Near-threshold spectral modes and coherence of a semiconductor laser and a diode-pumped neodymium laser

The spectral, coherence, and polarization characteristics of a semiconductor injection laser and a diode-pumped Nd laser operating on second harmonic have been thoroughly traced for the first time during the transition via the generation threshold and on the passage from one mode to another with increasing pump current. It is shown that the behavior of the intensity, coherence, and noise near the threshold is indicative of the possible analogy between laser generation and phase transitions of the first or second order.