Broadband Intensity Stabilization of a Diode-pumped Monolithic Miniature Nd: YAG Ring Laser

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Abstract
We have built an electronic servo system to reduce the intensity noise in a diode-pumped single-mode monolithic Nd: YAG ring laser with a maximum output power of 350 mW. The servo used two stabilization systems operating simultaneously over two different frequency ranges, each of which detected a fraction of the laser output, amplified and phase shifted the detected signals and used the resultant signals to control the current to the laser diode pump. We achieved a reduction in intensity noise of up to a factor of 30 for frequencies up to about 1 kHz, with some noise reduction observable up to about 30 kHz. At frequencies between around 30 and 200 kHz the intensity noise was increased by a factor of approximately 1·4. In the frequency range 200 to 300 kHz, around the relaxation oscillation frequency of 260 kHz, the intensity noise was suppressed, the reduction factor being approximately 14 at 260 kHz.