GaAs体材料及其量子阱的光学极化退相特性

Mechanism of optical polarization dephasing in bulk GaAs and multiple quantum wells

采用飞秒时间分辨瞬态简并四波混频技术 ,在室温下测量了GaAs体材料及其量子阱材料GaAs Al0 3Ga0 7As的光学极化超快退相时间 ,当激光中心波长为 785nm ,受激载流子浓度为 10 1 1 cm- 2 时 ,它们的退相时间分别为 2 8fs和4 6fs.量子阱材料的退相时间比体材料的长 ,这是由于量子阱中的载流子在垂直于GaAs AlGaAs界面的运动受到限制 ,运动呈现二维特性 ,大大减小了载流子的散射概率 .实验中观察到瞬态简并四波混频信号的强弱与入射光的强度和偏振方向有关 。

The optical polarization dephasing times in bulk GaAs and GaAs/Al 0.3Ga 0.7As quantum wells at room temperature are measured using time-resolved degenerate-four-wave mixing (DFWM). Under the conditions of excitation pulse central wavelength of 785nm and carrier density of 10 11cm -2, the dephasing times of 28 and 46 fs for bulk GaAs and multiple quantum wells, respectively, are measured. Because the carrier-carrier scattering rate in quantum wells is reduced due to the confinement of the carrier behavior,the dephasing time of the quantum wells is longer than that of bulk. The dependence of the DFWM signal on the intensity and the polarization of the incident pulses is evaluated by a theoretical model of third-order nonlinear density matrix.