Driving level dependence of spontaneous emission factor in microcavity DBR surface emitting lasers

Ultra low-threshold surface emitting (SE) lasers are attractive for large scale integration scheme into two-dimensional laser arrays. The control of spontaneous emission using a microcavity is one of the viable methods to realize such ultra low-threshold lasers. We have obtained the enhanced spontaneous emission factor (C factor) in three-dimensional microcavity DBR SE lasers. Recently, several groups have estimated the C factor of the microcavity SE lasers by fitting the calculated threshold curves of output-input characteristics where they assumed that the C factor was constant. However, the C factor must be changing against driving levels. In this study, we would like to show that the variable C factor provides the substantial difference in the L-I characteristic of a microcavity SE laser