Nonlinear absorption in n-i-p-i-MQW structures

Absorptive nonlinearity in a GaAs/AlGaAs n-i-p-i-MQW (multiple quantum well) structure consisting of alternating n-AlGaAs, i-GaAs/AlGaAs MQW, and p-AlGaAs layers is investigated. A change in the absorption coefficient of more than 4000/cm is obtained in the i-MQW layer with an extremely low excitation intensity on the order of 1 mW/cm/sup 2/. The figure of merit for absorptive nonlinearity, sigma /sub ch/, defined as the change in the absorption coefficient induced by excitation of an electron-hole pair per unit volume, is experimentally evaluated to be 7*10/sup -13/ cm/sup 2/, which is an order of magnitude larger than that for saturation of excitonic absorption in a conventional MQW structure. This experimental value agrees well with the theoretical estimation, which is calculated assuming an optical nonlinear process.<
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