Lasing modes in a spiral-shaped dielectric microcavity.

The resonance patterns and lasing modes in a spiral-shaped dielectric microcavity are investigated through passive and active medium calculations. We find that the high-Q resonance modes are whispering-gallery-like modes, and these resonance modes can be easily excited as lasing modes. We also find that the quasi-scarred resonance mode, which shows strong directional emission beams from the cavity boundary, can be excited with selectively applied external pumping.

Observation and investigation of off-axis modes in a high-power Nd:YAG laser.

Unusual transverse patterns were observed in a cw-lamp-pumped Nd:YAG laser near the boundaries of the stability zones of the laser resonator. An interpretation of these patterns is given in terms of off-axis modes, which can be excited owing to spherical aberrations and astigmatism of the thermal lens and thermally induced birefringence. Additional evidence of the off-axis character of the observed modes was obtained by analysis of the temporal behavior of the observed patterns.