Low-intensity-noise operation of Nd : YVO4 microchip lasers by pump-noise suppression

We report on near-quantum-limited intensity noise of Nd:WO, microchip laser s pumped with pump-noise-suppressed diode lasers. The low-frequency intensi ty noise of the microchip lasers is found to depend on mode correlation eff ects in the absorbed radiation from the diode laser pump source. A minimum intensity noise of 0.5 dB above the standard quantum-noise limit at a frequ ency of 250 kHz is obtained by pumping with a grating-feedback diode laser. An accurate description of the measured intensity-noise spectra by a quant um-mechanical Langevin rate-equation model is achieved by consideration of the nonlinear gain saturation that is due to the finite lifetime of the low er laser level. (C) 1999 Optical Society of America [S0740-3224(99)00502-0] .