Abstract

Single mode diode lasers that operate in the 720-730 nm spectral band of water vapor are required for injection seeding pulsed solid state tunable alexandrite lasers used in remote measurements of atmospheric water vapor. Currently, intracavity etalons are utilized to narrow the spectral bandwidth of alexandrite lasers to about 0.02 cm⁻¹ wide so that the laser output is much narrower than the water vapor absorption linewidth. Injection seeding with a single mode laser will produce pulsed laser band-widths of 0.01 cm⁻¹ or less. The diode seed laser can be frequency locked to water vapor absorption lines by modulating the diode current to dither its frequency and by using the signal from a gas transmission measurement or a photoacoustic cell measurement to generate a feedback signal to the diode current controller. Frequency stabilization of diode lasers to oxygen absorption lines and injection seeding of alexandrite lasers near 768 nm for lidar remote sensing of atmospheric temperature profiles has been demonstrated.¹ Frequency stabilization of 830nm diode lasers to water vapor absorption lines in that region of the spectrum has also been demonstrated.² The salient specifications required of a pulsed laser to measure atmospheric water vapor are listed in Table 1.

© 1991 Optical Society of America