinearity, the critical perturbation frequency as well as the peak gain of cross-phase modulation induced modulation instability also increases with the input powers before decrease. The varying velocity of the two parameters is related to the perturbation frequencies. This may lead to a unique value of peak gain and critical perturbation frequency for two different input powers.

An improved iterative phase retrieval algorithm is put forward, which makes use of intensity information in several planes, and divides the retrieval process into two steps: profile retrieval and detail retrieval. First the input plane and other three far diffraction planes are needed to retrieve the profile of phase distribution, then the phase detail is available in a similar way. The phase distribution of any one dimensional optical field, including very complicated ones, can be successfully retrieved with this algorithm, and the accuracy of retrieval is greatly enhanced. This algorithm is also very robust. It has convergence independent on the initial phase, and high stability towards additive noise, which are both confirmed by simulations.

Photon localization is the fundamental property of microstructure fibers. A method of coherent back scattering for measurement on micro-structure optical fibers (MOFs) is proposed. In order to understand and explain the theory of photon localization, the quartz-crystal, integrated multimillion micro-structure optical fiber and dual-core micro-structure optical fiber were measured in the visible region. Based on the wave classical transmission theory, the experimental equipment for the measurement was setup. The experimental results reveal that there is not interference phenomenon for quartz-crystal, but some strong interference apexes for micro-structure optical fibers at 575 nm. Because of the existence of the periodic structure from the vein region to the node region in 2D micro-structure optical fibers, the dimension is around 500～600 nm which is corresponding to some discontinuous scattered particles, when the wavelength is 575 nm, the dimension is close to the particles which meets the condition of photon localization. Therefore, the phenomena of strong coherent back scattering come into being.

At present, functional organic molecule is a study focus in exploitation of new type photoelectron material and photosensitizer of photodynamic therapy (PDT), therefore it is necessary to study a new-type photosensitizer hypocrellin A (HA) which belongs to excited state intramolecule proton transfer (ESIPT) molecule, that is, HA′s basic properties of spectroscopy and electronic excited state properties. As a result, the stimulative phenomenon of HA is found, the rage of laser emission is 620～800 nm, providing a new proof for ESIPT under intense excitation. The fast process of HA′s excited state is investigated by transient grating technology, it is believed to be a result from the decay of transitional state (TS*) produced by skeleton rearrangement. Its lifespan is 10.5 ps.

Quasi-velocity-matching can be used to realize electron-optics phase modulator with high modulation index, which has essential applications in spectroscopy, laser frequency conversion and improving laser beam uniformity. When laser beam with high power propagates through the modulator, the larger aperture of the device is necessary, so the poling technology on ferroelectric crystal with large-area and high-thickness is essential for high power quasi-velocity-matching. In this paper, the electrical-poling process in room temperature on LiTaO3 crystal with the thickness of 1mm is studied in detail. In order to restrain back current during poling process, control of electrical poling time is adopted in the experiments. large-area domain inversion of LiTaO3 is successfully realized proved by thermoelectric effect and chemistry etching method. The proposed technology can be also employed in other ferroelectric crystal poling.

New laser materials have been explored continuously due to the long growth time and high cost of the crystals. Transparent ceramic is one of the latest developed laser materials. In this paper, polycrystalline Nd3+:Gd3Ga5O12 (Nd3+:GGG) nanopowders for transparent laser ceramic were synthesized by sol-gel method. The sample crystalline phase and shapes were analyzed with X-ray diffraction (XRD) and scanning electron microscope (SEM). The results indicated that Gd3Ga5O12 (GGG) nanometer powders with sphere shape and homogeneous dispersion were obtained when the samples were fired at 1000 ℃ for 12 h. The size of precursor particles increased with increasing of the sintering temperature. The strongest fluorescence emission peak appeared at 1062.7 nm which corresponds to Nd3+(4F3/2→4I11/2) transition.

Inertial confinement fusion (ICF) establishment needs lots of high quality, large caliber and non-linear optical material potassium dihydrogen phosphate (KDP), which is water-soluble crystal. It is necessary to prepare a moisture-barrier protective film with good performance on the surface of KDP crystals. Antireflective SiO2 coating has been prepared by tetraethyl orthosilicate (TEOS) and sol-gel route with dip coating method. The surface of SiO2 film was disposed with teflon AF2400. The properties of the AF2400-SiO2 composite film had been characterized and measured by atomic force microscope (AFM), Fourier transform infrared (FTIR), UV-VIS-NIR spectroscopes etc. The experimental results show that the light transmission of AF2400-SiO2 composite film is 97.7% at 355 nm, the refractive index is 1.21. The AF2400-SiO2 composite films have fine water-repellent performance, high laser damage threshold (19.5 J/cm2) and excellent optical property. The composite film can be used for protection of KDP crystal.

Considering the influence of the probe beam size on the modulated photothermal reflectance (MPR) signal, a three-dimensional theoretical model of laser-induced MPR for the thin film-on-substrate system is presented in this paper. The feasibility of measuring the thermal parameters on thin films by MPR techniques is investigated. The effects of the material parameters on MPR signals are discussed in detail. The numerical multiparameter estimation of thermal properties is also performed in this paper using the frequency response of MPR signals (i.e. MPR frequency scanning method). Three thermal parameters, i.e. the film′s thermal diffusivity, the substrate′s thermal diffusivity and the thermal resistance on the film-substrate boundary, are simultaneously determined. It is shown that, comparing with the conventional MPR radial scanning method, there is no strong correlation among the three thermal parameters in MPR frequency scanning model. Therefore the convergence and the accuracy of multiparameter estimation for samples can be improved by MPR frequency scanning method.

By simultaneous switching of transmitting and receiving beams in an electro-optical device, a novel laser ranging method is proposed. Continuous wave (CW) laser emitted by laser transmitter goes forward to the measured object, being reflected by the object, then goes back to the transmitter. Close to the transmitter, an electro-optical crystal is added into the round-trip light rays. High voltage curve with the steep enough edges is added on the crystal. Because of the high speed switch effect, the crystal operates on the transmitting and receiving beams at the same time. So light pulses, whose width T contains the required range information, are cut off and detected. In experiments the changing time of high voltage is about several nanoseconds realized by avalanche triode circuit. And based on double refraction and total internal double reflection effect in crystal, a single block LiNbO3 crystal with special shape is designed as the main device of this method. The feasibility of the new idea is proved by the results from oscillograph. So a brand-new way for the laser ranging is provided.

Eccentric photorefraction (EPR) is a technique for measuring the refractive state of the human eye. Up to now, the crescent formation and light-intensity distribution of the pupil image in eccentric photorefractometer are all analyzed by geometrical optical theory, and the diffraction effects are neglected. For improving the accurateness of theoretic analysis, a space variable method based on wave optics is presented. The creation of crescent is proved to be a space variable process, and the pupil image and the corresponding intensity distribution on the meridian for different myopic diopters are simulated by computer. The simulated results are compared with those obtained by geometrical optical theory and show that the method is more accurate.

During precise measurement of high reflectivity, cavity misalignment has great influence on reflectivity measurement results of ring-down spectroscopy. According to propagation equation of Gaussian beam and overlap-add of signal, a theory model is set up to research the influence of detector on its ring-down waveform by using data fitting of method of least squares. Applying this model, it is simulated on the computer that ring-down waveform changes with various cavity length maladjustments or mirror′s tilt, and the analyses is in good agreement with the experimental results. Results show, in order to improve metrical precision, it is suggested that ring-down signal on the oscillograph should be applied to adjust ring-down cavity. From the results, two kinds of criteria for cavity adjustment methods are proposed. One is that total figure of ring-down waveform should be applied to adjust cavity length maladjustments, the other is that mutuality of adjacent pulse should be applied to adjust cavity mirror' tilt.

This article carried theoretical analysis and experimental research on the scheme of remote sensing the minimum detection limit concentration for methane gas using a single laser source. In this project, the frequency-modulation (FM) and harmonic detection (HD) technologies are adopted. It is obtained through the theoretical calculation that the minimum detection limit concentration for methane gas was about 8.7×10-8 m. Simultaneously the experimental sensitivity of the detection system and the minimum measurable path-integrated concentration were measured to be 8.43×10-6 m/mV and 4.2×10-7 m respectively. This results show that the remote sensing system owns a super-high sensitivity and it can satisfy the need of monitoring methane in the coal mine.

It is well known that the fiber core refractive index control in fiber fabrication is important, especially for erbium doped fiber (EDF). The refractive index will affect the cutoff wavelength of EDF, and then will bring much impact on the gain performance of EDF. In this paper, the refractive index was measured and the composition of several EDFs was analyzed by electronic probe microbeam analysis (EPMA). The EDFs were fabricated through modified chemical vapor deposition (MCVD) method combining with solution doping technology. It was found that the aluminum codoping would seriously affect the ratio of silicon to germanium in the core, the more aluminum incorporated into the porous layer, the less germanium would stay in the EDF. It was explained with the two chemistry equations of alumina creation and germanium oxide volatilization. Codoping aluminum and germanium into silicate both would increase the refractive index, but index decreasing brought by the amount of germanium decreasing was larger than the index increasing brought by the amount of aluminum increasing, which led to the refractive index decreasing along with the amount of aluminum increasing.

Based on 4×4 and 8×8 optical switches and static wavelength converters in a novel optical switch matrix, a large capacity intelligent all-optical wavelength cross and converter connect (OWXC) is proposed. It can realize a low crosstalk and low delay zero-blocking probability for a link setup which can reduce cost to 30%. In the intelligent control software, a very simple control frame for control information transportation is proposed along with an optical link setup method by using three kinds of resource lock threshold to realize a classification of service (CoS) of link establishment. The experiment shows that the time from a link blocking to establishing is 22 ms. And it can realize automatic, self-automatic and human modes three link establishment methods. The whole cross capacity is 960 Gb/s with three fibers and 24 wavelengths and zero-blocking probability which is very useful for automatic switching optical network (ASON).