光折变晶体的热透镜效应

通过对光折变晶体的热透镜效应的理论分析发现,光通过光折变晶体时,只有在晶体发生双折射的前提下,才能发生热透镜效应。并指出,晶体内存在的由热效应引起的横向各向异性温度梯度仅是产生热透镜效应的一个方面,而“光阻”则是产生光折变晶体热透镜效应的另一个原因,从而丰富了光折变效应的内涵。     

PbS纳米微粒溶胶热光系数dn/dT的测量和光束限制效应研究

利用单光束Ｚ扫描技术测量了ＰｂＳ纳米微粒溶胶的热光系数ｄｎ／ｄＴ和热致折射率ｎ_２，研究了在连续激光源作用下的光限幅效应,并对实验结果进行了分析与讨论. 关键词：     

基于有限元的平面光波导粘接热应力分析

基于有限元理论对阵列光纤和波导芯片粘接情况进行了建模与仿真,分析了在温度变化下不同粘接区域厚度的热应力和微位移的产生和分布,结果表明粘接界面的边缘区域对温度变化最敏感.根据光弹效应定性分析了粘接区域的应力双折射,并利用光束传播法计算了由此微位移所导致的光功率损耗,结果表明若以附加损耗小于0.15dB的标准考察,则必须要求粘胶厚度的理论值在16μm以内.总结了温度变化和在相同条件下不同粘胶厚度对平面光波导封装性能的影响规律.     

基于有限元的平面光波导粘接热应力分析

基于有限元理论对阵列光纤和波导芯片粘接情况进行了建模与仿真,分析了在温度变化下不同粘接区域厚度的热应力和微位移的产生和分布,结果表明粘接界面的边缘区域对温度变化最敏感.根据光弹效应定性分析了粘接区域的应力双折射,并利用光束传播法计算了由此微位移所导致的光功率损耗,结果表明若以附加损耗小于0.15 dB的标准考察,则必须要求粘胶厚度的理论值在16 μm以内.总结了温度变化和在相同条件下不同粘胶厚度对平面光波导封装性能的影响规律.     

四棒串接连续灯泵浦Nd:YAG大功率激光器

 报道了一种符合工业应用的四棒谐振腔连续Nd:YAG激光器。实验中采用对称放置方式四棒串接谐振腔得到2 105 W的平均功率输出，光束参数积24 mm·mrad，系统总光电转换效率达到3.5%。还对影响激光器工作的因素进行了理论分析。     

激光二极管侧抽运双棒串接准连续Nd:YAG高功率绿光激光器

研制一台激光二极管(LD)侧面抽运双棒串接准连续Nd:YAG折叠腔高功率绿光激光器,理论分析了热致双折射效应对系统的影响,并对用石英旋转片补偿前后的情况进行模拟对比.在考虑了补偿后的情况下设计了热稳定谐振腔.实验中采用两个串接的由30个20 W的LD阵列侧面抽运的Nd: YAG棒和Ⅱ类临界相位匹配HGTR-KTP晶体.在抽运电流均为21.6 A,重复频率为27.2 kHz时.获得了最大平均输出功率为164 W.脉冲宽度为130 ns的532 nm绿光输出,光-光转换效率为13.7%,测得光束质量因子为M2x=9.52,M2x=9.86,不稳定度为2.3%.实验结果显示.经补偿后的激光系统能在宽的稳区范围内稳定运转.     

飞行光学导光系统中的空气热透镜效应

研究了激光加工用大功率ＣＯ２激光束在飞行光学导光系统中传输所产生的空气热透镜效应。实验发现当飞行光学导光系统中的空气静止时将产生空气热透镜效应,而充以一定压力的压缩空气却可以消除空气热透镜效应,实验表明无热透镜效应时,光束遵循高斯光束传输规律,而秀热透镜效应时,光束偏离高斯光束的传输规律,并影响到激光束聚焦焦点的大小和位置。另外通过激光空气热透镜效应的非线性模型计算了热透镜效应所引起的光束传输相对     

光学材料热光系数的精确测量——“热光系数仪”

本文介绍用于光学材料系数精确测量的“热光系数仪”。该仪器采用两种干涉仪组合、微机控制和数据采集处理等设计方案,实现了高精度测量。低温区热膨胀系数α、折射率温度系数β热光系数W的测量精度可达±3×10~(-7)°C~(-1)。     

LD端面泵浦Nd∶YAG激光器中的热透镜焦距

采用热透镜焦距的理论计算与实验测量相比较的研究方法，得到一种端泵固体激光器出激光时的在线测量方法.通过建立热透镜等效腔模型以及腔型分析求解得出腔内光束束腰半径,用刀口法测出DPL腔外的远场发散角,根据发散角与透镜变换前后的束腰关系，得出LD端面泵浦Nd∶YAG激光器中的热透镜焦距.结果表明,通过上述方法所得结果与理论计算的热透镜焦距吻合,证实此方法准确、可行.     

双折射晶体激光传输的热光效应与电调制机理

本文基于多物理场数值仿真平台COMSOL的RF射频模块,通过有限元法求解电磁场频域分析方程,求解了高斯激光在双折射晶体中的传输问题,重点分析了波长,温度和外加电场强度对o光e光离散角和e光波形的影响。研究结果表明温度升高使得离散角变小,接收屏上e光波形向左偏移,而Z方向外加电场强度正向增大则会使o光e光离散角增大,接收屏上e光波形向右偏移。上述研究结果验证了通过改变外加电场来调节温度影响的可行性,为设计一种消除温度效应的光信号调制装置提供了理论依据和基础。     

Investigation of the beam propagation in a pumped laser rod

A method investigating the beam propagation in a pumped laser rod is proposed. In this method, the pumped laser rod in a resonator is evenly divided into N segments along the laser rod axis, and each segment is considered as a small thermal lens with thermal focus length of f. Accordingly, the beam radius distributions in the laser rod for the symmetric and asymmetric resonators are thus calculated, respectively. The beam radius distribution in the whole resonator is also calculated. Moreover, the calculated beam distribution in the whole resonator and in the rod is also described in detail.     

Beam quality considerations of high power Nd:YAG lasers

High power Nd:YAG lasers with fiber optic beam delivery have introduced new capabilities for material processing applications. Here, we present the stable resonator design for high power Nd:YAG lasers to optimize beam quality for fiber optic transmission. Dependence of beam parameters on position and dioptric power of thermal lens has been investigated and optimized to achieve efficient fiber optic beam delivery. With the optimum resonator configuration, an efficient fiber optic beam delivery over the entire operating range of input power has been achieved. The results of stable resonator design with good beam quality and output power have been presented.     

Compensation of the thermally induced depolarization in a double-pass Nd:YAG rod amplifier with a stimulated Brillouin scattering phase conjugate mirror

Stimulated Brillouin scattering phase conjugate mirrors (SBS-PCMs) are extensively used to compensate the phase distortion of active media in a high-energy laser system with double-pass amplification. However, the depolarization loss from the thermally induced birefringence of the active medium by a photoelastic effect cannot be avoided despite the uses of phase conjugate mirrors. In this work, the depolarization loss in a double-pass Nd:YAG rod amplifier with a SBS-PCM has been studied with Jones matrix calculations. In addition, the depolarization ratios and the leak beam patterns are obtained experimentally and theoretically for four possible optical schemes. Both experiment and theoretical results show that depolarization is effectively compensated when a Faraday rotator is located after the amplifier.     

Thermal effects in high-power Nd:YAG disk-type solid state laser

An investigation of thermal effects in a high-power Nd:YAG disk-type solid state laser pumped with different pump beam transverse profiles is carried out by numerical simulation based on the finite element method (FEM). Impact of the heat sink on the thermal effects is included in the simulation. The distribution of first principle stress, thermally induced birefringence, including the distribution and variation of the birefringence loss, are studied. The characteristics of the phase variation are analyzed with consideration of the temperature gradient, deformation, strain and thermal stress. Thermal lensing is explored as a function of pump power and of the radius pumped with different pump beam transverse profiles. The non-parabolic part of optical phase distortion is simulated. Furthermore, the characteristics of the bi-focus of the disk laser are also studied. Experiments on the maximum tensile stress distribution and depolarization loss are carried out. The presented calculations are in qualitative agreement with the experimental observations.     

Laser and thermo-optical investigations of Nd:YAG ceramics

The ‘wet’ technology was implemented for processing of Nd:YAG ceramics. The samples of disk, rod, slab shapes with 1–2% Nd dopant were fabricated and tested. Several method of optical characterization were applied. Near 80% transmission and scattering losses <0.2 cm⁻¹ were demonstrated. The laser action with 34% slope efficiency was obtained for the best case. To characterize the spatial inhomogeneities of output parameters “half-microchip configuration” with output coupler formed by uncoated output facet of plane parallel ceramic sample was implemented. Thermally induced aberrations and birefringence observed in Nd:YAG ceramic of disk samples under high heat load were examined and compared with numerical models.     

The dynamic stability resonant cavity design of two rod Nd:YAG laser

The stability of the higher output power with high-quality beams is very important parameter in material processing. This paper presents using the S parameter and Gauss beam parameters matching to design efficient resonant cavity of two-rod Nd:YAG. The fundamental mode beam radius in rod, fundamental mode beam radius on the mirror, beam quality factor, and the value of the degree of the symmetry of the TEM00 mode volume as a function of the between neighbor rods distance, laser rod end face to mirror distance, and input power are simulated. The design method of resonant cavity is illustrated and compared with previously published experimental measurements for different pump power and the length of the cavity parameters and a good agreement has been found.     

A Flash-Lamp-Pumped Nd:YAG Laser with Dual-Telescopic Optics Configuration

A flash-lamp-pumped Nd:YAG laser that contains two laser rods and dual-telescopic elements is investigated theoretically and experimentally. The two intracavity telescopes of the resonator are appropriately chosen and adjusted to achieve a large-volume TEM₀₀ mode inside the laser rods, and to minimize the variational effects of the thermal lens in the rods. The drift of the optimal operating point of the resonator caused by variation in the pump energy is compensated by adjusting defocusing of the two telescopes over a broad pump energy range. It is experimentally shown that our resonator geometry with appropriate parameters obtained the output energy of 560 mJ with 100 #x03BC;s duration and slope efficiency of 3.5#x0025;, at a pump energy of 16J, even though the misalignment tilting angle of the end mirror reached #x00B1;5mrad. The bi-focusing effect caused by the thermally-induced stress birefringence was compensated by a 90#x00B0; quartz rotator. Output energy was increased by 18#x0025; at the pump energy of 16J. The misalignment tilting angle of the end mirror with intracavity telescope was 4 times larger than that without intracavity telescope.     

Nd:YAG薄片激光器热致波前畸变

 理论分析了激光二极管端面泵浦薄片Nd:YAG 激光器的激光介质热效应对波前相位分布的影响,给出了薄片激光器波前热畸变的计算公式。数值模拟了理想均匀泵浦及4阶超高斯泵浦下的波前分布,分析了介质厚度和泵浦均匀性与波前畸变量的关系。研究表明,介质越薄,激光泵浦光均匀性越好,泵浦功率密度越小,激光波前畸变越小;与介质厚度、泵浦功率密度相比,泵浦光光强分布对波前的影响更为显著。     

LD端泵下Nd∶YAG端面形变热效应研究

用计算机模拟了在不同的泵浦光分布和不同的泵浦功率下其端面形变的大小.主要对具有轴对称性的泵浦光和沿竖直方向为高斯分布,水平方向为均匀分布的长条形泵浦光在不同的功率下所引起的端面形变进行了计算机模拟.所采用的方法是先对温度场进行理论计算,建立理论模型.然后,对形变进行理论计算,并用计算机模拟了形变.得到了形变导致的端面形变热透镜焦距与致热功率之间的关系曲线,目的在于进一步研究由于端面形变所引起的热效应.