New all-optical reflection modulator using a resonant hetero-nipi Bragg reflector

摘要

Very large fractional reflectivity changes (30%) under optical pump densities of only 3 mW/cm$+2$/ are found in a novel hetero- nipi structure, the Bragg Hetero-nipi Doubly Resonant Optical Modulator (BH-DROM). The high sensitivity of this optical nonlinearity stems from the strong interaction between the excitonic resonances in the quantum well regions of the heteronipi, and an optical Bragg resonance designed into the structure through its optical periodicity. Device response time has been controlled by etching the surface into pixels of various sizes. The measured switching times decrease with decreasing pixel size, with a 50 $mu@m by 50 $mu@m pixel switching in 150 $mu@s. Uniform device switching is ensured by the rapid in-plane transport of carriers through the structure due to the 'Giant Ambipolar Diffusion' mechanism, which has also been studied. A detailed numerical model of this device has been developed which shows good qualitative agreement with the experimental results. Predictions of purely intrinsic bistable behavior and also greatly enhanced contrast ratios and sensitivities are made for similar structures.