Ultrahigh-sensitivity self-mixing laser Doppler velocimetry with laser-diode-pumped microchip LiNdP/sub 4/O/sub 12/ lasers

A self-mixing laser Doppler velocimetry (LDV) has been demonstrated with laser-diode-pumped microcavity LiNdP/sub 4/O/sub 12/ lasers. The feedback signal required for a usable measurement without using photon-correlation techniques was <1 photon per Doppler-beat cycle. An enhancement of LDV signals by resonant excitations of relaxation oscillations has been performed.