Phase modulation to stabilize pump lasers with fiber grating feedback

Summary form only given. It has been observed that under certain laser current, and temperature conditions the optical spectrum of the grating stabilized 980 nm pump laser can become unstable in the time scale of a few seconds to a few minutes. Also, in the same time the monitor current also fluctuates between high and low values. The spectral instability can affect the optical power stability through the narrow-band pump combiner. The monitor current fluctuation can cause the optical power to be unstable under a constant monitor current operation. We proposed a solution to stabilize the optical spectrum and monitor current for semiconductor lasers with fiber grating feedback. By modulating the laser driving current we modulated the laser junction temperature and in turn, we modulated the optical path length of the laser cavity. This averages out the phase fluctuation and provides a stable optical spectrum and a stable monitor current.