Berlin 2008 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 34: Semiconductor Laser
HL 34.9: Vortrag
Mittwoch, 27. Februar 2008, 16:30–16:45, EW 202
Wavelength stabilized high-brightness tapered quantum dot lasers — •Christian Zimmermann1, Pia Weinmann1, Wolfgang Kaiser1, Johann-Peter Reithmaier2, Martin Kamp1, and Alfred Forchel1 — 1Technische Physik, Universität Würzburg, Am Hubland, D-97074 Würzburg — 2INA, Universtität Kassel, Heinrich-Plett-Str. 40, D-34132 Kassel
In high-brightness semiconductor lasers, the use of quantum dots (QD) as active material has a number of advantages over the use of quantum wells (QW), e.g. lower threshold densities, reduced carrier diffusion and filamentation. Another beneficial property of QD lasers is their reduced temperature dependence of the emission wavelength. The decrease of the bandgap with increasing temperature is partially counterbalanced by a shift of the gain maximum caused by the increasing losses. This reduces the change of the emission wavelength Δ λ / Δ T by a factor of two compared to quantum well devices.
We have investigated the performance of quantum dot based tapered lasers emitting at 920 nm. The devices have output power of more than 3W with a good beam quality. The extra losses of the taper have an impact on the operation point of the laser on the gain curve, leading to a dependence of Δ λ / Δ T on the taper angle. A minimum value of 0.16 nm/K was measured for lasers with a 1o taper. In addition, this effect was used to determine the taper losses for various taper angles. A further stabilization of the emission wavelength can be achieved by the incorporation of distributed Bragg reflectors (DBRs). These devices emit on a single wavelength with more than 1W output power.