GaInAsSb/AlGaAsSb: single-mode DFB lasers for gas sensing in the 2-um wavelength range

摘要

Abstract: Diode lasers emitting in the wavelength range between 1.7 and 4 $mu@m are of particular interest for a large number of applications such as remote gas sensing, molecular spectroscopy and medical applications. Distributed feedback lasers show a singlemode emission and are therefore ideally suited for sensing applications. However the fabrication of DFB lasers usually comprises an overgrowth step of etched gratings, which critically determines the laser properties. We have developed high quality GaInAsSb/AlGaAsSb laser layers and have realized DFB lasers from them without the need to develop overgrowth processes. The laser structures were grown by solid source molecular beam epitaxy on n-GaSb substrates. Depending on the In and the As incorporation in the quantum well the emission wavelength can be varied from 1.5 up to 2.1 $mu@m. Near 2 $mu@m excellent room temperature performance has been obtained for strained Fabry Perot quantum-well lasers. Ridge waveguide lasers were realized by photolithography and reactive-ion etching. Using e-beam lithography and a Cr-metal lift off, DFB gratings were deposited on each side of the ridge. By using an appropriate grating period an emission wavelength around 2 $mu@m was realized. The lasers have clean single mode spectra, threshold currents of less than 40 mA and deliver output powers in excess of 5 mW per facet.!8