We report the demonstration of near-quantum-noise-limited sensitivity with a lead-salt diode laser using FM spectroscopy and high-speed sweep integration. Using both single-tone and two-tone techniques, we demonstrated an absorption sensitivity of ~2 × 10-7 in a 2.44-Hz bandwidth from a Doppler-broadened NO line at 1856.5 cm-1. The sensitivity in our experiments was limited by laser excess noise, which was about four times the expected quantum-noise level.
© 1988 Optical Society of America
David E. Cooper and Clinton B. Carlisle, "High-sensitivity FM spectroscopy with a lead-salt diode laser," Opt. Lett. 13, 719-721 (1988)