This PDF file contains the front matter associated with SPIE Proceedings Volume 9532, including the Title Page, Copyright information, Table of Contents, Invited Panel Discussion, and Conference Committee listing.

Dynamics of a laser-induced optical breakdown in the bulk of fused silica initiated by a sub-nanosecond laser pulse of an energy fluence as high as 8.7 kJ/cm² was investigated by using femtosecond time-resolved shadowgraphy. Plasma ignition, growth of the damaged region and accompanying hydrodynamic motion were recorded from the moment directly before the arrival of the driving laser pulse, in the time steps adapted to the rate of the occurring processes. The growth rate of the plasma channel, curvature radii and velocities of the wave fronts were extracted from the shadowgrams. It was found that the plasma channel develops with a supersonic velocity and the first observed shock front tends to transform itself from the initial bowl-like shape to the final spherical one characterising an acoustic wave. Appearance of multiple fronts accompanying the main shock front was registered and used in more detailed analysis of the optical breakdown dynamics in the transparent dielectrics.

For researching the influence factors of the damage threshold test results, the 1 on 1 test program and data processing on fused SiO2 optical elements was numerically simulated with Monte Carlo method. The influence of the surface defect density and the target test spots area for the test results of damage threshold was studied. The numerical simulation results indicate that the damage threshold of optical elements can't be accurately evaluated with 1 on 1 test program if the surface defects have the characteristics of both low density and low damage threshold. The zero-probability damage threshold isn't equal to the minimum energy density when the laser induced damage of optical element appears. This work is helpful for understanding the 1 on 1 test result and has important reference value in the actual damage threshold test of optical elements using 1 on 1 test method.

UV femtosecond laser pulse was used to excite the ultrafast carrier dynamics inside the Al₂O₃/SiO₂ high reflective mirror. Spectral shift between two different laser induced free electron absorption bands was observed. The former one centered at 406 nm undergo a fast decay of ~2.6 ps and a longer one of ~15 ps. Accompanied by the fast decay of the first absorption band, a new absorption band centered at 396 nm grew around ~2.8 ps after the laser excitation. The probable explanation the observed spectral shift of the free electron absorption band is that, the free carrier in the Al₃O₂ conductive band was trapped into some kind of defect state, which has an absorption peak at 396 nm, at a time scale of ~2.8 ps. Since the defect state has much longer lifetime than the initial generated free carriers in thee conductive band, probably under the condition of ultrafast high-frequency pulsed UV laser exposure, the incubation effect will decrease the laser damage threshold of the subsequent laser pulses.

Following three different types of high power lasers at Kansai Photon Science Institute are overviewed and controlling the laser damages in these laser systems are described: (1) PW-class Ti:sapphire laser for high field science, (2) zig-zag slab Nd:glass laser for x-ray laser pumping, and (3) high-repetition Yb:YAG thin-slab laser for THz generation. Also reported is the use of plasma mirror for characterization of short-wavelength ultrashort laser pulses. This new method will be useful to study evolution of plasma formation which leads to laser damages.

One of the most practical means of generating tunable mid-infrared output is by using cascaded parametric downconversion from 1 μm, where efficient and reliable high-energy nanosecond lasers are well established. The overall efficiency of the cascade relies heavily on the efficiency of the first down-conversion stage where it is beneficial to employ quasi-phase matched crystals such as periodically-poled Rb:KTiOPO₄ (PPRKTP). Ultimately, the pulse energy at 2 μm and the optimum design of the first cascade will depend on the maximum intensity which could be safely applied to these crystals and therefore these schemes mandate investigation of nanosecond laser-induced damage threshold in KTiOPO4 (KTP) and Rb:KTiOPO₄ (RKTP) at 1.064 μm and 2 μm. In the context of high-energy systems, where the beams are at most loosely focused, the limiting energy fluence will be determined by the laser induced damage threshold (LIDT) of the bare surface. Therefore the LIDT of the bare surface is the lowest LIDT which has to be taken into account in design of robust 2 μm parametric systems. We report surface LIDT measurements in KTP and RKTP with nanosecond pulses at 1.064 μm and 2.1 μm. We find that the reported LIDT for the bulk is far higher than that of the surface and therefore is unsuitable as a guide for the 2 μm parametric system designs. LIDT values for KTP and RKTP with nanosecond pulses at 2 μm have not been reported so far to the best of our knowledge.

Laser damage performance of large aperture optical components has been study under fourth harmonic of 1053nm Nd:glass laser irradiation (263nm).The threshold of optical components is very low under 263nm laser irradiation ,due to conversion of beam to higher energy photons of the quadrupled frequency (4ω), and is relative to material characteristic. A preliminary test of laser induced damage in fused silica (SiO₂) and CaF₂under 263nm laser is reported in this article. Thresholds of these two materials are obtained. Laser damage threshold of SiO₂ is found about 2 J/cm² by 1-on-1 method using pulsed 263nm laser, lower than CaF₂ whose threshold.

In this paper, metallic pulse compression gratings (MPCG) with three kinds of grating structures are manufactured. The diffraction efficiency and bandwidth of samples are measured and it can be found that the different grating structure has different diffraction efficiency and bandwidth. Laser damage tests of samples are implemented by an 800±30 nm laser at pulse duration of 31 fs and it can be also found that the different grating structure has different laser-induced damage threshold. Experimental measurements illustrate that the grating structure has a great influence on bandwidth, diffraction efficiency and damage threshold. The typical damage morphologies of MPCG reveal that the damage is induced by absorption and thermal stress.

In this paper, we investigated the effects of laser pulse width on laser-induced damage. We measured the damage threshold of K9 glass and UBK7 glass optical components at different pulse width, then analysis pulse-width dependence of damage threshold. It is shown that damage threshold at different pulse width conforms to thermal restriction mechanism, Because of cm size laser beam, defect on the optical component surface leads to laser-induced threshold decreased.

The laser induced damage to optics has been an issue of paramount importance in laser research community. The low damage threshold of fused silica surfaces predominantly restricts the development of high power and high energy systems. This paper is aimed at improving the surface damage threshold of fused silica substrates by researching the effect of mechanical and chemical defects on laser damage: cracks/scratches and metallic impurities. The cracks were found to close, at least in part, after thermal processing and the damage threshold of the indented region was little affected by the thermal processing. In contrast, the cracks were enlarged after chemical etching and the damage threshold was improved slightly. Concerning scratches, the damage threshold can be recovered significantly after different HF-based etching. The metallic contamination can be removed by HF-based etching and acid leaching. The etched surface shows that the damage threshold increased first to ~30J/cm² and then decreased with etching time while the damage threshold stabilized at ~30J/cm² for leaching >45min. The surface roughness may degrade after etching, from <1nm to 3~5nm RMS, but that is ~1nm after leaching. The leaching may be a potential method for dissolving metallic contaminants on the glass surface in order to get a smooth surface with high damage resistance.

Reducing contamination is essential for producing optical coatings with high resistance to laser damage. One aspect of this principle is to make every effort to limit long interruptions during the coating’s deposition. Otherwise, contamination may accumulate during the pause and become embedded in the coating after the deposition is restarted, leading to a lower laser-induced damage threshold (LIDT). However, pausing a deposition is sometimes unavoidable, despite our best efforts. For example, a sudden hardware or software glitch may require hours or even overnight to solve. In order to broaden our understanding of the role of embedded contamination on LIDT, and determine whether a coating deposited under such non-ideal circumstances could still be acceptable, this study explores how halting a deposition overnight impacts the LIDT, and whether ion cleaning can be used to mitigate any negative effects on the LIDT. The coatings investigated are a beam splitter design for high reflection at 1054 nm and high transmission at 527 nm, at 22.5° angle of incidence in S-polarization. LIDT tests were conducted in the nanosecond regime.

The dielectric crystals are important media for diverse optical applications due to their astonishing properties. Miniature photonic devices based on waveguiding structures have been incorporated in broad range of photonic devices that benefit from the excellent properties of crystals. We summarize our recent progress of research on the design and implementation of three-dimensional (3D) waveguiding structures in dielectric crystals by femtosecond laser inscription. With the engineering of the localized material modifications induced by femtosecond laser pulses, structures with on-demand geometries could be manufactured in dielectric crystals. The 3D photonic devices are designed and produced and the functions based on these 3D devices for beam splitting and waveguiding lasing are realized.

Scattering effect has great effect on machining morphology in sapphire processed by ultrashort pulse laser. On one hand, scattering leads to saturation of machining length despite the increase of pulse energy. On the other hand, scattering results in undamaged core in the elliptical damaged shell. When the laser intensity is above half the damage threshold, the electric field is scattered to 0 and doesn’t contribute to the laser intensity at latter position. The physical model which combines scattering effect, linear and nonlinear optical effects matches well with machining morphology of sapphire at different laser parameters, including pulse energies, focus positions, focal length and pulse duration. At first laser with lower pulse energy, for instance 25 μJ, processes the inner part of sapphire. During micromachining of sapphire, the focus positions move from the bottom to the top. At last the laser with higher pulse energy, 150 μJ for example, fabricates the surface. The objective lens with the focal length of 20 mm is suitable for machining sapphire and the optimal pulse duration is 950 fs.

The refractive indices of anisotropic (Lu_0.9Y_0.1)₂SiO₅ (LYSO) single crystal at different wavelengths have been measured by the minimum deviation method at room temperature. Its refractive indices decrease quickly with the increasing wavelength. Sellmeier dispersion equations were obtained by means of least square fitting, which can predict the refractive indices in transparent region. The dispersion behavior was also described by single-oscillator approximation with physical significance.

The paper reports synthesis and co-crystallization of 5 co-crystal of 4-nitrophenol (4N) with five different monoand diaminopyridines (4-aminopyridine (4AP); 3,4-diaminopyridine (34DAP); 2-amino-6-methylpyridine (26MAP); 2,6- diaminopyridine (26DAP); 2-aminopyridine (2AP)) resulted in five adducts with the molar ratio of components 2:1 in final compounds. X-ray analysis confirms the non-centrosymmetric packing of obtained compounds. Two compounds crystallize in the polar acentric P2₁ and three compounds crystallize in acentric orthorhombic Pna2₁ space groups. The comparative studies on the laser induced multiple and single shot damage thresholds of named crystals were carried out using radiation of 1064 nm from Nd:YAG laser with pulse width 10 ns. Obtained results show good laser-induced singleshot and multiple-shot damage threshold values for all studied co-crystals and are found up to 3.64 GW/cm² and 1.77 GW/cm² respectively.

Amount of energy deposited by a single, tightly focused nanosecond laser pulse in different transparent materials was measured vs. either the incident intensity or energy fluence. An integrating sphere enabled quantification of the energy scattered during the long-lived breakdown process. It was shown that absorptance dependence on the photon flux can be analytically described by the sigmoidal Hill function. We suggest using this analytical description to quantify empirical laser-induced breakdown threshold (LIBT). The structured changes in the breakdown area were analysed by the means of different kinds of microscopy, especially by the high-resolution-transmission- electron-microscopy (HRTEM). The analysis revealed nanocrystallisation in the densified material surrounding the void.

A high-efficiency pump-signal combiner for high power fiber amplifiers based on thermally expanded core (TEC) technique is reported in this paper. TEC technique is used to fabricate mode-field adapter which allows optimization of signal fibers in a monolithic (6+1) ×1 fiber combiner. The combiner is fabricated by connecting a tapered fiber bundle (TFB) to a passive 25/250 (NA=0.06/0.46) double-clad fiber (DCF). By this method, the coupling efficiency of SMF-28 signal fiber at 1064nm improves from 54% to 92.7%. The average pump coupling efficiencies of six 105/125 (NA=0.15) fibers are measured to be 96.7% at 976nm. Furthermore, the average signal transmission efficiency is around 93.3%. The fabricated fiber combiner is spliced to an Yb-doped DCF for use as an all-fiber amplifier. The slope efficiency is measured to be 71.6%.

Laser fluence and operational tempo of ICF systems operating in the UV are typically limited by the growth of laser- induced damage on their final optics (primarily silica optics). In the early 2000 time frame, studies of laser damage growth with relevant large area beams revealed that for some laser conditions damage sites located on the exit surface of a fused silica optic grew following an exponential growth rule: D(n) = D0 exp (n α(φ)), where D is final site diameter, D0 is the initial diameter of the site, φ is the laser fluence, α(φ) is the growth coefficient, and n is the number of exposures. In general α is a linear function of φ, with a threshold of φTH. In recent years, it has been found that that growth behavior is actually considerably more complex. For example, it was found that α is not a constant for a given fluence but follows a probability distribution with a mean equal to α(φ). This is complicated by observations that these distributions are actually functions of the pulse shape, damage site size, and initial morphology of damage initiation. In addition, there is not a fixed fluence threshold for damage sites growth, which is better described by a probability of growth which depends on site size, morphology and laser fluence. Here will review these findings and discuss implications for the operation of large laser systems.

Ultrashort-pulse laser excitation of dielectrics is an intricate problem due to the strong coupling between the rapidly changing material properties and the light. In the present paper, details of a model based on a multiple-rate-equation description of the conduction band are provided. The model is verified by comparison with recent experimental measurements of the transient optical properties in combination with ablation-depth determinations. The excitation process from the first creation of conduction-band electrons at low intensities to the formation of a highly-excited plasma and associated material fragmentation is explained by the model. For quartz samples, the optical properties are strongly influenced by self-trapped excitons, and the associated additions to the model are described.

We present a numerical model of internal modification in bulk borosilicate glass by high repetition rate picosecond laser pulses. We study free-electron dynamics, nonlinear energy deposition and thermal conduction. The optical absorptivity and modification regions both have good agreements with the experimental results. The smooth outer zone is the molten region and the inner-structure formation is caused by high-density free-electrons generated by thermal ionization. Excitation, relaxation and accumulation of free-electron density in the focal volume are analyzed using different pulse shapes and a double-pulse train. The deposited energy distribution and modification zone are controlled by pulse shaping.

We present characterization of structural modification triggered by tightly focused single pulses of a nanosecond laser inside single-crystal sapphire. Structural changes induced in the shock compressed region were investigated using high resolution transmission electron microscopy (HRTEM). Analysis of the zone around cavity in the bulk of sapphire reveals loss of crystalline order and formation of a mixture of amorphous/poly-crystalline structure. The properties of the laser-affected solid and possible routes of material transformation to the final state long after the pulse end is discussed. The results suggest that transformations to amorphous/poly-crystalline state occur as a result of sufficient heating of the shell region. This creates a localized molten zone which solidifies so rapidly that crystallization is by-passed.

Contaminations existing inevitably in high-power laser facilities modulate laser beams and decrease beam quality. This study set up a detection system to study the mechanism of initial filamentary damage in optical components induced by surface contaminations. The effect of ordinary solid particles, liquid particles, and solid-liquid mixed particles on the near-field intensity distribution of laser beam was studied and analyzed statistically. The experiment results show that pure solid particles make the beam generate diffraction rings with dark center usually in the shadow of the particles which is a weak intensity modulation; pure liquid particles focus the localized beam into a bright spot rapidly, but it is diffracted away soon; solid-liquid mixed particles cause diffraction rings with strongly bright center, but the high local intensity can be diffracted away only after a longer distance, which is one of the reason that induces the initial filamentary damage to optical components. The research results can predict the likelihood of component damage, and the corresponding preventive measures help to keep the safe operation of high-power laser facilities.

An optical parametric amplifier system pumped by 1 kHz, 8 mJ femtosecond laser pulses at 800 nm has been constructed to generate high intensity, infrared pulses (~ 3 mJ, 1400 nm, 40 fs) with a total conversion efficiency of ~ 40%. The femtosecond high intensity laser pulses at 800 nm and 1400 nm have been used for high order harmonic generation in a semi-infinitive gas cell and have allowed the achievement of bright phase-matched harmonic radiation in the extremeultraviolet and soft X-ray region.

Laser-induced damage is defined as any permanent laser-induced change in the characteristics of a sample. This change can be observed by many different inspection techniques, with different sensitivity, depending on the intended objectives and available techniques. The damage threshold definition and measurement are therefore very subjective and related to the detection method. The choice and implementation of a damage test system is then a critical issue on any experiment. In this work we present some implementation of detection techniques for laser damage metrology in the sub-picosecond regime. Different damage testing methods that have been applied will be discussed in view of their potential applications for testing functional optical components or to study physical process in the femtosecond regime, particularly the role of defects: optical microscopy, phase microscopy and time-resolved microscopy.

It is believed that the light emission induced by laser pulse gives some information on the damage initiation mechanics of fused silica. The laser induced fluorescence (LIF) of high purity fused silica irradiated by KrF laser is studied experimentally. LIF bands centered at 650nm of fused silica fused with surplus H₂ atmosphere was observed simultaneously with CCD and spectrometer in the cross direction of laser beam. Significant blue-shift of LIF is observed with the irradiation intensity increasing before laser induced breakdown. The technique to improve the signal intensity of LIF and the signal/noise ratio are discussed.

Al₂O₃ monolayer films were deposited on fused silica substrate and K9 glass substrate by electron-beam deposition. Annealing as a general post-treatment was used to enhance the quality of the Al₂O₃ coatings. The optical properties of the films were analyzed from the transmission spectra of the samples. The composition of the samples before and after annealing were measured by X-ray photoelectron spectroscopy (XPS). According to the analysis of the results, it can be found that the oxidation degree of the coatings increases after annealing in O₂ inside coating chamber. The laser-induced damage thresholds of the Al₂O₃ films can be increased after the annealing process. Finally, the damage morphologies of the Al₂O₃ coatings were analyzed.

Typical damage features of the silica films, prepared by the sol-gel and e-beam deposition methods, are investigated and compared under the irradiation of the single nanosecond pulse. The laser induced damage threshold of the sol-gel silica film is higher than that of e-beam deposited silica coating. The concentric surface structures are observed in all damage pits. Furthermore, the large scale mechanical delamination that is not from the film-substrate interface but from the inner of the film is interesting for the sol-gel silica coating, which is distinct from the explosive boiling that observed on the surface of the coating deposited by the e-beam deposition method.

We have designed and produced an optical coating suitable for broad bandwidth high reflection (BBHR) at 45° angle of incidence (AOI), P polarization (Ppol) of petawatt (PW) class fs laser pulses of ~ 900 nm center wavelength. We have produced such BBHR coatings consisting of TiO₂/SiO₂ layer pairs deposited by ion assisted e-beam evaporation using the large optics coater at Sandia National Laboratories. This paper focuses on laser-induced damage threshold (LIDT) tests of these coatings. LIDT is difficult to measure for such coatings due to the broad range of wavelengths over which they can operate. An ideal test would be in the vacuum environment of the fs-pulse PW use laser using fs pulses identical to of the PW laser. Short of this ideal testing would be tests over portions of the HR band of the BBHR coating using ns or sub-ps pulses produced by tunable lasers. Such tests could be over ~ 10 nm wide wavelength intervals whose center wavelengths could be tuned over the BBHR coating’s operational band. Alternatively, the HR band of the BBHR coating could be adjusted by means of wavelength shifts due to changing the AOI of the LIDT tests or due to absorbed moisture by the coating under ambient conditions. We conduct LIDT tests on the BBHR coatings at selected AOIs to gain insight into the coatings’ laser damage properties, and analyze how the results of the different LIDT tests compare.

Through a novel micro-processing mechanism in birefringent crystals proposed in this work, a coupler containing twin depressed cladding waveguides have been achieved in Nd:GdVO₄ laser crystals. By employing single-scan of femtosecond laser writing, twin tracks with different depths separated by a distance of 70μm were produced due to the birefringence of Nd:GdVO₄ crystal. The adjacent 30μm-diameter cladding waveguides, which consist of a 2×2 coupler with a separation of 70μm in a 4-mm-long crystal sample, were inscribed simultaneously. The ratio of output power division from both waveguides was approximately 10.5:1 at 633nm. Continuous-wave lasing was realized in the waveguide coupler platform under the direct optical pump at 808nm. This work indicates a great potential for femtosecond laser inscribed symmetry structures such as waveguide couplers in birefringent crystals based on the proposed micro-processing mechanism.

Surface shape of optical components is an essential factor of the laser beam quality. Different types of surface correspond to different characteristics of the laser focal spot. Striated surface shape is one of common and typical cases of optical component surfaces in laser facilities, which have attracted great attention. For learning the impact of the component on focal spot in the far-field, a model component with the similar features was introduced in the study. Intensity distributions of focal spot in the far-field was simulated after laser beam went through the model component. Effects of the modulation depth and the modulation period on spot morphology were presented. Furthermore, the relations between these optical specifications and focal spots with some requirements had been analyzed. The results can enhance our understanding about striae degrees of optical elements and have reference values to guide the processing and the use of large-aperture components correctly.

With the development of holography technique and nano-superfinishing technique, holography grating has being used into the spectrometer. To overcome some drawbacks of optical system for traditional plane and concave grating typed spectrometer, a splitting-light optical system for spectrometer based on volume phase holographic transmission (VPHT) grating is designed and developed in this paper. Meanwhile, the principle of VPHT grating is introduced by using the coupled-wave theory, and the relationship between the diffraction efficiency of the VPHT and the grating depth and the irradiation wavelength are simulated by means of MATLAB numerical computing method. In order to validate this splitting-light optical system, the experiment of measuring spectral resolution is performed and the spectral resolution reached 2nm, a calibration equation between the diffraction wavelengths and the shift of the corresponding wavelengths is obtained by using polynomial fitting algorithm. The experimental results demonstrate that the design of the splitting-light optical system for spectrometer based on VPHT grating is feasible.

Photoacoustic spectroscopy (PAS) is a hybrid, well-established and promising detection technique that has widely applied into a lot of fields such as bio-medical, material and environment monitoring etc. PAS has high contrast and resolution because of combining the advantages of the pure-optical and the pure-acoustic. In this paper, a photoacoustic experiment of glucose solution induced by 532nm pumped Nd:YAG tunable pulsed laser with repetition rate of 20Hz and pulse width of 10ns is performed. The time-resolved photoacoustic signals of glucose solution induced by pulsed laser in the average time of 512 are obtained. And the photoacoustic experiments of different concentrations of glucose solutions and different wavelengths of pulsed laser are carried out in this paper. Experimental results demonstrate that the bipolar sine-wave profiles for the time-resolved photoacoustic signal of glucose solution are in good agreement with the past reported literatures. And the different absorbing coefficients of glucose solution can be gotten according to the slope of the first part of the time-resolved photoacoustic signals. In addition, the different acoustic velocities of glucose solution can also be gotten according to the shift change of the time-resolved photoacoustic peak values. Research results illustrate that the characteristic wavelengths, different optical and acoustic properties of glucose solution can be interpreted by the time-resolved and peak-to-peak photoacoustic signals induced by the pulsed laser.

The multilayer ridge metal/multilayer-dielectric gratings (MMDGs) for pulse compressors show high efficiency, broad bandwidths, large fabrication tolerances and high laser-induced damage thresholds. The diffraction efficiency, bandwidth, and near-field distribution of the multilayer structure ridge MMDG are theoretically investigated. Simulation results show that the film structure of the grating ridge has a great influence on the bandwidth and near-field distribution. The maximum electric field is located in the high-index layer of the grating ridge with high -1st diffraction efficiency. As the thickness of the high-index layer decreases, the maximum electric field moves to the low-index layer of the grating ridge with. Base on the results, the sandwich ridge MMDG is an ideal pulse compression grating for chirped pulse amplification systems.

The result shows that the fusing atmosphere and heat treatment process have different affluence on the laser induced damage threshold (LIDT) by 355nm and 248nm laser pules. As for the fused silca, the atmosphere and the temperature during the fuseing and heat treatment process contributes to the changing of structure and micro-composition. For high power 355nm laser pules, the affluence of H₂ during the fusing process is benefical to reduced the destructive probability, the LIDT-values is about 20-22.2 J/cm²; But for the 248nm laser pules ,the highest LIDT-values is about 8-10J/cm² of the fused silca fused with surplus O₂ atmosphere. In order to improve the laser damage character, the heat treatment process is one of the effective way for the fused silica. We have investigated the peculiar heat treatment process with O₂ atmosphere by 1100℃ can boost the LIDT to 28.2 J/cm² and 13 J/cm² by 355nm and 248nm laser pules, while the process time is not as long as better.

A polymer coating was designed and prepared to modify the surface of CIP to match the hardness of KDP, and deliquescence removal was explored by addition proper water online. The above techniques not only weaken the mechanical scratches and increase removal rate, but also are beneficial for subsequently cleaning. Removal function exhibits particular transitional zone on the edge of finishing spot which clearly demonstrates the existence of different processing mechanisms simultaneously. The figure accuracy and PSD1 of a large-aperture KDP are apparently converged after MRF.

Fused silica is widely used in high-power laser systems because of its good optical performance and mechanical properties. However, laser damage initiation and growth induced by 355 nm laser illumination in optical elements have become a bottleneck in the development of high energy laser system. In order to improve the laser-induced damage threshold (LIDT), the fused silica optics were treated by two types of HF-based etchants: 1.7%wt. HF acid and buffer oxide etchant (BOE: the mixture of 0.4%wt. HF and 12%wt. NH₄F), respectively, for varied etching time. Damage testing shows that both the etchants increase the damage threshold at a certain depth of material removal, but further removal of material lowers the LIDT markedly. The etching rates of both etchants keep steady in our processing procedure, ~58 μg/min and ~85 μg/min, respectively. The micro-surface roughness (RMS and PV) increases as etching time extends. The hardness (H) and Young’s modulus (E) of the fused silica etched for diverse time, measured by nano-indenter, show no solid evidence that LIDT can be related to hardness or Young’s modulus.

To enhance the performance of the Insulated Gate Bipolar Transistor (IGBT), sub-microsecond laser annealing (LA) is propitious to achieve maximal dopant activation with minimal diffusion. In this work, two different lasers are used as annealing resource: a continuous 808 nm laser with larger spot is applied to preheat the wafer and another sub-microsecond pulsed 527 nm laser is responsible to activate the dopant. To optimize the system’s performance, a physical model is presented to predict the thermal effect of two laser fields interacting on wafer. Using the Finite-Element method (FEM), we numerically investigate the temperature field induced by lasers in detail. The process window corresponding to the lasers is also acquired which can satisfy the requirements of the IGBT’s annealing.

The structure properties of random mask of antireflective structure prepared by the thermal dewetting process are investigated. As a low-cost and large-scale technique, the mask obtained in our work has a great prospect in the field of solar cell and high power laser system. Ultrathin films of amorphous Ag are deposited on the fused silica by magnetron sputtering. By fast thermal annealing the structures in Ag film are agglomerated on the substrate and form mask. The influence of different thickness and annealing temperature on the structure properties of random mask are studied. The surface morphologies are characterized by scanning electronic microscopy. The suitable conditions to obtain excellent quality Ag nanomasks with the pebble particles are achieved.

Hafnia-silica (HfO₂/SiO₂) mixed thin films with a wide range of different compositions have been deposited on fused silica substrate by E-beam co-evaporation. The change in composition is achieved by changing the deposition rates of individual materials. The transmittance spectra are measured by the spectrometer, and then the refractive indexes are calculated with Essential Macleod. The vertical uniformity and grain structure of the films are analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), respectively. The experimental results demonstrate that the coatings have good uniformity, and all the films are amorphous except the pure HfO₂ film. In addition, the mixed coating with about 16.85% SiO₂ content has a higher refractive index than the pure HfO₂ coating.

A lot of optical components with large aperture are employed in high-power solid-state laser driver. These optical components are with high requirement on the surface shape, optical homogeneity and stress distribution. In order to test these parameters, different types of interferometers, surface profilers and stress meters from different manufacturers are needed. But the problem is the products from different manufacturers may provide different test results. To solve the problem, the research and verification of the key measurement technologies of large aperture optical components are carried out in this paper. The absolute flatness and optical homogeneity measurement methods are analyzed. And the test results of different interferometric software are compared. The test results from different surface profilers and stress meters are also compared. The consistency and reliability of different test software are obtained with the comparing results, which will guide users to select a suitable product.

It is surface imperfections on optical elements that have significant effects on the propagation quality of light in the high power laser systems, and even cause laser damage on the optical elements. Thus, quantitative detection of surface imperfections is very important for optical elements quality evaluation. The microscopy imaging method has been widely applied to detect surface imperfections. In the process of acquiring image, image background brightness could be non-uniform owing to uneven light intensity of illumination. Thus, some extracted information of surface defects will be lost. To solve the problem, a background correction method based on mathematical morphological is proposed. Luminance means, luminance uniformity, standard deviations and image detail as four factors are used to evaluate imperfection image. The background correction method combined with the improved Otsu method is used to extract the target of surface defects, which has better performance than the basic Otsu method. Through the research of the sensitivity of the algorithm for image noise and segmentation accuracy, it can offer theoretical directions for quantitative detection of surface imperfections.

Photovoltaic cell is one of the most important components of laser powered unmanned aerial vehicle. Illuminated by high power laser beam, photovoltaic cell temperature increases significantly, which leads to efficiency drop, or even physical damage. To avoid such situation, the temperature of photovoltaic cell must be predicted precisely. A dynamic thermal model of photovoltaic cell is established in this paper, and the relationships between photovoltaic cell temperature and laser power, wind speed, ambient temperature are also analyzed. Simulation result indicates that illuminated by a laser beam, the temperature of photovoltaic cell rises gradually and reach to a constant maximum value. There is an approximately linear rise in photovoltaic cell temperature as the laser flux gets higher. The higher wind speed is, the stronger forced convection is, and then the lower photovoltaic cell temperature is. But the relationship between photovoltaic cell temperature and wind speed is not linear. Photovoltaic cell temperature is proportional to the ambient temperature. For each increase of 1 degree of ambient temperature, there is approximate 1 degree increase in photovoltaic cell temperature. The result will provide fundamentals to take reasonable measures to control photovoltaic cell temperature.

This study success to smaller and control the diameter of single mode optical fiber whispery gallery mode (WGM) to diameter 0.8 mm nonetching and nontaping treated. The sensitivity of this type ultra-small U-shape WGM strengthens neither etching nor taping fibre. The sensitivity we apply to thermo test depends on wavelength shift from 40 ~ 96°C (R² = 0.99 ). The specially characteristics of the optical fiber could be tested for temperature, refraction, vibration, concussion, and CO₂ detection.

Transparent composite Lutetium aluminum garnet (LuAG) ceramics were successfully synthesized by thermal diffusion bonding method. Three isothermal holding temperature of 1450°C, 1600°C, 1780°C for 10h under vacuum were used to study the changes of bonding interface morphology, Optical microscope, SEM and laser interferometer (GPI-XP,zygo) study show that diauxic growth of grain interface appears when the thermal bonding holding temperature increased. The sintering mechanism of diauxic growth of grain interface during the thermal diffusion bonding was also discussed using diffusion theory. The diauxic growth of grain interface provides us the possibility to get high quality composite laser ceramics as we designed.