Phase-dependent intersubband optical properties of asymmetric AlGaAs/GaAs coupled quantum wells

Abstract

In this article, we have investigated the optical properties of intersubband transitions in an asymmetric AlGaAs/GaAs coupled quantum wells system. We solved the Schrödinger equation numerically using homemade finite difference codes to determine the electronic structure. The susceptibilities were calculated in frame of density matrix equations. The effect of relative phase variation between applied fields, on the linear absorption coefficients, relative refractive index changes, and group velocity has been investigated. The results show that the linear optical properties are extremely phase-dependent. By adjusting the phase, it is possible to obtain absorption curves with dispersion-like profile and vice versa.Keywords: coupled quantum well; relative phase effect; dispersion-like and absorption-like profiles; interssubband optical properties IntroductionSemiconductor nanostructures, such as quantum dots (QDs) and quantum wells (QWs), approach the quantum information to leverage industry's vast technological infrastructure and integrate with existing information and communication technologies [1]. Those structures have received considerable attention for their applications in high-tech electronics and optoelectronics devices such as optical modulators, switches, detectors, and sensing [2][3][4]. The GaAs-based devices potentially have great advantages such as high electron mobility, high thermal stability, low noise, and wide temperature operating range [5,6]. The GaAs QW is tunable of the range of optical wavelengths that can be emitted and absorbed. Therefore, the growth of GaAs-based materials on various substrates is extensively studied and a wide range of optical wavelength engineering is being achieved.In the past two decades, coherent quantum processes have taken into consideration. Quantum interference and coherence can generate some interesting phenomena such as electromagnetically induced transparency (EIT) [7], enhancement of refractive index [8][9][10], optical bistability [11], Kerr nonlinearity [12,13], four-wavemixing [14][15][16][17], optical switching [18,19], and generation of optical solitons [20]. One area of current interest in optical physics of asymmetric coupled quantum wells (CQWs) is measuring coherent quantum processes [21]. A particular example of this is work on terahertz oscillations excited by short optical pulses [22], in which one