半导体量子点非本征吸收区的三阶极化率

通过变分法计算了量子点激子基态能量和偶极跃迁振子强度,分析了半导体量子点在非本征吸收区的三阶极化率.量子点中激子的基态能量随量子点半径的增大而单调减小,这是量子尺寸效应的反映;量子点中由基态到激子基态的跃迁振子强度,随量子点半径的增大而单调增大;在弱受限量子点情况下,三阶极化率的实部和虚部都是负的,对应于非线性光学自散焦效应,其绝对值随入射光频率的增加而增加,且随量子点半径的增大而增大.

THE THIRD-ORDER SUSCEPTIBILITY OF SEMICONDUCTOR QDS IN THE NON-RESONANT ABSORPTION REGION

The lowest exciton energy level and the oscillate strength of one exciton in CdS QDs are computed variationally as a function of the quantum dots radius and the third-order susceptibility of semiconductor quantum dots in non-resonant absorption region is studied.The lowest exciton energy decreases as the particle size is increased,which is the effect of the size quantization.The oscillator strength of the lowest excited state of an exciton increases as the particle size is increased.In the weak confinement regime,both the imaginary part and real part of third-order susceptibility are consistently negative,corresponding to self-defocusing nonlinearity;and the absolute value of them increase as the frequency of incident photon,or the particle size,is increased.