Rich 9409122 This NSF Research Initiation Award is aimed at enhancing the understanding of fundamental processes in the carrier dynamics of modulation doped quantum III-V heterostructures. In spatial light modulators (SLMs), strong photo-optic and electro-optic effects which lead to nonlinearities in the optical absorption and refractive index are required to obtain sufficient control of the intensity, phase, or polarization of optical signals. In the proposed work, Professor Dan Rich of USC will study fundamental problems associated with the phenomena of excitation-induced absorption modulation in nipi-doped strained III-V multiple quantum wells (MQWs). The spatially separated electron-hole plasma that can be generated in periodically doped nipi MQW structures exhibits unique electronic and optical properties which can be utilized to fabricated low-power and high-contrast SLMs. Because of large enhancements in the excess carrier lifetime and in-plane ambipolar diffusion constant, large excess carrier concentrations can be created by relatively weak optical excitation to alter the MQW exciton absorption. The PI proposes to study the carrier recombination dynamics of the electron-hole plasma in nipi-doped III-V MQW samples using a novel approach called electron beam- induced absorption modulation imaging (EBIA). In this proposal we will show that EBIA will yield unprecedented um-scale spatial imaging information on the in-plane diffusion processes and recombination lifetimes which govern the performance of optically addressed and electron beam-addressed SLMs. The effects of extrinsic defect- and impurity-related processes associated with dopant interdiffusion and strain-induced misfit formation which can affect the spatial distribution of luminescence and differential absorption in periodic nipi-doped InGaAs/GaAs MQWs will be examined. It is anticipated that a variety of "smart pixel" and Fourier-plane processing photonic technologies will benefit from the proposed work. ***
