Numerical Modeling of the Emission Characteristics of Semiconductor Quantum Dash Materials for Lasers and Optical Amplifiers

M Gioannini

doi:10.1109/jqe.2004.825201

Abstract

This paper deals with the simulation of the emission characteristics of self-assembled semiconductor quantum dash (QDash) active materials, characterized by high length-to-width and width-to-height ratios of the dash size and by a wide spreading of the dash dimensions. This significant size fluctuation requires to compute numerically the corresponding energy distribution of the electron and hole confined states. Furthermore, due to the long dash length, it is necessary to take into account the many longitudinal confined states that contribute to the emission spectrum. To implement a model that does not require excessive computation time, some simplifying assumptions have been introduced and validated numerically. Starting from good knowledge of the dash size, material composition, and optical waveguide dimensions, we have been able to simulate the amplified spontaneous emission and gain spectra of a quantum dash semiconductor optical amplifier with a good quantitative agreement with the measured data. As an application example, the model is used to predict the gain properties of different QDash ensembles having various size distributions.

Highlights

I N THE LAST decade, a great deal of research on semiconductor materials has focused on the theoretical and experimental study of self-assembled semiconductor nanostructures [1] and has shown the superior electronic and optoelectronic properties obtained by the three-dimensional (3-D) confinement of carriers [2], [3]
We present a numerical model for the calculation of the gain and amplified spontaneous emission (ASE) spectra at different pump rates of a realistic InAs–InP quantum dash (QDash) semiconductor optical amplifiers (SOAs) [13] realized with the QDash material presented in [8]
Since some experimental data relative to the InAs–InP QDash-SOA presented in [35] were available to us, here we present the simulations that have led to the fitting of the measured data

Summary

Introduction

I N THE LAST decade, a great deal of research on semiconductor materials has focused on the theoretical and experimental study of self-assembled semiconductor nanostructures [1] and has shown the superior electronic and optoelectronic properties obtained by the three-dimensional (3-D) confinement of carriers [2], [3]. The carrier confinement in a few bounded states—the ground state and the excited state—in quantum dots (QDs) is obtained by the very small dot size, below or around the exciton Bohr radius. New elongated nanostructures have been grown with quantum dash (QDash) [7], [8] or rod shapes [9]. QDashes appear at scanning and transmission electron microscopy images [8] with a cross section of the same size of QDs (about 2–3 nm 10–20 nm) and a length of hundreds.

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Conclusion