Suppression of the low frequency intensity noise of a single-frequency Yb³⁺-doped phosphate fiber laser at 1083 nm

The suppression of the low frequency intensity noise of a 1083 nm single-frequency Yb³⁺-doped phosphate fiber laser is reported. The noise suppression scheme is to use a liquid crystal device as a variable attenuator to modulate the laser power to close to the desired level. The achieved long term (12 h) laser instability is less than 0.2%, while the relative intensity noise (RIN) has been decreased to lower than −140 dB Hz⁻¹ at frequencies from 250 Hz to 1 kHz. Moreover, the laser linewidth value remains the same as before suppression, while the degree of polarization (DOP) declined slightly. (paper)