We report the demonstration of two-tone optical heterodyne spectroscopy with a tunable lead-salt diode laser. Using high-frequency modulation of the diode-laser injection current, we demonstrated a detection-sensitivity limit of 1 × 10-5 to differential absorption from Doppler-broadened NH3 lines in the 930-cm-1 region. In our experiment, this limit was set by preamplifier noise and the low quantum efficiency of the photodetector. A substantial increase in sensitivity should be possible by using an improved detector, an improved preamplifier, and higher optical power.
© 1986 Optical Society of America
David E. Cooper and J. P. Watjen, "Two-tone optical heterodyne spectroscopy with a tunable lead-salt diode laser," Opt. Lett. 11, 606-608 (1986)