Harmonics-Assisted 50-Fold Optical Phase Amplification with a Self-Mixing Thin-Slice Nd:GdVO4 Laser with Wide-Aperture Laser-Diode Pumping

Harmonic-assisted phase amplification was investigated in a 300-mm-thick Nd:GdVO4 laser with coated end mirrors in the self-mixing interference scheme. The key event is the self-induced hybrid skew cosh Gaussian-type transverse mode oscillation in a thin-slice solid-state laser with wide-aperture laser-diode pumping. The present hybrid skew-chG mode was proved to be formed by the locking of nearly frequency-degenerate TEM00 and annular fields. The resultant modal-interference-induced gain modulation at the beat frequency between the two modal fields, which is far above the relaxation oscillation frequency, increased experimental self-mixing modulation bandwidth accordingly. Fifty-fold phase amplification was achieved in a strong optical feedback regime.