Nitric oxide is detected by a new technique in which tunable infrared radiation from a spin-flip Raman laser is used to measure the absorption spectrumn of a gas sample by optoacoustic spectroscopy. This technique is sensitive enough to detect a concentration of 0.01 part per million of nitric oxide pollution in air samples.

http://science.sciencemag.org/content/sci/173/3991/45.full.pdf

Nitric oxide air pollution detection by optoacoustic spectroscopy

High intensity Raman interactions

A cw difference-frequency spectrometer has been developed for the 2.2 to 4.2 μm infrared region by mixing argon and tunable dye lasers in LiNbO3. A resolution of 5 × 10−4 cm−1 with continuous scans up to 1 cm−1 and a scan precision better than 2 × 10−3 cm−1 have been achieved. Tunable ir powers of ~1 μW have been obtained, enabling sensitive absorption measurements and real-time spectroscopy. The range, resolution, speed, and sensitivity of this difference-frequency technique are demonstrated by absorption traces of water vapor, ammonia, methane, and nitrous oxide.

Doppler-limited molecular spectroscopy by difference-frequency mixing*

This is a tutorial review on the subject of mode selection in lasers. We begin with a historical review. After an introduction to the subject of modes in laser resonators and a brief review of the theory of laser gain saturation, the main body of the paper is devoted to a discussion of various mode-selection techniques, many which can be used to produce single-frequency laser operation. We discuss some systems for frequency stabilization of single-frequency lasers, and conclude with examples of laser applications where mode-selection techniques are required.

Mode selection in lasers

The first cw operation of a Raman laser is reported. Using a 5‐μm CO laser we have observed two stimulated Stokes lines by scattering from spin‐flip excitations of conduction electrons in InSb in a magnetic field. Observed threshold powers were about 200 mW for the first Stokes line.

E. D. Shaw

Papers

Tunable Spin-Flip Laser and Infrared Spectroscopy