Dresden 2006 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 18: Symposium Quantum optics in semiconductors II

HL 18.4: Fachvortrag

Dienstag, 28. März 2006, 16:30–16:45, HSZ 01

Imaging the Local Density of Photonic States in Photonic Crystal Nanocavities — •Michael Kaniber, Felix Hofbauer, Simon Grimminger, Max Bichler, Gerhard Abstreiter, and Jonathan J. Finley — Walter Schottky Institut, Am Coulombwall 3, 85748 Garching

We present investigations of the coupling of InGaAs quantum dots (QDs) to both extended and strongly localised optical modes in 2D photonic crystal (PC) nanostructures. The samples consist of a 180nm thick GaAs membrane into which a PC is formed by etching a triangular lattice of air holes. By measuring the local QD spontaneous emission rate (R_spon) we "image" the photonic DOS at frequencies throughout the photonic bandgap (PBG) and close to localised modes at single missing hole defects (Q∼10000, V_mode<0.5(λ/n)³). For QDs emitting into the PBG but detuned from the cavity mode, we observe a strong suppression of R_spon compared to its value in a homogenous photonic environment (R₀/R_spon=30±6) due to the reduced photon DOS. In contrast, for QDs coupled to the cavity modes we measure 1/R_spon∼ 50ps, corresponding to a large Purcell enhancement (R_cavity/R₀=18x).
Single dot measurements reveal clear photon anti-bunching when the emission frequency is detuned from the cavity mode and enhanced photon extraction efficiency (∼30%) due to the PBG which suppresses in-plane emission. Most surprisingly, anti-bunching is not observed for QDs coupled to the cavity modes possibly due to the onset of low threshold lasing.
Supported financially via Sonderforschungsbereich-631