Study on transition from photonic-crystal laser to random laser
Study on transition from photonic-crystal laser to random laser
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DOI：
10.1364/oe.20.007300
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发表时间：
2012-03-26
期刊：
影响因子：
3.8
通讯作者：
Ueta, Tsuyoshi
中科院分区：
文献类型：
--
作者：
Fujii, Garuda;Matsumoto, Toshiro;Ueta, Tsuyoshi
用有限元方法研究了光子晶体结构中位置无序量对激光阈值的影响，而不是通常采用的时域有限差分方法。考虑了一个二维光子晶体模型，该模型由在一个圆形区域内的三角形晶格上排列的介质柱组成。假设圆柱体是均匀的，无限长。在光子晶体中引入了柱面的位置无序。光学活性介质被引入到圆柱体之间的空隙中。光学活性介质的粒子数反转密度由介电常数的负虚部来模拟。计算了无放大和有放大的电磁场辐射功率之比与频率和介电常数虚部的关系，得到了介电常数虚部的阈值，即粒子数反转密度。这些分析是针对不同程度的紊乱进行的。本文首次用具有可靠精度的数值方法系统地计算了光子晶体激光器到随机激光器的激射阈值的变化。此外，还发现了一个新的现象，即激光阈值随无序度的增加而减小.为了研究圆形系统中激光态的性质，还计算了这些态的电场幅值分布. (C)2012美国光学学会
The dependence of the lasing threshold on the amount of positional disorder in photonic crystal structures is newly studied by means of the finite element method, not of the finite difference time domain method usually used. A two-dimensional model of a photonic crystal consisting of dielectric cylinders arranged on a triangular lattice within a circular region is considered. The cylinders are assumed to be homogeneous and infinitely long. Positional disorder of the cylinders is introduced to the photonic crystals. Optically active medium is introduced to the interspace among the cylinders. The population inversion density of the optically active medium is modeled by the negative imaginary part of dielectric constant. The ratio between radiative power of electromagnetic field without amplification and that with amplification is computed as a function of the frequency and the imaginary part of the dielectric constant, and the threshold of the imaginary part, namely population inversion density for laser action is obtained. These analyses are carried out for various amounts of disorder. The variation of the lasing threshold from photonic-crystal laser to random laser is revealed by systematic computations with numerical method of reliable accuracy for the first time. Moreover, a novel phenomenon, that the lasing threshold have a minimum against the amount of disorder, is found. In order to investigate the properties of the lasing states within the circular system, the distributions of the electric field amplitudes of the states are also calculated. (C) 2012 Optical Society of America