Determination of Cavity Loss in Proton Implanted Vertical-Cavity Surface-Emitting Lasers

The cavity loss and the threshold gain of the proton implanted 780-nm vertical-cavity surface-emitting laser(VCSEL)s are determined by varying the mirror loss with optical feedback. Taking the nonlinear gain effect into account, the total internal loss of αt = 68 cm-1 and the threshold modal gain of gth = 89 cm-1 are obtained in a gain guided VCSEL whose diameter is 15 µm. This method can handle the cases of large optical feedback or large threshold gain where the nonlinear gain effect becomes significant. Unlike the other methods, our approach works well for gain-guided lasers where thermal effect generates unreliable values of differential quantum efficiency.