Optimization of terahertz absorption in periodic quantum well structures

Abstract

In this work, the linear absorption spectra for periodic arrays of GaAs-GaAsAl quantum wells with different thicknesses, inside electromagnetic wave has been studied.The eigen energies and eigen functions are calculated by solving the Schrödinger equation numerically. The absorption spectra are obtained using the density matrix approach and the effects of quantum well parameters have been studied. Results show that for a wide range of parameters the absorption peaks lie in the terahertz region. Furthermore, it is possible to adjust the frequency of absorption peak in the terahertz range by changing the width and height of the wells or array numbers that could be used in terahertz devices. PACS numbers: 73.21.Fg, 74.25.Gz Keywords: Double quantum wells, Optical absorption, Triple quantum wells. of electronic devices, optoelectronics, semiconductor lasers, infrared detectors, the study of the external factors on the optical properties of QWs systems is important [7-9].So far, many studies have been carried out to find the linear and nonlinear absorption coefficients of QWs with different shapes [10][11][12][13]. The results of these works show that the absorption coefficients can be very sensitive to various parameters such as applied electric and magnetic fields, incident optical intensity, and the shapes of QWs [12,14]. On the other hand, the terahertz absorber due to its wide applications and also lack of proper high-performance chips has been heavily investigated by scientists in recent years [15][16][17][18]. Usually, the frequency between 0.3 and 30 THz is called the terahertz range [18,19]. Today's, terahertz technology is driven by scientific and industrial applications in areas such as information and communications technology [17], biology and medical science [21], security check and inspection, quality control in production and packaging, detectors, and so on [16][17][18][19][20]. Quantum wells and semiconductors are good candidates for absorber and sensors in the terahertz range [21][22][23].In recent decades, multiple quantum wells have been investigated due to their potential applications (e.g., photo-detectors, high-speed absorption modulators, electro optical switches, and terahertz oscillators) [24]. Technological applications of multiple quantum wells depend on their optical and transportation properties that related to the quantum well specification [25]. The intersubband optical absorption in an asymmetric double quantum well for different barrier widths calculated by Ozturk et al. [26]. The results reveal that the intersubband transitions and the energy levels in an asymmetric double quantum well can be modified and controlled by the barrier and the well width. The sensitivity of the absorption coefficient to the barriers and wells width can be used in various optical semiconductor device applications. 3 Kasapoglu et al. investigated the effects of the geometrical parameters and electric field in a double inverse parabolic quantum well [24]. They indicated that by changing the Al concentrations...