Berlin 2012 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 3: Focus Session: VECSEL

HL 3.5: Topical Talk

Montag, 26. März 2012, 11:45–12:15, ER 164

Quantum-dot VECSEL — •Tim David Germann — Institut für Festkörperphysik EW 5-2, Technische Universität Berlin, Deutschland

Optical pumped vertical external-cavity surface-emitting lasers (VECSEL) based on multiple quantum well active regions have demonstrated multi-watt cw-operation and gaussian beam profiles enabling a bunch of new applications [1]. By introducing quantum-dot (QD) based active regions inside VECSEL new functionalities for such devices are enabled. A broader feasible wavelength range, higher temperature stability, and decreased threshold power densities are demonstrated. In order to achieve sufficient gain for high-power QD-based VECSEL stacking of many QD layers is required. For epitaxial growth processes the challenge is to maintain pseudomorphic growth and constant QD properties throughout the gain section while each QD layer induces a laterally inhomogeneous strain field. Thus QD overgrowth parameters are crucial to recover a smooth growth surface.

Here two conceptually different (In,Ga)As-based approaches for novel VECSEL gain media are demonstrated. Either the Stranski-Krastanow growth mode for QD fabrication or cycled sub-monolayer deposition of InAs embedded into GaAs is used aiming at a spectrally broad gain range or at high modal gain respectively. VECSELs for wavelengths ranging from 950 nm to 1210 nm are fabricated by stacking up to 30 active layers. Up to 1.4 W continuous wave output power and ultra low threshold of only 2.4 kW/cm² are achieved.

[1] A. C. Tropper and S. Hoogland, Extended cavity surface-emitting semiconductor lasers, Progress in Quantum Electronics 30, 1 (2006).