Suppression of the intensity noise of monolithic non-planar ring oscillator laser

The intensity noise properties of LD-pumped Nd:YAG non-planar ring oscillator (NPRO) laser are experimentally investigated. The increase of the laser output power induces the increase of the frequency of the relaxation oscillation noise (RON) peak from 100 kHz to 280 kHz and the width of the noise spectrum increase. Simultaneously the RON peak value decreases and the phase of π changes across the RON peak. The homemade optoelectronic feedback circuit can provide an adequate gain and a big phase advance of 65° at 500 kHz. Using the circuit, a result better than common results is achieved. For the noise with a RON frequency of 230 kHz, the experiment results show that the RON peak value and low frequency intensity noise are reduced about 45 dB and 20 dB, respectively.