An overview of tunable diode laser technology development

The development of tunable diode lasers is studied. The lead-salt diode lasers are useful for spectroscopic studies in the 2-30 micron range and for long distance fiber-optical communications. Improvements in diode laser performance related to long-term reliability, the purification of mode properties, and higher operating temperatures are discussed. The fabrication of homojunction diffused lasers from Pb(1-x)Sn(x)Te and PbS(1-x)Se(x) single crystals by diffusion techniques is examined. Lead-telluride diode lasers which operate to 115 K CW and are fabricated by mesa stripe geometry diodes with 20-35 micron stripe widths are considered. The use of europium and ytterbium in lattice-matched, double-heterojunction, lead-chalcogenide diode lasers lead to CW operating temperatures of up to 147 K; these structures for the lasers were grown lattice-matched to 100 line oriented PbTe substrates by molecular beam epitaxy. The relation between the threshold current of quantum well lasers and temperature is investigated. A technique for the fabrication of lead-salt, cleaved-coupled-cavity diode lasers which improve single-mode operations, is described.