Effect of random aperiodicity on threshold gain of a distributed feedback semiconductor laser

摘要

The effect of a small perturbation such as an irregularity in spatial periodicity in the periodic structure of a distributed feedback semiconductor laser is studied. The threshold condition, which takes into account the presence of this perturbation, is derived with the aid of a linearized onehyphen;dimensional solution of the wave equation by the truncated Floquethyphen;Bloch approach. To illustrate the effect of a small random perturbation, variations of mean gain and mean phase parameters, with the coupling parameter tgr; = (kgr;L) and the perturbation parameter rgr;0, are investigated with the aid of approximate expressions obtained by using a truncated MacLaurin series and the firsthyphen;order stationary Gausshyphen;Markov process. For example, it is shown that when the device is operated in the region of moderate coupling, e.g., 0.1(kgr;L)6, the effect of perturbation on the effective gain parameter can be significant. Here, kgr; andLdenote the coupling coefficient and the length of periodic structure, respectively.