2.1-mu m lasers frequency stabilized against CO2 lines: comparison between fringe-side and frequency-modulation locking methods

A comparison between the use of the fringe-side and the frequency-modulation methods to frequency stabilize diode-pumped Tm-Ho:YAG lasers against linear absorption lines of CO2 near 2.1 mum is reported. Frequency stability was evaluated by monitoring of the beat signal between two independently stabilized Tm-Ho:YAG systems. Frequency instability levels of similar to20 and similar to400 kHz for 1-s integration time were achieved by the frequency-modulation and fringe-side methods, respectively. (C) 2003 Optical Society of America.