Berlin 2005 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 32: Halbleiterlaser I
HL 32.2: Vortrag
Samstag, 5. März 2005, 15:15–15:30, TU P-N202
Tuning of the emission wavelength in mid-infrared quantum-cascade micro-lasers by controlling the cavity length — •S. Höfling1, P. Eugster1, J. Seufert2, J. Koeth2, J.P. Reithmaier1, and A. Forchel1 — 1Technische Physik, Universität Würzburg, Würzburg — 2nanoplus, Nanosystems and Technology GmbH, Gerbrunn
The fabrication and investigation of edge-emitting quantum-cascade (QC) lasers and micro-lasers with monolithically integrated deeply etched semiconductor-air Bragg-mirrors based on GaAs is reported. We observe a reduction of the threshold current density by 25 % and an increase of the operation temperature by 23 K to 315 K for 800 µm by employing Bragg-mirrors. Devices with ultra-short cavities of about 100 µm (36 times the wavelength) operate up to 260 K. At 80 K, these devices show threshold currents as low as 0.63 A and output levels up to 56 mW. In these devices, longitudinal single mode operation with output levels exceeding 7.7, 5.6 and 2.8 mW was measured at 180, 200 and 240 K, respectively. This can be attributed to the limited gain bandwidth of QC lasers and the large mode spacing in these devices, which is proportional to the square of the wavelength. We demonstrate that tuning of the emission wavelength is feasible by controlling the cavity length and thereby selecting the spectral position of the Fabry-Perot modes. The tuning range of the low excitation modes of devices, whose cavity lengths vary in steps of 1 µm (from 98 to 105 µm), is about 180 nm, centered at 9.18 µm.