Effect of Pump Area on Lasing Modes in Active Random Media

We investigate the effect of pump area on lasing modes in an active random medium. Considering the structure characteristics in a real experimental system, the random medium is divided into two regions, i.e. pump and non-pump areas. The dependence of lasing modes on the pump area is qualitatively explained by means of the model in which the lasing is ascribed to the interaction of the complex localized modes in the active random medium with local aperiodic quasi-structure with appropriate pump light. There exist different pump sizes for lasing with different modes. As the pump size decreases in this random system, the pump threshold of the lasing modes increases. There are different lasing modes in different excitation regions in this random system. This gives us some information about the dependence of lasing modes on pump areas in active random media.     

活性无序介质中泵浦功率对局域模发射的影响

基于具有局域-非周期-类结构的活性无序介质中的复杂局域模与合适泵浦光的相互作用模型,研究活性无序介质中泵浦功率对局域模发射的影响,定性解释了泵浦功率对局域模发射的影响.结果表明,局域-非周期-类结构的无序介质的透射谱只与介质的结构有关,而与介质的损耗和增益无关,不同的激发模具有不同的泵浦功率阈值.     

The Photon-Number Distribution of the Lasers with Binomial Pump Model

A method on how to take into account pump statistics and spontaneous atomic decays when calculating the photon-number distribution of lasers in photon-number representation is presented. The intracavity phonon-number and extracavity photocount distributions with binomial pump and spontaneous atomic decays are calculated. In two limit cases, the results of calculations transit respectively to the photon-number distributions of systems with common Poissonian pump and regular pump, and both with the spontaneous atomic decays being suppressed.     

Active Control of Cellular Orientation through In-Situ Stress in the Substrate

We investigate the orientation of cells on substrates to find possible methods for controlling the cellular orientation. The force dipole model is employed in our modelling and simulation. The elastic interaction between cells as well as the elastic interaction between the cell and in-situ stress field in the substrate are found to be the two main physical mechanisms to control the cellular orientation. The former interaction dominates the cellular orientation when the in-situ stress is small, while the later dominates when the in-situ stress is large enough. Two cells tend to align perpendicularly on a free substrate, but the cellular orientation varies with the increasing in-situ stress. Two cells tendto align in parallel when the normal stress is large enough. Their direction is perpendicular to the extension stress direction or parallel to the compression stress direction. When the positive in-situ shear stress is large enough, the two cells tend to align at -45°. Based on this theoretical simulation, it is believed that the cellular orientation on substrates can be controlled by thein-situ stresses.     

Theoretical Investigation on the Saturation Effects in Two-photon Pumping Random Lasers

A numerical analysis of the saturation effects of emitted light intensity in two-photon pumping random lasers is presented by adding the saturation item to modify the gain in the diffusive equation. Numerical results show that the emitted intensity reaches its saturation value in a short time interval with sufficient pumping. From the analysis of normalized emitted intensity and saturation intensity, one can obtain a method to control steady output intensity of two-photon pumping random lasing by adjusting some parameters of the random media     

太阳光抽运固体激光工作物质的研究

探讨了适合太阳光抽运的固体激光器工作物质的选择方法,并分析了几种备选工作物质的性质。用Matlab对太阳光谱的现有数据进行了三次样条插值运算,建立了太阳光谱的局部精细离散化模型,并结合红宝石、Nd∶YAG、Yb∶YAG、Nd∶YVO4、Cr∶Nd∶GSGG、掺Nd3 的光学陶瓷和掺Yb3 的石英光纤等激光介质的吸收光谱,进行了太阳光谱与激光介质吸收谱的匹配分析。得出各激光介质所吸收的能量占太阳常量的百分比分别为24.51%,15.98%,2.35%,6.46%,43.91%,15.98%,7.63%。并在一定假设条件下,计算了各介质的阈值抽运功率体密度。综合以上激光介质的材料热特性,选取对太阳光吸收较多,阈值低且热特性好的Nd∶YAG,掺Nd3 光学陶瓷,Cr∶Nd∶GSGG为较适合的太阳光抽运激光工作物质。     

散射颗粒分布对二维随机激光器腔内各模式的影响

采用时域有限差分法数值求解Maxwell方程组,分析了二维随机激光器中光波模式的频谱特性.计算表明,处于不同分布区域的散射颗粒对腔内不同模式的影响有很大差异,处于该模式空间分布区域的散射颗粒比区域外的颗粒对模式有更大的影响.这个特性是随机激光器所独有,并可以用来进行随机激光器的模式选择.     

半导体激光器温控电路分析与测试

阐述了半导体热电致冷器(TEC)的基本工作原理,分析了TEC线性驱动和PWM驱动的原理以及采用PWM驱动的优点,介绍了PID温度补偿控制的原理,并设计了实验.采用相同的测试条件,对MAX1978、ADN8830和线性功率管进行了性能测试,实验数据表明温度控制电路采用PWM驱动功耗更小,全温(-40～60℃)控制效果更好.     

Spatiotemporal Dynamics of Broad-Area Lasers with the Pump Modulation and Injection of External Optical Radiation

Radiophysics and Quantum Electronics - We study the possibility of stabilizing broad-area dynamic class B lasers, which include those with periodic pump modulation, by using injection of external...     

Effect of Pump Bandwidth: Enhancement of Output Intensity Noise Squeezing in Raman Lasers

The effect of the pump bandwidth on the quantum statistical properties of Raman lasers is investigated. It is shown that the pump bandwidth may lead to the enhancement of output intensity noise squeezing even though it reduces the Mandel Q parameter.     

Influence of Spot Size and Spectral Width of the Pump Radiation on the Efficiency of Laser-Diode-Pumped Solid-State Lasers

When mini-solid-state lasers are end-pumped by diode lasers, it is important to have a good overlap between the pump beam and the oscillating mode and to have a pump spectrum that is narrow compared to the width of the absorption peak in the gain medium. We have theoretically studied the influence of the beam radius and the spectral width of the pump on the performance of diode-pumped devices. From the rate equations, the lasing threshold and the circulating intensity is evaluated numerically and the results can be used as a guideline in the design of intracavity doubling lasers. It is also shown that single-mode operation is more difficult when the pump spectrum becomes to wide.     

Taming the pion cloud of the nucleon

We present a light-front determination of the pionic contribution to the nucleon self-energy, Σ(π), to second order in pion-baryon coupling constants that allows the pion-nucleon vertex function to be treated in a model-independent manner constrained by experiment. The pion mass μ dependence of Σ(π) is consistent with chiral perturbation theory results for small values of μ and is also linearly dependent on μ for larger values, in accord with the results of lattice QCD calculations. The derivative of Σ(π) with respect to μ(2) yields the dominant contribution to the pion content, which is consistent with the d[over ˉ]-u[over ˉ] difference observed experimentally in the violation of the Gottfried sum rule.     

Study of Spatial Hole Burning in Distributed Phase-Shifted Distributed Feedback Semiconductor Lasers

In this paper,the Huygens-Fresnel principle is restudied by means of wavelet analysis firstly,this builds the basis of the theory for wavelet optics.Then the theory of wavelet analysis is used to analyze the filtering in spatial domain and spatial frequency domain.For example,it gives the space variable processing for the filtering with wavelet in spatial domain,the match filtering for the filtering with wavelet in spatial frequency domain and a single slit and a round aperture for the wave-front filtering.The feasibility for treating the problems in optical field with wavelet transform is discussed,and the theoretical frame of wavelet optics is built.     

二维随机介质中模式的空间局域化分布

基于随机激光的时域理论,利用时域有限差分法(FDTD)数值求解麦克斯韦方程组和速率方程组,利用分区域计算法,分别计算了整体和局部泵浦二维随机介质时,不同泵浦强度下,不同区域的辐射谱,得出了随机介质中模式的空间局域化分布。计算结果显示,同样条件下不同区域的辐射谱是不同的,且随着激励源泵浦强度的变化,随机激光辐射始终集中在介质中某几个固定区域,但各个区域的随机激射效率不同,在区域之间存在模式的空间范围重叠。利用该方法,可以分析介质的随机分布对随机激射的影响,理论上可以为高激射效率的伪随机介质制备提供一定指导。     

随机介质中电磁波空间分布特性研究

采用随机介质统计模型和FDTD方法模拟了随机介质电场空间分布根据光子局域化理论,讨论了电场的空间分布和介电常数涨落的关系,结果表明,在一定的介质密度下,电磁场是局域化的,其空间分布和介质介电常数的涨落密切相关.     

基于曲面空间合束的多单管半导体激光光纤耦合

随着单管半导体激光器光纤耦合技术的不断发展,为了进一步提高多单管半导体激光器的输出功率,本文采用曲面空间排列方式对多个单管半导体激光器进行合束研究,使更多数量的单管半导体激光器耦合进入同一光纤中,获得更高的输出功率。文中利用ZEMAX光学设计软件进行仿真模拟,将34只波长为975 nm、输出功率为10 W的单管半导体激光器合束聚焦后耦合进芯径200 μm、数值孔径0.22的光纤中,获得耦合效率91.76%、输出功率312.03 W的激光系统。实验中,将17只单管半导体激光器耦合进芯径200 μm、数值孔径0.22的光纤中,在10.5 A的驱动电流下,输出功率为100.5 W,系统耦合效率为68.46%。     

Optimization of Passively Q-switched Lasers by Taking into Account Intracavity Laser Spatial Distribution

The intracavity photon density and the initial population-inversion density in the diode-pumped passively Q-switched lasers are assumed to be Gaussian spatial distributions. The space-dependent rate equations are solved numerically. The key parameters of an optimally coupled passively Q-switched laser under Gaussian approximation are determined, and a group of general curves are generated for the first time. These key parameters include the optimal normalized coupling parameter and the optimal normalized saturable absorber parameter that maximize the output energy, and the corresponding normalized energy, normalized peak power, and normalized pulse width. The curves clearly show the dependence of the optimal key parameters on the parameters of the gain medium, the saturable absorber, and the resonator. In addition, the importance including the space variation is also shown. The optimal calculations for a diode-pumped passively Nd: YVO₄ laser are presented to demonstrate the use of the curves and the related formulas.     

激光相干控制选态激发的理论研究

系统地研究了三色相位干的激光场与三能级体系的相互作用过程，证明了态的布居几率依赖于光场的相的相位和振幅属性，从理论上指出用于相干光场实现选态激发的可能性，并首次提出用相干光场去实现泛频激发的可行性和优点。