Intersubband Absorption in Terahertz Lasers Based on Optically Pumped Quantum Well Structures
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Intersubband Absorption in Terahertz Lasers Based on Optically Pumped Quantum Well Structures Dong-Feng Liu & Jian-Gang Jiang & Jia-Feng He
Received: 23 December 2012 / Accepted: 23 July 2013 / Published online: 8 August 2013 # Springer Science+Business Media New York 2013
Abstract We study the effects of microscopic dynamics of electrons on the intersubband optical absorption in terahertz lasers based on optically pumped quantum wells (THzOPQW). The ensemble Monte Carlo method is used to include different electron scattering mechanisms in the calculation, so that the dependence of intersubband absorption lineshape on microscopic dynamics of electrons can be easily investigated. We find that electronelectron scattering is the dominant factor to determine the absorption linewidth. The real distributions of hot electrons are included to study the temporal changes of the spectra lineshape. Our findings show that the dependence of spectral lineshape on electron population essentially results from the electron scattering and the non-Fermi electron energy distribution. Keywords Terahertz laser . Intersubband optical absorption . Quantum well . Ensemble Monte Carlo
1 Introduction The intersubband absorption in semiconductor quantum wells (QWs) closely relates to fundamental problems in the physics of optical transition, such as relaxation, many-body effects. Terahertz lasers based on optically pumped quantum wells (), which usually use a CO2 [1, 2] or Mid-infrared QCL [3, 4] laser as the excitation source, rely on the intersubband optical absorption to gain the electron population inversion. Therefore, intersubband absorption is a key factor in designing and improving the performance of THz-OPQW. Intersubband absorption lineshape in optically pumped QW has been studied intensively for devices lasing outside terahertz and detecting terahertz, but that in THz-OPQW is still not clear up to now. On the other hand, it is well known that electron-electron (e-e) interaction D.
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