Non-linear optical devices utilizing triply coupled asymmetric GaAs quantum wells

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The semiconductor quantum well has been expected to be one of the components in the field of opto-electronic devices with high speed, high density and high sensitivity. In this study, the resonance phenomena in a coupled quantum well system is investigated in terms of the tunneling of carriers to develop a ultra-high speed optical switching device.(1)The transmission in a asymmetrically coupled triple quantum wells made by GaAs/AlGaAs hetero-structure exhibited a strong nonlinear behavior as a function of the incident optical intensity. It was dependent on the wavelength, determined by the relative widths of the quantum wells.(2)The femo-second pump-probe method was applied to investigate the response of the device, It was shown that the non-linear behavior occurs within a few pico-seconds.(3)The response of the transmission and flenectance were investigated as a function of the wavelength of the incident laser light. At a wavelength which corresponding to the narrowest well exciton, the carrier density was found to decrease with a time constant of 3-4 ps. On the other hand, at a wavelength corresponding to the widest well exciton, the carrier density increased with a time constant of 4-5 ps. This suggests the occurrence of the electron transfer between these wells. This proves that the nonlinear behavior is due to the different tunneling time of electrons from that of holes.(4)The Stark shift of the PL spectra showed one to one correspondence to the non-linear behavior of the transmission.