给出了一种适用于空间应用的全固态高重复频率窄脉冲激光器。激光器采用超稳双porro棱镜直线谐振腔, 以LD侧面抽运Nd∶YAG板条, 磷酸氧钛铷(RTP)晶体作为电光调Q开关, 并利用偏振耦合输出激光。实现了激光脉冲重复频率为1 kHz、平均功率为1.15 W、脉冲宽度为1.3 ns、光束质量因子M2为M2x=1.20和M2y=1.23、波长为1064 nm的脉冲激光输出。激光器结构紧凑, 性能良好, 可作为未来新型空间探测激光雷达系统的光源。

Gain medium of modern high-average-power solid-state lasers can produce distortion for the reason of thermal effect, such as YAG. Wavefront distortion and depolarization often occur simutaneously. The thermal stress of the high-power solid state laser slab is becoming a serious problem for hindering the further power increasing of the laser. A method for calculating the thermally induced refraction index in a pumped heat capacity slab laser was studied. In this method, the fourth-rank piezo-optics tensors of YAG crystal were transformed from the crystal lattice coordinate system to the laboratory coordinate system. With these new tensors, the thermally induced stress birefringence in a solid-state laser can be analyzed easily for any stress distribution. Furthermore, the calculations show that the birefringence in a zigzag slab depends on the angle under which the slab is cut from the boule. A theoretical description of the thermal and stress characteristics of heat capacity slab laser in two dimensional was also presented.

We investigate intersubband Rabi flopping in modulation-doped semiconductor quantum wells with and without the propagation effects, respectively. It is shown that propagation effects have a larger impact on Rabi flopping than the nonlinearities rooted from electron-electron interactions in multiple quantum wells. By using ultrashort \pi pulses, an almost complete population inversion exists if the propagation effects are not considered; while no complete population inversion occurs in the presence of propagation effects. Furthermore, the magnitude of the impact of propagation effects may be controlled by varying the carrier density.

高平均功率固体激光器的增益介质由于受热而容易发生畸变,如常用材料YAG,波前畸变和去偏振现象会同时发生,高热负载固体激光介质的热效应已成为制约激光器输出功率进一步提高的严重障碍。给出一种计算热容型板条激光器热感生折射率的方法。把YAG晶体的四阶压光张量从晶胞坐标系转换到实验室坐标系,采用经过坐标转换后的新的张量,可以分析在YAG激光器中任意应力分布引起的热感应双折射。进一步的计算表明,在zigzag板条激光器中,应力双折射率与板条从晶体毛胚上切割成材的角度有关。同时也对热容板条激光器的热效应和应力特性进行了二维的理论性概述。

The solid state heat capacity laser (SSHCL), as one of the most important high-power solid-state lasers, has attracted extensive attention. Numerical simulation of temperature and stress distributions of laser crystal slab in the heat capacity operation mode is a major means to understand the specific property of the laser. Using the method of plane stress approximation, the two-dimensional (2D) mathematical formulas that describe the temperature and stress distributions of laser diode (LD) pumped heat capacity slab laser are derived. Then the absorbed pump power density, 2D distributions of temperature and index of refraction are also analyzed and discussed. According to the results, the 2D distributions of temperature and stress are more homogeneous than that of the one-dimensional distributions.

Based on the laser rate equations in a typical four-level system, we research the temperature-dependent gain characteristics of a solid-state heat-capacity laser (SSHCL) involving the small-signal gain coefficient and the gain distribution's uniformity. The influences of doping concentration of active ions and initial operating temperature on the small-signal gain coefficient are discussed for Nd-doped glass heat-capacity laser. Furthermore, the gain distributions of a slab laser gain medium operating in SSHCL mode are discussed.

In the 9th laser system of Shenguang II inertial confinement fusion (ICF) facility, tunable Fabry-Perot (F-P) filter is applied to compensate the FM-AM effect. According to the technical requirements of compensation device, a precise displacement monitor system using the capacitive displacement sensor with nanometer scale precision to stabilize the spacing of the tunable F-P filter is proposed firstly, then the basic structure and operating principle of the monitor system are analyzed. The scheme design of the driving circuit of capacitive displacement sensor, the data processing as well as the system controlling program are discussed in detail, and the precision of capacitive displacement sensor is calibrated. The experimental results show that the spacing stability of the tunable F-P filter is better than 15 nm/h and the modulation depth of the FM-AM effect is better than 4% by introducing the displacement monitor system.

固体热容激光器(SSHCL)作为高功率固体激光器的一个重要发展方向, 引起人们广泛关注。数值模拟激光介质板条在热容方式下工作的温度和应力分布是了解该类激光器工作特性的一种有效手段,采用平面应力近似法导出了半导体激光器抽运热容激光介质板的二维温度和应力分布公式,同时也对二维抽运光吸收密度、介质板温度分布和折射率变化进行了分析与讨论。数值计算的结果表明二维效应的温度分布和应力分布要比一维效应给出的分布更均匀。

As the best candidate for the high power lasers in next generation, the solid state heat capacity laser (SSHCL) has attracted extensive attention. The principles, power scaling of SSHCL, distributions of fluorescence, temperature in a pumped slab cooling, and slab are presented. The effects of temperature in medium slab on the output power of laser are discussed in detail. Several key points about design are also described.

Based on the fundamental theory of heat transfer, the mathematical formulas that describing the transient temperature distributions of two-sided laser diode (LD) pumped Nd∶GGG (gadolinium gallium garnet) heat capacity slab laser were derived in this paper. By means of finite element analysis by ANSYS, transient temperature fields and stress distribution in the slab medium were simulated with various boundary conditions, while the beam distortions induced by thermal gradients were analyzed briefly. The obtained results could benefit to the primary designing of solid state heat capacity laser (SSHCL). Numerical analysis proved that under incomplete adiabatic boundary conditions, it would result in temperature gradients perpendicular to the optical axis. About 0.2 μm optical path differences would occur between the edge and optical axis of the slab. In addition, the thermal distributions in the slab during the subsequent cooling stage were mainly studied. The influences of different cooling methods such as air cooling, water cooling and mist cooling were discussed and cooling methods suitable for a SSHCL were briefly studied.