IMPROVEMENT OF THE WAVELENGTH TUNABILITY OF ETALON-TYPE LASER-DIODES AND MODE RECOGNITION AND STABILIZATION IN DIODE-LASER SPECTROMETERS

A simple arrangement is presented for the improved wavelength tunabili ty, mode recognition and stabilization of commercial single mode laser diodes. A glass plate with or without a partially reflective coating is mounted in front of the laser diode chip. The plate acts as the low -reflectivity mirror of an extended resonator and helps to select part icular longitudinal modes within the gain profile even where laser act ion is not possible without the feedback. Mode selection is performed by piezoelectric tuning of the external cavity. Mode recognition is ac hieved by the measurement of the reflected intensity from a second ver y thin glass plate in the laser beam acting as a low-finesse etalon. T he intensity pattern from the etalon is used for mode stabilization of the arrangement. (C) 1997 Elsevier Science B.V.