Analysis of fiber-grating-coupled semiconductor lasers for WDM applications

A novel external-cavity geometry for a semiconductor laser can be constructed by coupling the laser light through an antireflection coating on the laser diode face into a fiber, some distance along which a Bragg grating is written in the fiber core. The grating forms one mirror defining the cavity, a high reflectivity coating on the back end of the diode serving as the other mirror. After reviewing the work in this area, we will turn to cw operation, where in certain circumstances the stability against mode hopping has been observed to depend on the chirp of the Bragg grating. A simple physical picture of such behavior is possible because the cavity round trip time is much greater than the transit time of the light in the gain medium. This picture will be outlined, and used to explore the range of behavior possible when the laser is directly modulated. Recent theoretical and experimental studies focusing on applications for wavelength-division multiplexing will be discussed