Demonstration of low-frequency intensity noise reduction for fiber sensors powered by diode-pumped Nd-YAG lasers

Diode-pumped Nd-YAG lasers are being used in fiber sensors for their frequency stability which alleviates the requirements on interferometer path balancing associated with semiconductor lasers. Unfortunately, low-frequency intensity fluctuations induced by the broad-area laser pump, as well as noise associated with launching light into a single-mode fiber, can limit the sensor's minimum detectability. The authors measured the low-frequency relative intensity noise (RIN) of these lasers, implemented feedback into an external modulator to compensate for both laser and launching noise, and reduced the RIN to -100 dB/ square root Hz at 1 Hz.<
>