Studies on tunable lasers as sources for spectroscopy measurements

Abstract

Spectral tunability of three types of semiconductor lasers is reported. (1) STC LT-50A-03 single spatial mode laser diode. Two diodes were introduced, respectively, in a Littrow extended cavity. Their temperature was modified from 5 degree(s)C to 35 degree(s)C and the injection current was varied between 30 mA and 90 mA. The spectral range covered by each diode was 833.5 nm - 862 nm with laser beam width (Delta) (lambda) equals 2.42 X 10 -4 nm at 50 mW (c.w.); wavelength fluctuations were around 5 X 10 -3 nm for optical cavities thermally unprotected. Less than 10 kHz short term beats were obtained between beams emitted by the extended cavities. (2) HL 7801E Hitachi single longitudinal mode diode laser. Its temperature was varied between 4 degree(s)C and 40 degree(s)C and the injection current was changed, for each temperature, from 45 mA to 90 mA; c.w. laser radiation was tuned between 780.8 nm and 792.5 nm (5 mW output power). (3) Told 9200 Toshiba multimode laser diode (emitting in red, between 600 nm and 700 nm) introduced in an extended Littman cavity, without varying its injection current and/or temperature. A spatial distribution between successively amplified modes was obtained (10 mm at 1.5 m from cavity output). Laser beams wavelengths were measured using a HeNe-I 2 frequency stabilized reference laser emitting at (lambda) equals 632.99095 nm. A comparison between spectral tunability of laser diodes and dye lasers is made, considering both types of lasers as sources for spectroscopy measurements.