Investigation of multi-longitudinal mode instabilities in semiconductor lasers using a coupled mode model with gain dispersion

Summary form only given. Semiconductor lasers used as transmitters in D-WDM are required to have a fixed frequency over a wide range of operating conditions. Dynamic instabilities can cause the laser to spontaneously hop to a different cavity or Bragg mode. Predicting where longitudinal instabilities occur is useful for designing stable sources for optical communication. The author presents a simple coupled mode model which explicitly includes the gain dispersion dynamics. This model is rigorously derived from a full partial differential equation which included the gain dispersion as an additional spatial derivative. When the gain dispersion is missing the laser lases in the lowest order mode even if this mode is not the mode closest to the gain peak. This curious artifact of the truncation order arises from a natural instability in semiconductor material where power is dynamically transferred from higher energy modes to lower energy modes. Without gain dispersion this energy transfer continues until the lowest order mode in the model is reached. With gain dispersion this energy transfer is arrested and the final lasing mode is that which is closest to peak gain.