Suppression of the intensity noise in a diode-pumped neodymium:YAG nonplanar ring laser

We investigate the intensity noise properties of a continuous-wave diode pumped Nd:YAG ring-laser system and present results for an active feedback loop that suppresses the relaxation oscillation noise. This system reduces the intensity noise to within 6.1 dB of the quantum noise equivalent level (which is at 1.5/spl times/10/sup -8///spl radic/Hz for 1.5 mA) for frequencies between 10 kHz to 300 kHz and to less than 1/spl times/10/sup -7///spl radic/Hz for frequencies between 300 Hz and 10 kHz. The technical properties of the optimized feedback system are presented. The theoretical limits of performance for the system are discussed and it is shown that the performance is within 3.1 dB of these limits. We also present data from an optical beat experiment demonstrating that the intensity control system does not introduce any new features into the frequency noise spectrum.< >