tailieunhanh - Ability to increase a weak electromagnetic wave by confined electrons in doped superlattices in the presence of laser radiation modulated by amplitude

The analytic expressions for the absorption coefficient (ACF) of a weak electromagnetic wave (EMW) caused by confined electrons in the presence of laser radiation modulated by amplitude in doped superlattices (DSL) are obtained by using the quantum kinetic equation for electrons in the case of electron–optical phonon scattering. | JOURNAL OF SCIENCE OF HNUE Mathematical and Physical Sci. 2012 Vol. 57 No. 7 pp. 113-123 This paper is available online at http ABILITY TO INCREASE A WEAK ELECTROMAGNETIC WAVE BY CONFINED ELECTRONS IN DOPED SUPERLATTICES IN THE PRESENCE OF LASER RADIATION MODULATED BY AMPLITUDE Nguyen Thi Thanh Nhan1 Nguyen Vu Nhan2 and Nguyen Quang Bau1 1 Faculty of Physics College of Natural Sciences Hanoi National University 2 Faculty of Physics Academy of Defence force - Air force Abstract. The analytic expressions for the absorption coefficient ACF of a weak electromagnetic wave EMW caused by confined electrons in the presence of laser radiation modulated by amplitude in doped superlattices DSL are obtained by using the quantum kinetic equation for electrons in the case of electron optical phonon scattering. The dependence of the ACF of a weak EMW on the temperature frequency and superlattice parameters is analyzed. The results are numerically calculated plotted and discussed for n-GaAs p-GaAs DSL. The numerical results show that ACF of a weak EMW in a DSL can get negative values. So by the presence of laser radiation modulated by amplitude in some conditions the weak EMW is increased. The results also show that in some conditions the ability to increase a weak EMW can be enhanced in comparison with the use of non-modulated laser radiation. This is different from the case of the absence of laser radiation modulated by amplitude. Keywords Absorption coefficient doped superlattices weak electromagnetic wave laser radiation. 1. Introduction In recent times there has been a growing interest in studying and discovering the behavior of low-dimensional systems in particular DSL. The confinement of electrons in these systems considerably enhances electron mobility and leads to their unusual behaviors under external stimuli. As a result the properties of low-dimensional systems especially the optical properties are very different in comparison with those of normal .