This PDF file contains the front matter associated with SPIE Proceedings Volume 8206, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

We demonstrate three-dimensional (3D) microstructuring inside glass by ultrafast laser to fabricate microfluidic chips integrated with some functional microcomponents such as optical attenuators and optical waveguides. The fabricated microchips are applied to understand phenomena and functions of microorganisms and cyanobacteria. Ultrafast laser irradiation followed by thermal treatment and wet etching in dilute hydrofluoric acid solution resulted in fabrication of 3D microfludic structures embedded in a photosensitive glass. The embedded microfludic structures enabled us to easily and efficiently observe Phormidium gliding to the seedling root, which accelerates growth of the vegetable. In addition, integration of optical attenuators and optical waveguides into the microfluidic structures clarified the mechanism of the gliding movement of Phormidium. We termed such integrated microchips nanoaquariums, realizing the highly efficient and functional observation and analysis of various microorganisms.

The paper summarizes the recent progress on the optical materials and components for the high power laser system in China. The amplifier material, Nd glass, has been developed with continuous melt. Non-linear crystals, KDP/DKDP, have been grown with rapid and traditional growth method. Fused silica and K9 glass has been achieved high quality. Some potential materials for next generation high power laser system are also evinced in this summary.

Laser-induced fluorescence (LIF) of high-purity fused silica irradiated by ArF excimer laser is studied experimentally. LIF bands of the fused silica centered at 281nm, 478nm and 650nm are observed simultaneously. Furthermore, the angular distribution of the three fluorescence peaks is examined. Microscopic image of the laser modified fused silica indicates that scattering of the generated fluorescence by laser-induced damage sites is the main reason for the angular distribution of LIF signals. Finally, the dependence of LIF signals intensities of the fused silica on laser power densities is presented. LIF signals show a squared power density dependence, which indicates that laser-induced defects are formed mainly via two-photon absorption processes.

The ability of a UV laser to modify surface properties of quantum well (QW) microstructures that would lead to formation of a "defective layer" is of particular interest to the process of QW intermixing (QWI). We discuss the results of surface and interface study of InGaAs/InGaAsP QW microstructures capped with InP and a 243-nm thick layer of SiO_2-x that were irradiated with a KrF excimer laser delivering up to 25 pulses at 124 mJ/cm². The optical quality of SiO₂ films remains relatively unaffected by the irradiation with the KrF laser operating in the investigated window of parameters. The x-ray photoelectron spectroscopy experiments point out the negligible role of SiO_2-x in out-diffusion of matrix atoms that would enhance the QWI process. However, the KrF laser was found to significantly modify the interface between UV transparent SiO_2-x and the InP layer. Our results suggest that the resulting layer of the altered material promotes out-diffusion of atoms and intermixing in the QW region.

Experimental and theoretical progress on subpicosecond laser pulse breakdown in dielectric films is reviewed. The single pulse threshold fluences can be related to fundamental material properties and scaling laws with respect to pulse duration and material bandgap. Multiple pulse thresholds are controlled by native and laser-induced defects. A phenomenological model is introduced which describes the accumulation and relaxation of such defects. The model is able to explain the experiments and can be used to assess relevant defect parameters. Experimental results are presented that exemplify how the ambient atmosphere affects the multiple-pulse laser damage thresholds.

As an important part of almost all laser systems, optical film is so fragile that easy to damage because of temperature rise. Based on temperature field theory and thermal conduction equation, the physical model of temperature field of multiplayer films illuminated by Gaussian laser is built. By solving the Maxwell equation, the average energy flow rate of plane wave with unit intensity propagation through the films is obtained. The numerical calculation program of the temperature field of multiplayer films illuminated by 1064nm laser is built using alternating direction-implicit technique. The simulation results show that laser spot radius, heat exchange coefficient, laser power and film material have a great effect on the temperature field of multiplayer films. These are the key factors to damage the optical films. The results obtained in this paper would be both theoretical basis and reference for optical thin film components developing.

Particle stacking structured SiO₂ porous films were prepared by sol-gel method. A model has been established to analyze the heat conductivity of these films. It is assumed that the heat energy mainly transfers through particles and their contact points. In particle stacking structured materials, a particle contacts with twelve contiguous particles, and forms twelve heat conduction branches. This model is suit to the conditions that: the size of particles in the porous material is uniform; heat conductivity of particle skeleton is much greater than particle clearance; and all contact area between particles approximately equal. The results show that: heat conductivity of particles stacking porous material is anisotropic, material heat conductivity depends on that of the particle skeleton and the ratio between radiuses of particle contact area and particle itself.

HfO₂ single layers and HfO₂/SiO₂ high reflectors with standard 1/4 wavelength design were prepared by ion assisted deposition (IAD) with APS ion source and ion beam sputtering (IBS). Characterization of HfO₂ single layers such as structural and optical properties, surface topography and absorption have been studied. The laser-induced damage thresholds (LIDTs) of the high reflectors with different multilayer stacks at 1064nm were tested with S-on-1 testing mode according to ISO-11254. In addition, optical properties, surface topography and absorption of these testing high reflectors have also been investigated in our experiments. All the results used to analyze the LIDTs of high reflectors have been discussed and interpreted in literature.

Coupling effect between 355 nm laser and 1064 nm laser in damage initiation and morphology formation are investigated on two different coatings prepared with Hf/SiO₂ and HfO₂/SiO₂ respectively. It was found that materials had little influence on the couple effect. When extra 1064 nm pulse energy is low, 355 nm laser induced damage thresholds of both coatings increase because of laser conditioning and then when 1064 nm pulse energy is high enough, 355 nm LIDTs decreased. Damage morphologies are also studied to explore the damage mechanism at respective wavelength. For the entirely different electric field distribution, 355 nm laser induced damages are mainly from nanometer-sized absorbers at upper interfaces while initiators for 1064 nm laser locate at substrate-coating interface or substrate subsurface. Under simultaneous illumination, the sensitive defects are still the precursors, but the damages are more catastrophic compared with damages induced by 355 nm laser only and they also show representative damage characteristics induced by single laser, namely 355 nm laser induced small pits and 1064 nm laser induced large delamination. Further studies also show that delamination area grows with the increase of pit numbers induced by 355 nm laser at fixed 1064 nm laser fluence. A possible mechanism was proposed to interpret observed delamination area growth phenomenon.

Nb₂O₅ thin films at various cathode power and substrate bias voltages were deposited by pulsed DC reactive magnetron sputtering of a metallic Nb target in a pure oxygen atmosphere. The characteristics of the films have been studied using spectrometer, atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM). Laser damage tests at 1064 nm wavelength with pulse duration of 12 ns were conducted on the single-layer systems. Results indicate that the cathode power may not be an important impact-factor of the LIDT of Nb₂O₅ thin films but substrate bias voltage has significant influence on the laser resistance of Niobium oxides films. The maximum laser induced damage threshold (LIDT) of 28.8 J/cm₂ was obtained for the film deposited at substrate bias voltage of -60V.

Micro-defect is one of key limiting factors in the improvement of the laser-induced damage threshold (LIDT) of thin films. In the present paper, thin films were prepared using the electron-beam evaporation technique with different coating materials and pre-melting processes. The relationships of thin film LIDT with impurity element content and with pre-melting processes were investigated. The experiment results indicate that a number of impurity elements play an important role in the LIDT of the samples. An efficient pre-melting process is necessary to maintain deposition stability, which could also reduce micro-defect density in thin films.

The multilayer dielectrics (MLDs) for broad bandwidth 800nm pulse compression gratings were fabricated with optimized design by electron beam evaporation using three different kinds of materials (Ta2O5/SiO2/HfO2), which had more than 99% reflectance with bandwidth larger than 160nm around the center wavelength of 800 nm and high transmission at the exposure wavelength of 413nm. Laser-induced damage behaviors of the mirrors were investigated. It was found that the laser-induced damage threshold (LIDT) of the samples could reach 1.0J/cm2 and 2.0J/cm2 in the normal beam (57 degrees, TE mode) at pulse duration of 50fs and 120fs, respectively. The depth information of the damage sites at these two cases was explored by atomic force microscope (AFM). The reason of the sample having so high LIDT was also discussed in this paper. The MLDs provide a solid base for the high laser threshold 800nm pulse compression gratings and may open a new way for broad bandwidth 800nm reflectance coatings used in the ultrashort pulse laser system.

In this paper, porous nanostructures on BK7 glass were manufactured by chemical treatment in order to obtain antireflection (AR) components with improved laser damage resistance. The damage-resistant properties of the samples with nearly 100% transmittances at three pulsed laser wavelength were investigated. The damage tests showed that the BK7 glass with AR nanostructures can achieve the LIDTs of 58J/cm², 20 J/cm² and 12 J/cm² under the irradiation of 12ns 1064nm pulses, 10ns 532nm pulses and 8ns 355nm pulses, respectively. These values are much higher than those of AR coated glasses, but are almost the same level of un-etched substrate. The effect of structural properties on electric field distribution of porous surface was investigated by a three-dimensional (3D) finite difference time-domain (FDTD) model. The simulation results and the morphology of damage site on porous glass are compared to those of un-etched surface, and are discussed to reveal the possible damage mechanism. Finally, some possible solutions to improve the LIDT are proposed.

Laser damage performance of K9 glass and fused silica glass were tested respectively at same experimental condition with 1064 nm nanosecond laser. The initial damage threshold (IDT), the damage growth threshold (DGT) and the damage growth laws of the two optics glass were investigated comparatively. The results show that the damage growth behavior of the two glasses are quite different, for example, the lower damage growth threshold and the higher damage growth coefficient for K9 glass, which can attribute to the difference of the material's damage morphology, optical absorption, residual stress near damage site between the two optics glass. The research is very important to choose transparent optical material applied in high power laser.

In high-power laser system, in order to extend the components' service life and reduce the operation costs, more attentions should be pay at the research for damages ablation at multi-layer optical components and other high load optical components. 240ps, 35ps, 6ps 1053nm laser pulses has been used to investigate damage ablation and damage resistant experiments at 0° high reflection films. By comparing the damage morphology and damage resistant threshold of the ablation pits at different pulses width, it was superior to use ultra-short pulse to repair multi-layers optical components. It was found that the shorter pulse width has been used, the higher the damage resistant threshold and the lower the laser modulation. Furthermore, the finite-difference time-domain method was used to simulate the electric-field intensification within the large size damage region of multilayer films.

This paper is devoted to a long-term investigation into the nature of incubation effect of multilayer dielectric HR mirror coatings. Accumulated damage behaviors of HfO₂/SiO₂ mirrors for 800nm, 1053nm, and 1064nm, both fabricated by conventional electron beam evaporation (EBE), were investigated by ultra-short pulse (800nm/~100fs), short pulse (1053nm/~1ps), and long pulse (1064nm/~10ns) lasers, respectively. Incubation effect was found to be a universal phenomenon for HfO₂/SiO₂ mirrors irradiating by the femto-nanosecond lasers. And when the shot number was about 100, the multi-pulse damage threshold of samples decreased to the level of 60~70% of the single-pulse threshold. Typical damage morphologies and depths information of HR samples were characterized by optical microscope and surface profiler. The results revealed that the electric field distribution within the mirrors had significant influence on the initial damage onset of the mirrors. In addition, theoretical simulation was carried out to describe the incubation behaviors of HfO₂/SiO₂ mirrors in the femto- and nano-second regions. It seemed reasonable that incubation effect was attributed to the accumulation of native or laser-induced electronic trapping states.

As an important optical element, beam sampling grating (BSG) is used in the terminal of inertial confinement fusion (ICF) drivers. It can provide a very slight sampling beam for the precision diagnosing of laser energy and wavefront distortion. However, in practice, its non-uniform diffraction efficiency seriously influences the accurate signal of sampling beam, and finally affects diagnostic ability. BSG is usually fabricated by holographic ion beam etched (HIBE) process. In this paper, a mechanical polishing processing technology was used to improve uniformity of the diffraction efficiency of BSG after HIBE. In the processing, cerium oxide (CeO₂) was used to polish the local areas of grating where exhibit higher diffraction efficiency with the purpose of changing the depth of grating profile, and then they have similar efficiency with the surrounding areas. By iteration of the above process, BSG finally achieve the improved uniformity of diffraction efficiency over the area of a 430 x 430 mm². The RMS of diffraction efficiency of BSG after mechanical polishing shows great reduction down to 4.8% as compared with that of the as-polished RMS of 21%. The effects of this processing on laser damage was characterized by the measuring the LIDT for the laser radiations of 355nm.

The laser induced damage threshold (LIDT) of fused silica samples was investigated with laser damage testing setup (355 nm, 6 ns). A new model, which improved the theory of defect-induced damage, was proposed to describe the multiple-defect coupling effect of the nanosecond-pulsed laser induced damage. The correlation between the damage probability and the damage threshold of this model was also reported.

Subsurface damage (SSD) in optical components is known to play an important role in restricting the high fluence operation in high power laser systems. Subsurface damage appears inevitably during the shaping, grinding, and polishing process, which are essential in the production of defect-free optical components. In order to obtain expectant optical components, we need to obtain the distribution and character of fractures in the subsurface region introduced during fabrication process, and therefore investigate the positions and depths of the SSDs in the processed optical components accurately and remove them ultimately. In this study, we made several groups of samples of fused silica with different surface roughness, and manage to detect the positions and depths of the SSDs via Total Internal Reflectance Microscopy (TIRM). The lateral distribution of the SSDs is obtained. The surface etched in fluoride solution exposing subsurface damage is also observed. The character of fractures in the subsurface region is discussed.

Silicon is a key material to electro-photonic detectors, which makes the studies of laser induced damage of silicon significantly important in laser detecting and military applications. The damage characters of silicon under high-intensity nanosecond laser pulses have been investigated in this paper. The results show that the synergy of thermal, shock and spectral radiation effects of laser plasma determines the damage characters in silicon. Due to thermal and shock effects of laser plasma, the material is melt, vaporized, ionized and pushed out in laser irradiated area. This way, pits are formed and the cool ejected effluents are distributed radially. The interference between scattered and incident laser can form a periodic structure because of the periodic distribution of thermal stress in particular area. N, O and Si characteristic spectrum in laser plasma suggests that colored film is the mixture of SiO_x:SiN_y from laser plasma under repetitive laser pulses.

We report the experiment results of the study on dust pollution initiated damage in optical component of the ICF facility and evaluate the influence of this kind damage on other optical component. Dust caused by laser-induced damage in optical component in vacuum environment at the high power laser facility was collected with fused silica flat optics. The transmission change of the dust polluted optics was observed and analyzed. The damage probability of the dust polluted optics was tested by s-on-1 method using pulsed Nd-YAG solid laser. Results showed that dust polluted sol-gel anti-reflection film coated fused silica optics exhibited lower transmission and higher damage probability than the naked fused silica flat optics. Besides, the dust particle on the input surface will cause severer damage than on the output surface.

The 355 nm laser-induced damage thresholds (LIDTs) of polished fused silica with and without the residual subsurface cracks were explored. HF based wet etching and magnetorheological finishing was used to remove the subsurface cracks. To isolate the effect of subsurface cracks, chemical leaching was used to eliminate the photoactive impurities in the polishing layer. Results show that the crack number density decreased from~10³ to <1cm^-2, and the LIDT was improved as high as 2.8-fold with both the subsurface cracks and the polishing layer being removed. Subsurface cracks play a significant role in laser damage at fluencies between 15~31 J/cm² (355nm, 8ns). HF Etching of the cracks was shown to increase the damage performance as nearly high as that of the samples in which subsurface cracks are well controlled.

We have investigated ablation process of silica glass induced by X-ray irradiation. X-rays around 100 eV were generated by irradiation of Ta targets with Nd:YAG laser light. The laser plasma soft X-rays have a pulse duration of 10 ns. The soft X-rays were focused on silica surfaces at up to 10⁸ W/cm². We found that silica glass can be ablated by X-ray irradiation. Typically, the ablated surface have a roughness of 1 nm after ablation by 500 nm in depth. Further, trenches with a width of 50 nm can be clearly fabricated on silica surface. Thus, high quality, practical micromachining can be achieved by the X-ray technique. It is remarkable that more precise features can be fabricated on silica surface than the thermal diffusion length. The results implies non-thermal ablation process. We observed ions ejected from silica surfaces during the irradiation and found that ions are almost atomic species such as Si⁺, O⁺, Si₂⁺, O₂⁺, SiO⁺. The results revealed that silica surfaces are broken into atomic species by X-ray irradiation. Among X-ray ablated species, 0.5-15 % are estimated to be ionized. Even though 0.5 % atoms are ionized in silica surface, the energy density of Coulomb repulsive force is higher than the energy density of binding energy of silica glass. Therefore, we can conclude that Coulomb repulsion between X-ray generated ions are essential for X-ray ablation of silica glass.

To reduce manufacturing costs and to improve electrical efficiency of solar cells are top priorities of the whole photovoltaic (PV) industry. The success of laser processing techniques in the integrated circuits industry indicates that such techniques could also be adapted in the PV industry. In this paper, we presented recent progress in advanced laser processing for manufacturing of high efficiency silicon solar cells at RX Technologies, especially the application of picosecond laser pulses for ablation and doping on crystalline silicon solar cells. A system based on this technique has been employed in production line by one of the leading manufacturers of solar cells. Efficiencies of 19.2% and 17.5% for monocrystalline silicon and polycrystalline silicon have been achieved under the condition of volume production. This result shows a great improvement, compared with results obtained from traditional manufacturing techniques.

We have developed a novel method for efficient structuring of the surface of materials by applying femtosecond near infrared laser pulses simultaneously with a weak extreme ultraviolet beam, which leads to a very strong radiation-matter interaction and brings a dramatic increase of the surface processing speed. We present our recent experimental results on surface nanostructuring of thin films of amorphous carbon and polymethyl methacrylate deposited on bulk substrates and discuss the underlying physical mechanisms. In the case of amorphous carbon, large areas of laser-induced periodic surface structures with a spatial period of 550 nm were created, having their origin in laser-induced convective currents. Our method provides a powerful tool for fast modification of tribological properties of the irradiated sample.

Different strategies of the laser induced deflection (LID) technique for direct and absolute absorption measurements are presented. Besides selected strategies for bulk and coating absorption measurements, respectively, a new strategy is introduced allowing the transfer of the LID technique to very small samples and to significantly increase the sensitivity for materials with a very weak photo-thermal response. Additionally, an emphasis is placed on the importance of the calibration procedure. The electrical calibration of the LID setup is compared to two other approaches that use either doped samples or highly absorptive reference samples in combination with numerical simulations. Applying the LID technique, we report on the characterization of AR coated LBO crystals used in high power NIR/VIS laser applications. The comparison of different LBO crystals shows that there are significant differences in both, the AR coating and the LBO bulk absorption. These differences are much larger at 515 nm than at 1030 nm. Absorption spectroscopy measurements combining LID technique with a high power OPO laser system indicate that the coating process affects the LBO bulk absorption properties. Furthermore, the change of the absorption upon 1030 nm laser irradiation of a Nd:YVO₄ laser crystal is investigated and compared to recent results. Finally, Ytterbium doped silica raw materials for high power fiber lasers are characterized with respect to the absorption induced attenuation at 1550 nm in order to compare these data with the total attenuation obtained for the subsequently manufactured laser active fibers.

Laser induced damage in optical material in nanosecond regime is widely attributed to local precursors in range of nanometer to micrometer size. The damage precursors nature strongly depends on materials (coatings, non linear crystals, substrates,..), breakdown location (bulk, surface, interface) and irradiation parameters (wavelength, pulse duration...). The weakness of knowledge on parameters as sizes, densities and natures of precursors, let think that the choice of the diagnostic method which reveals laser damage has to be adapted to each situation of irradiation. Concerning the LIDT determination, destructive methods are usually involved: we can cite full size test using the "real" final configuration of irradiation, raster scan method using a focused laser beam allowing laboratory test and statistic approach allowing study with different beam sizes in order to probe the material homogeneity in terms of precursors. This multi-scale approaches give relevant information on material properties regarding high power laser irradiation. In order to investigate the laser damage initiation mechanisms, it appears necessary to involve non-destructive diagnostics. These diagnostics permit to highlight modifications linked to precursors before material breakdown. The main difficulty here is the local character of the diagnostic added to the low density of initiating center. A multi-scale approach is thus also well adapted to the non-destructive case. Interest of diagnostics as local fluorescence and photothermal deflexion both correlated with LIDT results will be discussed. To illustrate the purpose, examples on non linear crystals and coatings will be shown.

In this paper, a new wavelet threshold denoising algorithm has been proposed based on the correlation characteristics between layers coefficient and the inner-layer coefficient. For each wavelet coefficient, a corresponding threshold is constructed according to the wavelet coefficients between layers and layer-related features. The experimental results show that the ability of this algorithm is better than the traditional algorithm in the aspect of image denoising.

A filtered optical feedback cavity ring down (FOF-CRD) technique employing a continuous wave Fabry-Perot diode laser is employed to measure the total optical losses, i.e., absorption and scattering in optical components with arbitrary thickness. The FOF from the ring down cavity (RDC) is re-injected into the oscillator cavity of the diode laser, and the coupling efficiency of the laser into the RDC is significantly enhanced due to the FOF effect. An optical component having parallel optical surfaces is inserted exactly normal to the light beam in the RDC. The optical losses of the component are obtained from the change in the ring-down time of the RDC containing the component with respect to that of the empty RDC. The measurement results for different samples are in good agreement with conventional laser calorimetry data. The experimental results have demonstrated that the FOF-CRD technique is simple, inexpensive and fast for measuring optical losses of optical components used in high-power laser system.

Fluorescence microscopy is a useful tool to image defect nanostructures in the bulk of dielectric materials. The application of microscopy with laser-induced fluorescence on optics to detect the damage of optical films was explored. A fluorescence image system was built that incorporated in-situ damage testing capabilities. The experimental results was checked under an ex-situ Nomarski microscope.

Due to the limits of experimental conditions the laser damage test is confined to small area sample. By small area damage test, some characteristics of the material can be obtained in qualitative. But the test result of the small area damage testing cannot represent the performance of the material illuminated by large scale high power laser whose typical scale is usually more than 250mm in diameter. Statistical approach is an important method to extrapolate the data of small area test to predict large area performance to create the damage probability curve of large scale illuminated material. In this article, we represent a revised statistical representation of the damage probability which can be more useful to do the extrapolation. A simulation based on the Monte Carlo method is also given to simulate the accuracy and reliability of the extrapolation results.

Principles that enable to synthesize anisotropic laser ceramics have been established. Anisotropic laser ceramics contain micro domains made of anisotropic crystals, and we have invented the novel alignment technology of micro domain structure in laser ceramics assisted by rare-earth trivalent. Our novel process is essentially superior to the traditional electromagnetic processing from the viewpoint of mass production. We discussed the significance of anisotropic laser ceramics, and we also show the result of evaluations to our orientation controlled RE:FAP ceramics.

With the purpose of investigation on the visible emission properties of Tm³⁺ ions, a Tm³⁺-doped Y₂O₃ transparent ceramic was fabricated by sintering at 1800 °C for 20 hour with a vacuum degree of 1x10^-3 Pa. 3 at% ZrO₂ was introduced as the sintering aid and the average grain size was measured to be 22 μm. The optical transmittance of the ceramic achieved 76.3 % at 1 μm. The PL spectra at room temperature and low temperature were measured under 361 nm excitation. The ~453 nm emission bands were observed and the luminescence mechanisms were discussed. It was found that the Tm: Y₂O₃ transparent ceramic have the potential to be used in white LED packaging structure.

The relationship between optical scattering losses and microstructure, especially inside pores distribution, was studied in transparent Nd:YAG and Yb:YAG ceramics. Specimens with different transmittance values were fabricated by vacuum sintering from 1730°C to 1760°C for 30 to 50 h through a solid-state reaction method. Light scattering losses were calculated from transmittance values measured by UV-Vis-IR spectrophotometer. Micromechanism, including inside pores and grains on etched surfaces, was characterized via high magnification optical microscope. The porosities were also counted in microscope observation. Curves of the relations between scattering losses (or transmittances) and porosities were obtained. In addition, the genesis of inside pores and the process of exhaust were discussed in this paper.

Composite YAG/2.0at%Nd:YAG transparent ceramic was fabricated by solid-state reactive sintering a mixture of commercial α-Al₂O₃, Y₂O₃, and Nd₂O₃ powders with tetraethoxysilane (TEOS) and MgO as sintering additives. A fully dense YAG/2.0at%Nd:YAG ceramic with an average grain size of ~20μm was obtained by vacuum sintering at 1750°C for 50h. There are almost no pores or second phases present at grain boundaries or inner grains. The in-line transmittance reached 83.6% at the lasing wavelength of 1064nm and 82.0% at 400nm. The porosity of the sample was at the level of several vol ppm. The composite YAG/2.0at%Nd:YAG transparent ceramics are promising to generate high-energy laser.

La₂O₃, Y₂O₃, ZrO₂, and MgO+TEOS were added as the sintering aid to prepare Yb³⁺:Y₃Al₅O₁₂ transparent ceramics. Pre-calcination was adopted to improve the crystalline quality and morphology of the commercially available Y₂O₃ raw powders. The non-stoichiometricaly doped La₂O₃, Y₂O₃, and ZrO₂ enhanced the grain boundary mobility so fast that abnormal grain growth occurred and pores tended to be enclosed in these grains. It was found that MgO+TEOS had a positive effect on full densification of the Yb:YAG ceramics. The grain boundaries moved moderately so that pores could be eliminated well and meanwhile the grains would not get too large. Laser output experiment was also carried out for the Yb:YAG transparent ceramics.

In this study, 30 at% Er:RETaO₄ (RE = Sc, Y, Gd, Lu) polycrystalline powders were synthesized by the solid-state method. Their structures were determined by the Retvield refinement to X-ray powder diffraction. The optical spectra of the trivalent erbium ions in monoclinic RETaO₄ (RE = Sc, Y, Gd, Lu) polycrystalline powders was investigated by absorption and emission measurements at room temperature. Under the excitation of 970 nm laser, the green photoluminescence of ²H_11/2, ⁴S_3/2→⁴I1_5/2 were observed. The 1 μm and 1.5 μm infrared emissions were also surveyed. The fluorescence decays of Er³⁺ from the multiplets ⁴S_3/2 and ⁴I1_3/2 were studied at room temperature. It is found that the decay curves from the multiplet ⁴S_3/2 exhibit a non-exponential behavior, which may be due to cross-relaxation processes. At the same time, we investigated that the 2.8μ (due to the transition ⁴I_11/2→⁴I_13/2) luminescence spectra excited by 808 nm laser.

Highly doped Er³⁺:GdTaO₄ crystal was grown successfully by the Czochralski(CZ) method for the first time. The crystal structure was determined by Rietveld refinement to X-ray powder diffraction. The absorption and photoluminescence spectra at room temperature were investigated. The Judd-Ofelt transition intensity parameters Ω_t (t=2, 4, 6) were fitted to its absorption spectrum. With parameters Ω_t, the oscillator strengths, fluorescence branching ratios, transition probabilities and the lifetimes of Er3+:GdTaO4 were calculated. The near-infrared and mid-infrared fluorescence properties were also analyzed and discussed. The results show that the Er³⁺:GdTaO₄ crystal may be regarded as a potential solid-state laser material for 2.6μm.

Yb³⁺-doped Rare Earth Stannates Ln₂Sn₂O₇(Ln=Y, Gd) with space group Fd3m were synthesized by co-precipitation technique. Their structures were determined by Rietveld refinement to their X-ray diffraction, and their atom coordinates, lattice parameters and temperature factors were given. From emission, absorption and excitation spectra, the energy levels of Yb³⁺ in Ln₂Sn₂O₇(Ln=Y, Gd) were assigned and the crystal field parameters were fitted to energy splitting of Yb³⁺-doped Ln₂Sn₂O₇ (Ln=Y, Gd).

In this paper, DKDP crystals with deuterium content of 55%, 65% and 70% were grown by the traditional temperature-reduction method. The property including lattice constant, transmittance spectra, Raman spectra, conoscopic image, and laser damage threshold (LDT) were measured. The results showed that with increasing the degrees of deuteration for DKDP crystals, the value of lattice parameter a (b) increases and the transmittance also increases in the range of 350-1800 nm while the laser damage threshold (LDT) decrease. For DKDP crystals, the spectra of Raman scattering split into two parts and the peak intensity of the totally symmetric PO4 vibration decrease compared with that of KDP crystals. The homogeneity of the DKDP crystals has not obvious difference.

This paper shows DKDP crystals of different deuterium content are cut for type I non-critical phase-matching with the direction at 90° to the crystal Z axis (θ=90°) and at 45° to the crystal X axis (Φ=45o), and are measured at the FHG experiments with fundamental frequency wavelength 1064nm and 1053nm, respectively. The optimum deuterium content of DKDP crystal, that can achieve non-critical phase-matching at FHG experiments, is confirmed by measuring the relationship of deuterium content and phase-matching angle.

Large size of YCa₄O(BO₃)₃(YCOB) crystals were grown both by Czochralski and Bridgman methods. Large size elements as large as 60 mm clear aperture were cut and polished with surface flatness of 1/5 wavelength. Optical homogeneity of YCOB crystal was found in the order of 10^-6. Laser damage thresholds of several YCOB crystal elements were tested using different laser facilities with different pulse widths or wavelengths, with thresholds varied from 0.8 GW/cm² to more than 1 TW/cm². One SHG and two optical parametric chirped-pulse amplification (OPCPA) experiments were executed to characterize the nonlinear optical properties of YCOB crystals and the quality of the crystals. The results shown that YCOB had good performance in OPCPA application, especially with low content of parameter florescence. Combined with good NLO performance and possibility to grow large size crystals, YCOB crystal was a good choice for high power OPCPA applications.

The crucial problem of DKDP crystal for third harmonic generation (THG) is its low laser-induced damage threshold with respect to KDP, which greatly limits energy fluence of the output laser and crystals' useful life. In order to study the relation between wavelength and laser-induced damage of DKDP, we carried out some related experiments in present work. DKDP crystal was conventionally grown from 80%-deuterated solution of high pure materials and the crystal was cut to tripler sample of type II. Laser-induced damage threshold of DKDP crystal for THG was measured under different wavelengths and the effect of laser annealing was also investigated. The experiment shows that laser annealing could obviously improve laser-induced damage threshold of DKDP crystal. The threshold is improved to 1.4, 1.9 or 2.7 times that before annealing for fundamental, second or third harmonic, respectively. Thus laser annealing is an effective approach to enhance laser-induced damage resistance of DKDP crystal.