Tunable external cavity diode laser that incorporates a polarization half-wave plate

Mid-infrared external-cavity quantum-cascade laser

Single-frequency operation of a 10.4-mum room-temperature multimode quantum-cascade laser was achieved by use of a 17-mm short Littrow-type external-cavity configuration. The spectral intensity of the external-cavity laser was increased as much as 20-fold compared with that of a multimode quantum-cascade laser without an external cavity. A single-frequency tuning range of 76 nm (7 cm(-1)) was achieved. The results were obtained without antireflection coating of the laser output facet.

Improved frequency stability of an external cavity diode laser by eliminating temperature and pressure effects

The construction of a passively stabilized external cavity diode laser operating at 780 nm is reported. The sensitivity of laser frequency to changes in air pressure was studied and subsequently eliminated. The relative frequency stability obtained was 4 × 10(-9) for an integration time of 4000 s.

Long-range tunable diode laser

A novel, simple tuning mechanism for single-mode, pseudo-external-cavity diode lasers has been developed. The model calculations predict that the laser can be tuned continuously by as much as 300 GHz in the vicinity of the chosen frequency without locking it to an external cavity. Experimentally, the continuous tuning range is approximately 120 GHz at constant current and temperature for the 7-cm-long pseudo-external cavity; this is several times more than previously reported. A turning wedge inside the laser cavity is used as the tuning element. The laser is based on a commercial laser diode chip, and a diffraction grating is used for feedback. The total tuning range depends on the laser diode type and can be up to 20 nm.