Professor Robert Taylor

Abstract:

To enable the study of cavity quantum electro-dynamical effects in nitride systems, it is essential to be able to fabricate high quality cavity structures that exhibit large Q-values of the order of several thousands. A promising candidate for such a realisation is based around the micro-pillar distributed Bragg reflector (DBR) cavity. The growth of nitride stacks is problematic due to such material issues as lattice mismatch and dislocation propagation which seem to be more pronounced when compared to similar arsenide structures. In this paper we report on our efforts to characterize the homogeneity of our first generation planar DBR structures through both reflectivity measurements using the broadband output of a photonic crystal fiber (PCF) and cryogenic photoluminescence under ultraviolet (UV) excitation. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.

Abstract:

We report on a cavity mode mapping of ZnO tapered nanowires using micro-photoluminescence spectroscopy at room temperature. Both the Fabry-Perot (FP) and the whispering gallery (WG) modes are identified in a single wire. The emission spectra from single nanowires comprise regular Lorentzian peaks, which arise from the FP interference between the ends of the nanowire. The overall intensity along the tapered wire varies periodically. This variation is ascribed to WG mode resonances across the nanowire. The results agree well with the theoretical calculations using the finite-difference time-domain method. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Abstract:

We have investigated, using micro-photoluminescence, the quantum confined Stark effect in an In(x)Ga(1-x)N/GaN multi-quantum disk structure at the tip of a single GaN nanorod. A strong and sharp emission line from the In(x)Ga(1-x)N/GaN quantum disks near 3.26 eV was observed. The peak energy of the emission line was observed to blue-shift with increasing excitation power, indicating a quantum confined Stark effect. Furthermore, both the blue-shift and the intensity of the emission saturate with increasing excitation power. The temperature-dependence of the 3.26 eV emission line has also been investigated.