Optical Gain Measurements With Variable Stripe Length Technique

Optical gain in semiconductors plays a decisive role when evaluating potential of a given semiconducting material in photonic applications: The occurrence of positive optical gain is a necessary (albeit insufficient) condition for realisation of a semiconductor laser diode. It is therefore highly desirable to have a simple and reliable experimental method enabling us to get information about the presence/absence of gain and, in affirmative case, about its magnitude. Despite the fact that semiconductor lasers are pumped by electric current, the method must be purely optical so as to circumvent possible complications arising from the necessity of fabrication of suitable electric contacts and p-n junctions, detrimental Joule heating etc. In other words, the method should be based on optical rather than electrical pumping.