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Construction of an Extended Cavity Tunable Diode Laser.
Petr Liska, Bridgewater State College,
Harold Metcalf and John Noé, Laser Teaching Center, University
at Stony Brook.
A diverse and vast amount of experiments at the forefront of
experimental physics typically use diode lasers as an integral part of
their arrangement. However, researchers who use unmodified commercially
available diode lasers run into several complications. The laser diode
that is purchased is often not of the same wavelength as is advertised;
thus the researcher's desired wavelength is not met. Because the
semiconductor has such a short external cavity, it is very sensitive to
the injection current, changes in room temperature, and has a large
linewidth making it harder to tune.
To obtain a finely tuned diode laser, temperature and current controlling
of the diode laser are used in conjunction with an extended semiconductor
cavity. The wavelength may vary by approximately 2.5 nanometers every 10
degrees Celsius. This is achieved by mounting the hermetically sealed
assembly atop a thermoelectric cooler, which uses the Peltier effect.
Furthermore, the variation of the injection current may be used as an
additional control for the wavelength output of the diode. The power range
of 70 mW as controlled by the injection current adjusts the wavelength by
a span of only 4 nanometers.
The extended cavity consists of a diffraction grating adhered to a mirror
mount and is used for grating feedback. That in turn is used to reduce the
linewidth sufficiently enough in order to provide much better tunability.
In the next three weeks, the tunable diode laser will be specifically
applied to research in the areas of Second Harmonic Generation in a PPLN
Crystal and Saturated Rubidium Spectroscopy.
This study was supported in part by NSF grant PHY99-12312.
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