Excitonic Nonlinear Optical Properties In Quantum Wires and Prismatic Quantum Dots.

摘要

Exciton and biexciton binding energies, and wave functions are calculated with a three parameter variational model in an effective mass approximation for a rectangular GaAs quantum well wire surrounded by an AlGaAs cladding. Moreover, the Al interdiffusion into the wire and the finite band offsets between the wire and the cladding have been included. For the range of dimensions studied, the inclusion of the Al interdiffusion had a pronounced affect on the binding energies when compared to those obtained from the infinite barrier model. In particular, for small (symmetric) wire dimensions the binding energies remain finite. And for asymmetric wires all binding energies were markedly lowered. Using the results of the exciton and biexciton calculation, the third order nonlinear optical susceptibility was calculated as a function of pump probe frequencies in a small range about the exciton absorption resonance. The calculation was restriced to the optical nonlinearity via the biexciton state arising from the population saturation of the exciton state. It was found, depending upon wire dimensions, broadening parameter(s) size, and the amount of pump detuning, values of the imaginary parts of the susceptibilities to be on the order of -.01 to -.1 esu and a fairly large off resonance absorption due to biexciton formation.