Magnetopolaron effects in light reflection and absorption of a three-level system in a QW

The light absorption {\cal A} and reflection{\calR} coefficients for a three-level system in a quantum well (QW) in a strong magnetic field {\bf H}, directed perpendicularly to the QW's plane, have been calculated. The energy levels correspond to the ground state and to magnetopolaron energy levels \hbar\omega_{1(2)} with the inverse lifetimes \gamma_{r1(2)} and \gamma_{1(2)}. The inverse radiative lifetime of an EHP in a QW \gamma_{r\xi}(\bf{\cal K}_{\perp})\not=0 only under condition {\cal K}_{\perp}\le\omega_\xi n/c, where \hbar\omega_\xi is the EHP energy. It has been shown that \gamma_{r\xi}(\bf{\cal K}_{\perp}) is proportional to H. The values \gamma_{ra}(\bf{\cal K}_{\perp}) and \gamma_{rb}(\bf{\cal K}_{\perp}) for an excitation consisting of a hole and a usual magnetopolaron have been calculated. The index a(b) designates a magnetopolaron upper (lower) term. In the resonance at H_{res}=m_ec\omega_{LO}/|e|~~ \gamma_{ra}^{res}=\gamma_{rb}^{res}=\gamma_{r\xi_0}^{res}/2, where the index \xi_0 corresponds to the EHP with n_e=n_h=1. The dependencies {\cal A}(H)$and${\cal R}(H) for various values of \omega_l in the magnetophonon resonance vicinity have been obtained. The existence of "combined"and "weak" polarons has been predicted. The resonant value H_{res} for the combined polaron case depends on a QW's depth and width.