Analysis of the carrier-induced FM response of DFB lasers: theoretical and experimental case studies

A comprehensive analysis of the carrier-induced FM response of DFB lasers is given. Experimentally it is found that the FM response can sometimes vary strongly from chip to chip. In a number of cases anomalies either as a function of frequency or as a function of bias are observed. Theoretically, a dynamic model which includes spectral as well as longitudinal spatial hole burning is presented. The main feature of the model is that local variations of the Bragg wavelength caused by hole burning are rigorously and self-consistently taken into account. By comparing the experimental results with theoretical calculations, it is shown that in DFB lasers, spatial hole burning is an important phenomenon. The model confirms that the dynamic (FM) behavior can vary from DFB chip to DFB chip. The model shows that spatial hole burning is indeed the dominant factor which induces the anomalies that are found experimentally in the FM response