Abstract

Recently, GaAs pyramids standing on top of distributed Bragg reflectors (DBRs) have been studied as candidates for high-quality (Q) and low mode-volume optical cavities [1, 2]. Their fabrication through a wet-chemical etching process allows an easy geometrical tuning of pyramid size and facet angles. Q factors reaching 700 have been observed by micro-photoluminescence measurements [2]. While these previously investigated pyramid structures rely on total internal reflection at the facets and a DBR at the base plane, two novel designs of pyramidal structures are suggested in this contribution in order to enhance light confinement. On the one hand, freestanding reversed pyramids have been realized as shown in Fig. la. In such structures, light confinement is based exclusively on total internal reflection. Calculations based on finite-element methods suggest potentially very high Q factors for such geometries, especially for pyramids with an octagonal base (feasible with the same method). On the other hand, truncated pyramids standing on top of a DBR have been metallized or overgrown with another DBR as proposed in Ref. [2]. In contrast to freestanding pyramids the latter approach implies that both vertical as well as lateral light confinement are achieved by DBRs (see cross-section in Fig. 1c).

© 2009 IEEE