Professor Robert Taylor

Abstract:

A new way of analysing the data in a variable stripe length method gain experiment is presented. The stripe length dependence of the gain is measured in In0.02Ga0.98N/In0.16Ga0.84N multiple quantum wells (MQWs). We confirm that this arises from the change of the chemical potential along the excited stripe due to the interaction of the carrier and photon densities, and the gain threshold density is estimated. Comparison with the PL and PLE spectra suggests that the optical gain arises from weakly localised states in the quantum well in our low-indium-content sample. (C) 2002 Elsevier Science B.V. All rights reserved.

Abstract:

A way of analyzing the data in a variable stripe length method gain experiment is presented. We confirm that the stripe length dependence of the gain in In0.02Ga0.98N/In0.16Ga0.84N multiple quantum wells is caused by the change of the chemical potential along the excited stripe due to the interaction of the carrier and photon densities, and the gain threshold density is estimated. A trial function assuming a Lorentzian line shape for the stripe length dependence of the gain is compared with the edge emission intensity as a function of the stripe length. This is found to fit very well with our data, even beyond the saturation region. © 2001 American Institute of Physics.

Abstract:

The polarization dependence of biexcitonic signals and quantum beats between A-excitons (XA) and A-biexcitons (XAXA) in a high-quality GaN epilayer is measured by spectrally-resolved and time-integrated four-wave mixing. With cross-linear polarised light, mixed beats with two periods are observed: the first beating period corresponds to the energy splitting between XA and XAXA, and agrees well with the calculated XAXA binding energy; while the second beating period corresponds to that between XA and donor bound excitons (D⁰X). The temperature-dependent homogeneous linewidth shows that the D⁰X has a larger acoustic phonon coupling coefficient than the XAXA. We also measured the polarization dependent B-biexciton (XBXB) signal. The effective masses for the A- and B-hole were deduced from the binding energy.

Abstract:

The polarization dependence of biexcitonic signals and quantum beats between A-excitons (X-A) and A-biexcitons (XAXA) in a high-quality GaN epilayer is measured by spectrally-resolved and time-integrated four-wave mixing. With cross-linear polarised light, mixed beats with two periods are observed: the first beating period corresponds to the energy splitting between X-A and XAXA, and agrees well with the calculated XAXA binding energy, while the second beating period corresponds to that between X-A and donor bound excitons ((DX)-X-0). The temperature-dependent homogeneous linewidth shows that the (DX)-X-0 has a larger acoustic phonon coupling coefficient than the XAXA. We also measured the polarization dependent B-biexciton (XBXB) signal. The effective masses for the A- and B-hole were deduced from the binding energy.

Abstract:

We present spectrally resolved and time-integrated four-wave mixing measurements at coherent dynamics of bound excitons in a high-quality GaN epilayer. Coherent excitation, with co-circular polarized light, of the neutral donor-bound excitons (D 0X) and A excitons (XA) results in quantum beats, corresponding to the energy splitting between D 0X and XA. The temperature-dependent dephasing rate is used to deduce the strength of the D 0X-acoustic-phonon interaction via the homogeneous linewidth. © 2001 American Institute of Physics.