共查询到20条相似文献,搜索用时 62 毫秒
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固体激光器向高平均功率发展存在的最大问题是沉积在激光介质里的废热。废热的消除将导致热透镜、机械应力和退偏等效应,并由此造成光束质量的退化,激光功率的降低,甚至可能造成介质的断裂。采用薄片激光器设计可以允许介质具有高的泵浦功率密度而不产生显著的温度梯度,当泵浦区尺寸远大于薄片厚度时,热流可认为是沿厚度方向的一维分布。合理设计泵浦耦合结构,可以使薄片径向温度分布近似均匀,从而大大降低介质的热透镜效应和热致应力双折射。因此薄片激光器可以定标放大到很高的平均功率。 相似文献
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理论分析了隔离器在高功率多模激光入射时的自退偏特性.结果表明:线性双折射致退偏与圆双折射致退偏均与入射光功率的平方成正比,线性双折射致退偏与光斑大小无关,而圆双折射致退偏随光斑半径的增大而减小.当光斑半径与旋转晶体半径相比很小时(R0/r0≥80)圆双折射引起的退偏大于线性双折射引起的退偏,当光斑半径接近旋转晶体半径(R0/r0≤3)时,与线性双折射引起的退偏相比,圆双折射引起的退偏可以忽略.对比单模激光入射,在同种条件下,多模入射使得线性双折射致退偏减小了0.4倍, 最小圆双折射致退偏减小为0.05倍. 相似文献
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理论分析了隔离器在高功率多模激光入射时的自退偏特性.结果表明:线性双折射致退偏与圆双折射致退偏均与入射光功率的平方成正比,线性双折射致退偏与光斑大小无关,而圆双折射致退偏随光斑半径的增大而减小.当光斑半径与旋转晶体半径相比很小时(R0/r0≥80)圆双折射引起的退偏大于线性双折射引起的退偏,当光斑半径接近旋转晶体半径(R0/r0≤3)时,与线性双折射引起的退偏相比,圆双折射引起的退偏可以忽略.对比单模激光入射,在同种条件下,多模入射使得线性双折射致退偏减小了0.4倍, 最小圆双折射致退偏减小为0.05倍. 相似文献
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对LD泵浦的掠入射板条放大器链系统激光介质的热效应进行研究。针对掠入射放大器结构建立了相应的热力学模型,对激光介质的温度场分布、热致波前畸变和热透镜效应进行了详细的理论分析。利用有限元分析软件COMSOL模拟了晶体内部的温度、应力及应变的分布情况,并进一步讨论了板条厚度、泵浦尺寸以及种子光入射角对光程差和热透镜造成的影响。结果表明,随着泵浦光斑尺寸和种子光入射角的增大,光程差变小,热透镜效应减弱;板条厚度对光程差和热透镜的影响较小。模拟计算结果对于预测板条热效应的强弱、热效应的补偿,以及放大器链结构参数的设计提供了依据。 相似文献
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Second harmonic generation (SHG) was observed in PbO-B2O3 glasses after heat treatment at elevated temperature followed by rapid quenching in water at room temperature (about 25 °C). According to the results of thermally stimulated depolarization current (TSDC) measurement and XRD patterns, no depletion layer or crystals was found in the rapidly quenched glass samples. The thermally induced nonlinear layer is located in the regions extended from the surface and 8 μm into the bulk. The possible mechanism responsible for the SHG is that the bond deformation of glass structure induced by stress gradient breaks the inversion symmetry of glass. The influencing factors of the SH intensity are also discussed. 相似文献
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Ivan Mukhin Alexandr Voitovich Oleg Palashov Efim Khazanov 《Optics Communications》2009,282(10):1969-4797
A Faraday isolator with one magneto-optical element providing 31 dB isolation ratio for 330 W average power lasers was produced and investigated in an experiment. These remarkable parameters were achieved by increasing the magnetic field and using a [0 0 1] oriented TGG crystal. 相似文献
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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. 相似文献
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Electron paramagnetic resonance (EPR) and thermally stimulated luminescence (TSL) studies were conducted onγ-irradiated CaSO4:UO
2
2+
to elucidate the role of the electron/hole traps in thermally stimulated reactions and to obtain the trap parameters (trap
depth and frequency factor). Intense TSL glow peaks around 140, 375, 400 and 438±2K are observed and their spectral characteristics
have shown that UO
2
2+
and UO
6
6−
act as luminescent centres. EPR studies have shown the peaks at 140 and 400/438K to be associated with the thermal destruction
of O− and SO
4
−
radical ion in two stages respectively. The maximum rate of thermal destruction of SO
4
−
ions (as seen by EPR) in various alkaline earth sulphate matrices investigated in our laboratory is also summarized. The
activation energy which characterizes the electron transfer reaction between SO
4
−
and the dopant ion lies in the range of (0.95±0.15 eV). This value is independent of the dopant and therefore seems to be
characteristic of the binding energy of hole in the SO
4
−
radical ion. 相似文献
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Electron paramagnetic resonance [EPR] and thermally stimulated luminescence [TSL] studies were conducted on self [α]-irradiated239Pu doped calcium chloro phosphate andγ-irradiated239Pu/238UO
2
2+
doped calcium chloro phosphate to elucidate the role of the electron/hole traps in thermally stimulated reactions and to
obtain trap parameters from both TSL and EPR data. TSL glow peaks around 135 K (# peak 1), 190 K (# peak 2), 435 K (# peak
5) and 490 K (# peak 7) were observed and their spectral characteristics have shown that Pu3+ and UO
6
6−
act as luminescent centres in calcium chloro phosphate with respective dopants. EPR studies have shown the formation of the
radical ions H0, PO
4
2−
, O−, O
2
−
and [ClO]2− under different conditions. Whereas the [ClO]2− radical being stable up to 700 K, was not found to have any role in TSL processes, the thermal destruction of other centres
was found to be primarily responsible for the TSL peaks observed. The trap depth values were determined both by using the
TSL data and also the temperature variation of EPR spectra of these centres. 相似文献
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The uncertainty about the existence of quasi-equilibrium (QE) condition during the readout of thermoluminescence and thermally stimulated conductivity glow peaks in real materials causes doubts about the validity of applying the QE-based analytical expressions to analyse these glow peaks. In this paper a simple method is given to verify the QE condition during the readout of these glow peaks in real materials. The method is based on changes in the glow peak shapes caused by changing the heating rate in non-QE cases. It is illustrated by using synthetic glow peaks derived from two different physically meaningful models. 相似文献
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Thermally stimulated luminescence (TSL) studies of gamma-irradiated uraniumdoped K2Ca2(SO4)3 revealed two glow peaks around 400 K and 435 K. Electron paramagnetic resonance (EPR) studies carried out on these samples
have shown the formation of the radical ions SO
4
−
, SO
3
−
, SO
2
−
and O
3
−
. From the study of the thermal stabilities of these radical ions, it was found that the thermal destruction of SO
2
−
and SO
4
−
radical ions are associated with the glow peaks observed around 400 K and 435 K respectively. Uranate ion was identified
as the luminescent centre for the observed TSL glow. The trap depth values for the glow peaks have been determined from TSL
data. 相似文献
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The gravitational instability of an infinitely extending homogenous plasma endowed with several physical mechanisms, namely Hall currents, finite conductivity, ion viscosity and thermal conductivity is considered. The main result is that the various parameters play different physical roles in the perturbed problem. Jeans' criterion is analyzed in the framework of Tsallis' statistics for possible modifications due to the presence of nonextensive effects. A simple generalization of the Jeans' criterion is obtained and the standard values are obtained in the limiting case q=1, q being the nonextensive parameter. 相似文献