Calculation Of Photoelastic Coefficients In Multipule Quantum Well Structures In The Reqion Of Resonances of Quasi-Two-Dimensional Excitation Taking into Account Well Width

Abstract

The ideal two-dimensional excition approach was for estimation of photoelastic coefficients in the multiple quantum well structures (MQWS) for the excition resonances region. However for more precisely calculation of photoelastic coefficients it is necessary to take into account the final width of the quantum well. It was made in this work.The analytical expression obtained for linear photoelastic coefficients in the MQWS in the region of resonance of ground excition state was compared with the same value for three-dimensional crystal. It is shown that i n case of MQWS the value of photoelastic coefficients A=2ag3/1,h2 times as much, ag -Bohr radius of three-dimensional exciton, L -the period of MQWS, h -the trual parameter (the wave h c t i o n and quantum well was calculated by variational method). That is under 2ag=L photoelastic coefficients in case of MQWS A=ag2/h2 times as much. For MQWS of system GaAs/Alo 28Gao 72As, width of quantum well -102A, A-1,8.The quantity calculation photoelastic coefficients in MQWS system GaAS/Alo 28Gao 72As in the region of the wave length edge of the excition resonance formed by electron A d h e i v hole was carried out. The dependence of the value of photoelastic coefficients from quantum well width is presented. It is shown, that the photoelastic coefficients 4 times as much of the same value for three-dimensional GaAs in non resonating region of frequency. The photoelastic coefficients have of such big value because in MQWS augmentation of exciton Ridberg constant is lead to development even by room temperature sharply in the stepness of the excition peaks. The strong change of absorption coefficient (and refraction coefficient) are enough for origin large photoelastic coefficients already on the broad curve of the excition absorption and of the transparence region. If an electric field as applied to a MQWS, the photoelastic coefficients increased several times.We draw a conclusion about possibility of using of MQWS as acoustooptic material with a high sigmficance of the photoelastic coefficient and the M2. In the frequency region near the wavelength edge of the quasi-two-dimensional exciton resonance.