Project Title:

A Tunable, Infrared Source for Molecular Spectroscopy Using Room-Temperature Diode

08.08-9500
911897
A Tunable, Infrared Source for Molecular Spectroscopy Using Room-Temperature Diode
Lasers
Aerodyne Research, Inc.
45 Manning Road
Billerica
MA
01821
Roger S.
Putnam
508-663-9500
JPL
NAS7-1171
147

08.08-9500
911897

Abstract:

A Tunable, Infrared Source for Molecular Spectroscopy Using Room-Temperature Diode
Lasers
Laser sources currently available for molecular spectroscopy in the 2 to 30 micron
region are lead-salt diode lasers cooled to liquid-helium temperatures. They typically
produce ten modal frequencies at once. These problems require a monochromator just
to clean up erratic tuning behavior of the laser source and a $60,000 system for
closed circuit cooling, electrical control, and optics. Despite these problems, the
importance of these wavelengths in detecting trace species as diverse as greenhouse
gases such as methane from swamps to nitrous oxide from combustion processes has
forced many researchers to use these unwieldy laser sources. The opportunity here
is to apply inexpensive, tunable, room-temperature diode lasers; these are now readily
available with enough power to directly drive a nonlinear difference-frequency infrared
generator when previously $35,000 dye lasers were required. The fact that the new
diode lasers produce enough power, are available with 10 MHz linewidths without an
external cavity, are tunable, and are remarkably efficient make this application
an immediate opportunity. The objectives involve the basic demonstration of generating
tunable infrared radiation in the 2.5 micron region using a diode laser and a KTP
crystal, and the measurement of the resulting optical linewidth. The anticipated
results from Phase I include a rudimentary demonstration of gas-phase nitrous-oxide
or hydrofluoric-acid detection.
An inexpensive tunable source of narrowband infrared will permit the construction
of air monitoring equipment for a wide variety of pollutants. The market for this
instrument already exists in this period of increased social awareness and government
regulations.
infrared laser, nonlinear optical, molecular spectroscopy, difference frequency