Nonlinear Optical Study of Semiconductor Microstructures, CuCl Quantum Dots, and GaAs Quantum Wells

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Abstract
Nonlinear optical properties of zcro‐dimensional and two‐dimensional semiconductor microstructures, CuCl quantum dots and GaAs quantum wells, are studied with special attention to the bleaching and the blue shift of excitons. In CuCl quantum dots, prominent absorption bleaching of excitons is observed together with a blue shift. The optical nonlinearity is found to increase with an increase of the size of the microcrystals. The blue shift of Z3 exciton absorption increases linearly and becomes saturated with the increase of the excitation density, suggesting the possibility of quantized blue shift. In GaAsAlAs quantum wells, two‐step rise in absorption saturation of the lowest exciton is observed in a few picosecond time domain at 4.2 K under the high‐density band‐to‐band excitation. The former rise takes place simultaneously with the dynamical red shift of the electron‐hole plasma luminescence. The latter rise is accompanied with the blue shift of the exciton. The origin of two‐step rise and blue shift is discussed.