Berlin 2012 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 86: Semiconductor Lasers

HL 86.6: Vortrag

Donnerstag, 29. März 2012, 16:30–16:45, EW 015

Interband Cascade Lasers Operating in cw-Mode at Room Temperature — •Robert Weih, Adam Bauer, Alfred Forchel, Sven Höfling, and Martin Kamp — Technische Physik, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany

Within the last years, interband cascade lasers (ICLs) have become the most promising devices to cover the mid-infrared wavelength range between 3 and 4 µ m. They are able to deliver large optical output powers of several hundred milliwatts while consuming less power than quantum cascade lasers (QCLs). Like in traditional diode lasers, amplification of light in ICLs is based on interband transitions. However, the unique band alignments in the GaSb material system - in particular the broken gap of a InAs/GaSb junction - allow a recycling of carriers via a tunnel process. This enables cascaded active regions like in QCLs. The ICLs in this work were grown by molecular beam epitaxy and characterized via temperature dependent electro-optical measurements. In order to lower the threshold current density, design variations concerning the active region and the waveguide structure were made. Changing the composition and thickness of the GaInSb hole quantum well significantly increases the spatial overlap of the wavefunctions involved in the optical transition. This results in a higher recombination probability and hence decreases the threshold current. Furthermore, optical losses could be reduced by increasing the lower cladding thickness from 1.9 µ m to 3.4 µ m. Laser structures incorporating these optimizations were able to operate up to 20^∘C in cw mode. The latest structures showed threshold currents as low as 400A/cm².