Quantum Optoelectronics

Abstract:

The exact mechanism for non-linear sub-bandgap excitation of single InGaN quantum dots (QDs) has been investigated using interferometric autocorrelation techniques based around a near-infrared (NIR) excitation laser. We identify unambiguously the heavily favoured two-photon absorption (TPA) as being crucial in the observed background reduction for such Nitride structures and compare systematically the relative merits of both the linear (blue) and non-linear (NIR) excitation regimes on several apertures of a masked sample. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Abstract:

We develop an effective way to engineer a two-dimensional GaAs photonic crystal slab with its leaky eigenmodes at desired wavelengths by investigating its spectral dispersion, particularly in terms of transmission efficiency spectra at different launch angles of the light beam. Structural parameters for the photonic crystal slab with leaky eigenmode wavelengths at both 1492 nm and 1519 nm are obtained. This may lead to the enhanced luminescence from erbium-doped trinitride-template fullerenes (Er3N@C80) on the surface of the photonic crystal slabs. © 2009 Elsevier B.V.

Abstract:

Photoluminescence spectroscopic measurements have allowed the acquisition of high resolution spectra at low temperature for the endohedral metallofullerenes, Er2 @ C82 (isomer I) and Er2 C2 @ C82 (isomer I). The characteristic emission in the 1.5-1.6 μm region corresponds to the 4 I13 / 2 (m) → 4 I15 / 2 (n) transitions of the Er3 + ion for both molecules. The emission arising from Er2 C2 @ C82 (I) appears acuminated (narrow lines that taper to a point) when compared with that of Er2 @ C82 (I). The Er2 C2 @ C82 (I) emission linewidths are comparable to those found in crystals, making this molecule of interest for applications where accessible, well-defined quantum states are required. © 2009 Elsevier B.V. All rights reserved.

Abstract:

ZnO nanostructures attract current interest because they have the potential to implement cavity quantum electrodynamics at room temperature. We report a photoluminescence mapping of ZnO nanobelts both at room temperature and 4.2 K. The multicavity modes were observed all over the belt surface, which were induced by Fabry-Ṕrot interference. The emission from the belt surface is enhanced at both the ends and the sides of the belt, and is highly linearly polarized in the direction perpendicular to the long axis of the belt. The results are explained using finite-difference time-domain simulations. © 2009 American Institute of Physics.

Abstract:

We report on the use of interferometric autocorrelation measurements to investigate the non-linear absorption processes evident in single InGaN/GaN quantum dots. The near quadratic excitation intensity dependence of the photoluminescence signal in conjunction with the asymmetric collinear autocorrelation trace unambiguously confirms the process as being one involving two photons via an intermediate virtual state. These results highlight the inherently non-linear optical properties of these structures.