Polaron effects on the optical absorptions in asymmetrical semi-parabolic quantum wells

The linear and nonlinear optical absorptions considering the weak-coupling electron-LO-phonon interaction in asymmetrical semiparabolic quantum wells are theoretically investigated. The numerical results for the typical GaAs/AlxGa1-xAs material show that the factors of Al content x, the relaxation time and the photon energy have great influence on the optical absorption coefficients. Moreover, the theoretical values of the optical absorptions are more than a factor of 2-3 higher than the one in the structure without considering the electron-LO-phonon interaction by calculating. (C) 2007 Elsevier B.V. All rights reserved.

The origin of the transverse relaxation time in optically excited semiconductor quantum wells

The origin of the transverse relaxation time in optically excited semiconductor quantum wells is investigated based on the vector property of the interband transition matrix elements. The dephasing rate due to carrier-carrier (CC) scattering is found to be equal to half of the common momentum relaxation rate. The analytical expression of the polarization dephasing due to CC scattering in two-dimension is established and the dependence of the dephasing rate Gamma(cc) on the carrier density N is determined to be Gamma(cc) = constant (.) N-1/2, which is used to explain the experimental results and provides a promising physical picture. (C) 2004 Elsevier B.V. All rights reserved.

Efficient InGaAsP/InP multiple quantum well optical phase modulator for the 1.5-1.55μm fiber band

We report an InGaAsP/InP MQW phase modulator operating over the entire 1.55μm fiber band with high phase modulation efficiency and low loss modulation. The spectral dependence of the electro-refraction in a MQW structure is measured for the first time.

Low power all-optical switch in a passive InGaAsP multiple quantum well waveguide

We demonstrate the use of resonant bandfilling nonlinearity in an InGaAsP/InGaAsP Multiple Quantum Well (MQW) waveguide due to photogenerated carriers to obtain switching at pulse powers, which can readily be obtained from an erbium amplified diode laser source. In order to produce gating a polarisation rotation gate was used, which relies on an asymmetry in the nonlinear refraction on the principle axes of the waveguide.

Properties of trench defects in InGaN/GaN quantum well structures

The structural and optical properties of trench defects, which are poorly understood yet commonly occurring defects observed on the surfaces of InGaN multiple quantum wells (MQW), are reported. These defects comprise near-circular trenches which enclose areas of MQW which give rise to a red shift in peak photoluminescence emission and a change in cathodoluminescence intensity with respect to the surrounding material. Atomic force microscopy shows that the height of trench-enclosed areas differs from that of the surrounding quantum well structure, and that trenches are unrelated to the commonly observed V-defects in InGaN films, despite being occasionally intersected by them. Cross-sectional electron microscopy analysis of trenches with raised centres suggests that the red shift in the observed cathodoluminescence peak emission may be due to the quantum wells being thicker in the trench-enclosed regions than in the surrounding quantum well area. The mechanism of trench formation and its implication for the control of the emission properties of light-emitting diodes is discussed. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electroluminescence analysis and simulation of the effects of injection and temperature on carrier distribution in InGaN-based light-emitting diodes with color-coded quantum wells

This paper reports on an extensive analysis of the electroluminescence characteristics of InGaN-based LEDs with color-coded structure, i.e., with a triple quantum well structure in which each quantum well has a different indium content. The analysis is based on combined electroluminescence measurements and two-dimensional simulations, carried out at different current and temperature levels. Results indicate that (i) the efficiency of each of the quantum wells strongly depends on device operating conditions (current and temperature); (ii) at low current and temperature levels, only the quantum well closer to the p-side has a significant emission; (iii) emission from the other quantum wells is favored at high current levels. The role of carrier injection, hole mobility, carrier density and non-radiative recombination in determining the relative intensity of the quantum wells is discussed in the text. © 2013 The Japan Society of Applied Physics.

Dicke superradiance in GaN quantum wells

We numerically modeled the spatio-temporal dynamics of Dicke superradiance in GaN/InGaN heterostructure quantum wells in a ridge waveguide cavity. Model predictions envisage ultrashort pulses of intensities superior to what can be obtained in mode-locked lasers. ©2010 IEEE.