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Bau Quang Nguyen,Hung Manh Do,Ngoe Bich Nguyen 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.2
Analytic expressions for the nonlinear absorption coefficient of a strong electromagnetic wave (laser radiation) caused by confined electrons for the case of electron - optical phonon scattering and electron - acoustic phonon scattering in quantum wells are calculated by using the quantum kinetic equation for electrons. The problem is also considered for both the absence and the presence of an external magnetic field. The dependence of the nonlinear absorption coefficient on the intensity and the frequency of the external strong electromagnetic wave, the temperature T of the system and the cyclotron frequency for case of an external magnetic field is obtained. The analytic expressions are numerically evaluated, plotted and discussed for a specific quantum well AlAs/GaAs/ AlAs. The computations show that the nonlinear absorption coefficient in quantum wells is much more greater than to is in normal bulk semiconductor. The appearance of an external magnetic field causes surprising changes in the nonlinear absorption. All the results are compared with those for the normal bulk semiconductors to show the difference.