A theoretical model used to analyze the output characteristics of fiber grating external cavity semiconductor lasers

Using the ray trace method, the expression of the output spectrum of the fiber grating external cavity semiconductor laser (FGESL) has been deduced and the fine structure of the output spectrum has been investigated. Due to the fiber grating (FG) external cavity, within the reflection bandwidth of the FG, the energy distribution varies seriously, there exist many peaks and the number of peaks is related to the length of the external cavity. With increase in the bias current, the output power and side-mode suppression ratio (SMSR) of FGSEL tend to increase accompanied by fluctuation, and the fluctuation will weaken with the decrease in the reflectivity of the front facet of the semiconductor laser.