Arif M, Karim M A
Electro-Optics Program, University of Dayton, Dayton, Ohio 45469-0245, USA.
Appl Opt. 2000 Feb 20;39(6):954-61. doi: 10.1364/ao.39.000954.
A novel power-series method to solve the coupled-wave equations is introduced. The method is used to calculate the threshold gain margins of a complex-coupled distributed-feedback laser as functions of the ratio of gain coupling to index coupling (|kappa(g)|/|kappa(n)|) and of the phase difference between the index and the gain gratings. For coupling coefficient |kappa|l < ., the laser shows a mode degeneracy at specific values of the ratio |kappa(g)|/|kappa(n)| for cleaved facets. At phase differences pi/2 and 3pi/2 between the gain and the index gratings, an antireflection-coated complex-coupled laser becomes multimode, and a different mode starts to lase. The effect of facet reflectivity (both magnitude and phase) on the gain margin of a complex-coupled DFB laser is also investigated. Although the gain margin varies slowly with the magnitude of the facet's reflectivity, it shows large variations as a function of the phase. Spatial hole burning was found to be minimum at phase difference npi, n =, ..., and maximum at phase differences pi/2 and 3pi/2.
介绍了一种求解耦合波方程的新型幂级数方法。该方法用于计算复杂耦合分布反馈激光器的阈值增益裕度，作为增益耦合与折射率耦合之比（|κ(g)|/|κ(n)|）以及折射率光栅与增益光栅之间相位差的函数。对于耦合系数|κ|l <...，对于解理面，激光器在特定的|κ(g)|/|κ(n)|比值下表现出模式简并。在增益光栅与折射率光栅之间的相位差为π/2和3π/2时，镀有增透膜的复杂耦合激光器会变成多模，并且会有不同的模式开始激射。还研究了端面反射率（幅度和相位）对复杂耦合DFB激光器增益裕度的影响。尽管增益裕度随端面反射率的幅度变化缓慢，但它随相位变化很大。发现空间烧孔在相位差nπ（n = 0,1,2,...）时最小，在相位差π/2和3π/2时最大。
