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.