COIL基于小信号增益系数的最佳流量配比选择

氧碘化学激光器（COIL）的混合喷管内发生的是气体动力学、化学反应动力学以及光学等相互耦合的复杂过程，每个过程都对COIL性能有着至关重要的影响。利用3维CFD技术，通过求解层流Navier—Stokes方程与组分输运方程，结合10种组分和21个基元反应的化学反应模型，对简化后的化学氧碘激光RADICI。模型在亚声速段横向射流情况下，不同的主副流流量配比对小信号增益系数的影响情况进行了比较与分析。结果证明：过高或过低的碘分子浓度均不利于产生合理的小信号增益系数；存在最佳流量配比使小信号增益系数得到显著提高且分布均匀。

无缓冲气COIL扩压器流场数值模拟

以无缓冲气化学氧碘激光器（COIL）实验器件的数据计算得到的混合喷管出口参数平均值作为光腔入口条件，对6种不同构型的扩压器从光腔入口至扩压器出口的流场进行了数值模拟，得出了各流场参数分布；对不同构型扩压器的流场特点、总压恢复性能进行了分析；研究了扩压器出口背压对流场参数的影响。结果表明：对于主流无缓冲气的COIL，等截面扩压器具有较好的压力恢复性能；增大扩压器出口背压可以使扩压器的压力恢复性能提高，然而，较高的背压使激波串向光腔方向移动，从而使光腔流场受到干扰，影响光腔的光束质量。

亚声速段横向射流对Coil性能影响的数值研究

在化学氧碘激光的混合喷管内发生的是一个气体动力学、化学反应动力学以及光学等相互耦合的复杂过程,每个过程都对COIL性能有着至关重要的影响.利用三维CFD技术,通过求解层流Navier-Stokes方程与组分输运方程,对简化后的化学氧碘激光RADICL模型进行数值模拟与分析,对COIL的气动和增益特性进行探讨.在不同的射流穿透条件下,计算COIL混合喷管中的混合与化学反应过程,发现穿透深度决定了增益的分布特性以及过度穿透条件下的非定常结构,

Single curved fiber sedimentation under gravity

Dynamics of single curved fiber sedimentation under gravity are simulated by using the lattice Boltzmann method. The results of migration and rotation of the curved fiber at different Reynolds numbers are reported. The results show that the rotation and migration processes are sensitive to the curvature of the fiber. (c) 2007 Elsevier Ltd. All rights reserved.

流量配比对Coil增益分布影响的数值研究

利用三维CFD技术,通过求解层流Navier-stokes方程与组分输运方程,对简化后的化学氧碘激光RADICL模型进行数值模拟与分析,结合10种组分和21个基元反应的化学反应模型,对COIL亚声速段横向射流情况下,不同的主副流流量配比对化学氧碘激光器性能的影响进行分析与比较.结果证明,过高或过低的碘分子浓度状态均不利于合理、可观的小信号增益系数产生.存在一个最佳流量配比范围,与之对应的工作状态下,COIL的小信号增益系数会得到显著提高.

Enhanced dispersive wave generation by using chirped pulses in a microstructured fiber

A theoretical investigation on the nonlinear pulse propagation and dispersive wave generation in the anomalous dispersion region of a microstructured fiber is presented. By simulating the dispersive wave generation under different conditions. it is found that the generation mechanism of the dispersive wave is mainly due to the pulse trapping across the zero-dispersion wavelength. By varying the initial pulse chirp, the output spectrum can be broadened and the intensity of the dispersive wave can be obviously enhanced. In particular, there exists an optimal positive chirp which maximizes the intensity of the dispersive wave. This effect can be explained by the energy transfer from the Raman soliton to the dispersive wave due to the effect of the pulse trapping and the effect of the higher-order dispersion. From the phase aspect, the explanation of this effect is also included. (C) 2004 Elsevier B.V. All rights reserved.

Active phase control and frequency chirp effects on supercontinuum generation in high birefringence photonic crystal fiber

An acoustic-optics programmable dispersive filter (AOPDF) was first employed to actively control the linearly polarized femtosecond pump pulse frequency chirp for supercontinuum (SC) generation in a high birefringence photonic crystal fiber (PCF). By accurately controlling the second order phase distortion and polarization direction of incident pulses, the output SC spectrum can be tuned to various spectral energy distributions and bandwidths. The pump pulse energy and bandwidth are preserved in our experiment. It is found that SC with broader bandwidth can be generated with positive chirped pump pulses except when the chirp value is larger than the optimal value, and the same optimal value exists for the pump pulses polarized along the two principal axes. With optimal positive chirp, more than 78% of the pump energy can be transferred to below 750 nm. Otherwise, negative chirp will weaken the blue-shift broadening and the SC bandwidth. (C) 2007 Elsevier B.V. All rights reserved.

Generation of sub-5 fs pulses through cascade of filamentation and hollow fiber compression

A pulse-compression scheme based on cascade of filamentation and hollow fiber has been demonstrated, Pulses with duration of sub-5 fs and energy of 0.2 mJ near 800 nm have been generated by compressing the similar to 40 fs pulses from a commercial laser system. This method is promising to generate near monocycle high energy pulses. [GRAPHICS] Measured autocorrelation curve of the final compressed pulses with duration of sub-5 fs (black solid) and the simulated autocorrelation curve of 4.6 fs pulse near 800 rim (red dash) (C) 2008 by Astro Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA