Thresholds of lasing modes localized on MUPO and UPO in fully chaotic microcavity lasers

Abstract

We experimentally observe the lasing of a single-mode group in a rounded D-shape InGaAsP semiconductor microcavity laser when the cavity is fully chaotic. Although there are numerous unstable periodic orbits and marginally unstable periodic orbits, the lasing mode group is localized on a pentagonal period-5 unstable periodic orbit and marginally unstable periodic orbits for each rounded D-shape microcavity laser with parameters r=0.85R, φ= 5° and r=0.5R, φ=80°, respectively, near above the lowest threshold for CW current injection. By means of numerical analyses with ray and wave dynamics, we have theoretically predicted the dominant lasing of the pentagonal mode group by considering the linear gain condition at the lowest threshold condition. We calculate the threshold parameters depending on the effective pumping region for each periodic orbit, and have obtained that the resonance modes localized on the pentagonal periodic orbits have the lowest threshold parameter for our experimental condition, which has a 3μm inward gap between the current contact region and the side-wall of the microcavity. Consequently, we have confirmed that the path length and unidirectional emission from the experimental the result well coincide with our theoretical prediction.