Under adequate conditions it reduces the laser linewidth, but it also leads to unstable emission and, for large feedback, to the collapse of the laser coherence. Despite the importance of this phenomenon in many applications and many current studies, the physical mechanisms underlying the phenomenon are controversial.
Upper figure are experimental observations.
Potential uses are wavelength conversion, ultrafast codification and all-optical clock signal extraction. However, there was no useful modeling of these devices available accounting for wavelength dependence of gain and refraction index. Using our previous mesoscopic modeling of the optical susceptibility of active semiconductor media which takes into account the wavelength dependence of the response we have studied the characteristics of the output beam of a tapered SOA for high power applications. Our modeling predicts, in agreement with experimental observations, that in a SOA with larger optical confinement, the advantage of requiring a smaller injection current, for a fixed amplifying factor, is compensated by a larger tendency to filamentation of the output beam, as well as for a smaller saturating power of the device. A. Gahl and S. Balle, IEEE Photon.