Regensburg 2004 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 15: Photonische Kristalle III

HL 15.5: Vortrag

Dienstag, 9. März 2004, 11:15–11:30, H17

Low loss GaAs based photonic crystal waveguides — •Helmut Scherer¹, Martin Kamp¹, Stefan Deubert¹, Hans-Peter Reithmaier¹, Alfred Forchel¹ und Reinhard März² — ¹Technische Physik, Am Hubland, D-97074 Würzburg — ²Infineon Technologies AG, Corporate Research, D-81730 München

Photonic crystal (PhC) waveguides are important building blocks for more complex PhC based devices. An important parameter, especially for passive devices, is the loss of the waveguides. We have investigated the loss of GaAs based photonic crystals at a wavelength of 1.3 µ m. The crystals are realized by an hexagonal array of air holes etched into a GaAs/AlGaAs slab waveguide. Electron beam lithography is used to define the PhC pattern in a resist layer, which is then used to pattern an intermediate SiO₂ mask. The holes are etched into the semiconductor with an Cl₂/Ar based ECR/RIE process. Holes with smooth sidewalls and a depth of 1 µ m are achieved. Measurements of the waveguide losses are performed with an external tunable laser source covering a wavelength range between 1240 and 1340 nm. The losses are determined from the contrast of the Fabry-Perot resonances of the cavity formed by the two cleaved facets and the PhC waveguide. This technique is not sensitive to the coupling efficiency and therefore suitable for PhC waveguides, where efficient coupling to an external source is often a concern. Comparing the losses of waveguides with different lengths, it is possible to extract the waveguide loss per length. The losses of the fundamental mode are about 5.1 db/mm for W3-waveguides (3 rows missing in the PhC lattice) and about 2.5 db/mm for W5-waveguides.