Hologram Recording in Various Glass Plates by Corona Charging

We propose techniques of hologram replication in glass plates and reconstruction on another film by corona charging. A surface relief hologram on an azobenzene polymer film was recorded in the form of electric polarization in glass plates that include alkali cations by corona charging at high temperature. The hologram recorded in the glass plate is stable for more than 1 month at room temperature. After removal of the azobenzene polymer film from the plate, poly(methyl methacrylate) (PMMA) film was spin-coated onto the plate. The hologram recorded in the plate was reconstructed with the same surface relief structure on the PMMA film by corona charging again at 110°C.     

Application of Surface Relief Hologram Using Azobenzene Containing Polymer Film

Surface relief holograms are fabricated by irradiation of laser interference patterns on an azobenzene polymer film. The hologram needs no post-treatment, and can be erased by heating the films to above its glass transition temperature. Rewritable Fresnel holograms are fabricated on azo-polymer film. Replication of the surface relief hologram is also demonstrated. An application for business cards is considered.     

紫外光致聚合物和制造镭射玻璃的技术

本文论述了制造镭射玻璃的技术和材料。技术包括：清洗玻璃板；将紫外光致聚合物材料涂到玻璃板上；将镭射玻璃母版粘贴到涂有光致聚合物的玻璃板上；紫外光曝光固化；丝网印刷；真空镀膜；涂保护层。紫外光致聚合物材料是由光引发剂、单体、预聚体和其它添加剂组成。实验结果表明：此种镭射玻璃具有很高的抗酸、碱、热和紫外照射的能力     

Numerical Analysis of Photoinduced Surface Relief Grating Formation by Particle Method

The time evolution of photoinduced surface relief grating formation on azobenzene polymer films is analyzed by particle method for fluid mechanics. The surface relief grating is grown by using two beams interference with various polarization states numerically and compared with experimental results. The force acted on the dipole by electromagnetic field and surface force are considered as the driving force for photoinduced mass transport. The improved surface tension model is proposed in order to calculate curvature coefficient. The numerical results are coincided with experimental results qualititatively.     

Direct Fabrication of Surface Relief Holographic Diffusers in Azobenzene Polymer Films

We propose a direct fabrication of light diffusers using azobenzene polymer films. Holographic recordings of surface relief diffusers are formed on the polymer film by exposure to an Nd:YAG laser (532 nm) through source diffusion materials. No post-treatment is needed, and it can be erased by heating or irradiating uniform laser beam. Diffusion pattern can be controlled by the polarization of the laser. Transmittance of over 88% is obtained at the wavelength of 633 nm.     

电晕充电多孔PTFE/PP复合驻极体过滤材料的电荷存储特性

报道采用电晕充电方法，对用高温熔融粘合工艺制备得到的双向拉伸多孔PTFE与PP复合过滤材料进行驻极体改性，并采用热刺激放电和表面电位测量等方法研究了材料的电荷存储稳定性,根据驻极体相关理论，对实验结果进行了解释. 结果表明，电晕充电的多孔PTFE/熔喷或纺粘PP覆膜材料中，既存在空间电荷又存在极化电荷，复合膜的界面是电荷陷阱的主要来源. 从不同面对复合膜材料进行充电时，材料具有完全不同的电荷存储特性. 由于材料体内空间电荷和极化电荷的极性相反、相互补偿，表面电位测定并不能真正反映材料内部电荷的存储状态. 关键词： 驻极体 电晕充电 聚合物复合膜 热刺激放电     

Gain enhancement in Nd:glass laser amplifiers using electro-polished aluminum reflectors

This paper presents a comparative study of single pass gain of a Nd:glass laser amplifier using geometrically identical reflector cavities of different reflector materials or surface treatment. An improvement in the small-signal single-pass gain by a factor of 2 and 1.5 is observed for an electro-polished aluminum cavity over a gold-plated cavity and mechanically polished aluminum cavity, corresponding to an increase of 25% and 15% respectively in the pump coupling efficiency.     

Deep subsurface optical waveguides produced by direct writing with femtosecond laser pulses in fused silica and phosphate glass

In the present work, we have analyzed the use of elliptical beam shaping along with low numerical aperture focusing optics in order to produce circular cross-section waveguides in different materials at large processing depths by direct femtosecond laser writing (100 fs, 800 nm, 1 kHz). A variable slit located before the focusing optics allows to generate a nearly elliptical beam shape and also to reduce the effective numerical aperture of the beam along the shat axis of the ellipse. The focusing optics allows to focus the beam deep inside the sample, which is translated at a constant speed transversely to the writing beam direction. The influence of several experimental parameters (energy per pulse, slit width, processing depth) on the properties of the produced waveguides has been analyzed. The influence of the intrinsic properties of the material (refractive index, composition) has been analyzed by comparing results obtained in fused silica and Er:Yb co-doped phosphate glass. The results obtained show that this approach leads to the successful production of deep subsurface (up to 7 mm) waveguides with circular cross-sections. Preliminary results using chirped pulses in the phosphate glass suggest that temporal pulse shaping can be used as an additional parameter to optimize the guided mode symmetry.     

Beam characterization and spatial coherence measurement of F2 laser using Lumilass glass fluorescence

This paper presents the spectral emission and saturation properties of a Lumilass G9 fluorescence glass excited using a 157 nm laser emitting ∼10 ns duration pulses. This fluorescence glass can be applied in conjunction with a CCD array for beam profiling and divergence measurements. This method can also be used for deriving information on the spatial coherence function of the F₂ laser. This constitutes one of the major contributions of the paper and is also discussed.     

激光二极管抽运氦气冷却钕玻璃叠片激光放大器热致波前畸变和应力双折射的数值模拟和实验研究

热效应仍是限制激光放大器向高功率、高光束质量进一步发展的瓶颈问题, 高效的热管理是抑制热效应的重要技术途径. 研究了基于激光二极管抽运氦气冷却的钕玻璃叠片激光放大器的热效应. 利用有限元数值模拟的方法, 分析了钕玻璃的温度、应力应变和应力双折射分布, 并计算了热致波前畸变和退偏损耗, 与实验结果符合得较好, 在热沉积为0.7 W/cm³的条件下, 6片钕玻璃总的热致波前畸变为6.77λ , 最大退偏量大于90%.     

基于可调谐二极管激光吸收光谱技术的密闭玻璃容器中水汽浓度及压力的探测

冻干法处理过的药品瓶中残存的水汽(H₂O)是药品变质的主要影响因素之一, 如何快速准确地测量瓶中的水汽浓度及压力, 是检测药瓶是否泄漏的关键. 本文报道了利用1.39 μm半导体激光器作为光源, 结合波长调制吸收光谱技术, 实现了对密闭玻璃容器(药瓶)中水汽浓度及压力的探测, 并通过转台模拟生产线对系统在动态条件下的性能进行了测试. 研究结果表明, 在0.2%-12%的H₂O浓度范围内真实值与测量值之间的相关度和标准偏差为0.9978 和4.81%, 在0.1-100 atm (1 atm=1.01325×10⁵ Pa)的压力范围内两者之间的相关度和标准偏差为0.982和5.6%, 系统对应的压力及浓度的最低检测限约为2.5 Torr (1 Torr=1.33×10² Pa)和400 ppm. 通过利用转台以及Labview编写的快速在线处理软件进行了动态条件下的测试, 一分钟可以处理300个左右的药瓶, 可以很好地满足快速实时探测的要求. 该方案可以直接应用于药瓶在线检测, 并且使用2台激光器可以实现多组分同时探测分析(如H₂O、氧气等).     

Effect of laser irradiation on the structure and valence states of copper in Cu-phosphate glass by XPS studies

The effect of laser irradiation using three different wavelengths (IR, visible and UV) generated from Nd:YAG laser on the local glass structure as well as on the valence state of the copper ions in copper phosphate glass containing CuO with the nominal composition 0.30(CuO)-(0.70)(P₂O₅), has been investigated by X-ray photoelectron spectroscopy (XPS). The presence of asymmetry and satellite peaks in the Cu 2p spectrum for the unirradiated sample is an indication of the presence of two different valence states, Cu²⁺ and Cu⁺. Hence, the Cu 2p_3/2 spectrum was fitted to two Gaussian-Lorentzian peaks and the corresponding ratio, Cu²⁺/Cu_total, determined from these relative areas clearly shows that copper ions exist predominately (>86%) in the Cu²⁺ state for the unirradiated glass sample under investigation. For the irradiated samples the symmetry and the absence of satellite peaks in the Cu 2p spectra indicate the existence of the copper ions mostly in Cu⁺ state. The O 1s spectra show slight asymmetry for the irradiated as well as unirradiated glass samples which result from two contributions, one from the presence of oxygen atoms in the P-O-P environment (bridging oxygen BO) and the other from oxygen in an P-O-Cu and PO environment (non-bridging oxygen NBO). The ratio of NBO to total oxygen was found to increase with laser power.     

钕玻璃、Nd:YAG和Nd:GGG热容激光特性比较

考虑固体热容激光器对工作介质的要求,对比分析了掺钕的玻璃、YAG和GGG的多种材料性能。并对三者在激光工作周期内的瞬态温度场及热应力进行了数值模拟。结果表明:在给定的边界及工作条件下,当钕玻璃激光器以热容方式工作,时间为5 s时,介质最高升温超过400 K,最大热致应力为25 MPa,接近其断裂极限的50%。在此条件下进行冷却,当水温为283 K时,需经过约120 s才基本恢复到初始工作状态。而Nd：YAG和Nd：GGG两种介质在相同输入工作条件下,工作时间可达10 s,且温度分布相对平坦,温差和热应力较小,经水冷约30 s可恢复到初始状态。但模拟计算中,发现Nd：YAG在冷却阶段的最大应力达77 MPa,已超过断裂阈值下限值的50%。兼顾冷却时间、材料所能承受的应力及晶体生长尺寸,以及实现100 kW的平均功率输出等因素,Nd：GGG晶体是目前三者中比较适合于作为高平均功率、重复率热容方式工作的激光材料。     

Experimental investigation and metallographic characterization of fiber laser beam welding of Ti-6Al-4V alloy using response surface method

In the present study, experimental investigations of fiber-laser-beam-welding of 5 mm thick Ti-6Al-4V alloy are carried out based on statistical design of experiments. The relationship between the process parameters such as welding power, welding speed, and defocused position of the laser beam with the output responses such as width of the fusion zone, size of the heat affected zone, and fusion zone area are established in terms of regression models. Also, the most significant process parameters and their optimum ranges are identified and their percentage contributions on output responses are calculated. It is observed that welding power and speed plays the major role for full penetration welding. Also, welding power shows direct effect whereas welding speed shows the inverse effect on the output responses. The bead geometry is influenced by the defocused position of the laser beam due to the change in power density on the workpiece surface. However, overall fusion zone area is unaffected. Mechanical characterization of the welded samples such as microstructural analysis, hardness, and tensile tests are conducted. It is noticed that the hardness value of the FZ is higher than the HAZ and BM zone due to the difference in cooling rate during welding which promotes the formation of α′ martensitic phase in the FZ. Also, an average hardness value in the FZ is compared for two different defocusing positions (i.e. 1 and 2 mm). It is found that hardness value is higher for 1 mm defocused position than 2 mm due the decrement in grain size below a critical range at 2 mm defocused position. The ultimate tensile strength and % elongation of the welded samples are degraded as compared to BM which can be further improved by post heat treatment.     

Surface texturing of the carbon steel AISI 1045 using femtosecond laser in single pulse and scanning regime

Surface texturing of the metals, including steels, gained a new dimension with the appearance of femtosecond lasers. These laser systems enable highly precise modifications, which are very important for numerous applications of metals. The effects of a Ti:sapphire femtosecond laser with the pulse duration of 160 fs, operating at 775 nm wavelength and in two operational regimes - single pulse (SP) and scanning regime, on a high quality AISI 1045 carbon steel were studied. The estimated surface damage threshold was 0.22 J/cm² (SP). Surface modification was studied for the laser fluences of 0.66, 1.48 and 2.37 J/cm². The fluence of 0.66 J/cm², in both working regimes, induced texturing of the material, i.e. formation of periodic surface structures (PSS). Their periodicity was in accordance with the used laser wavelength. Finally, changes in the surface oxygen content caused by ultrashort laser pulses were recorded.