Abstract

Numerous fast semiconductor photodetectors have been developed in the last decade. These devices have used short carrier lifetimes^1,2 or large electric fields and small geometries^3,4 to produce fast impulse responses. In contrast to these methods of making fast photodetectors, we propose a photovoltaic device whose operating speed is due to diffusion of carriers. This device involves interfering light waves to form a grating of photoexcited carriers with a sinKx spatial dependence. Such a distribution will decay with a time constant of (DK²)⁻¹, where D is the material’s diffusion constant. Because K can be made very large, the response time can be extremely short. If the grating is formed in silicon, for example, with optical beams of 1 μm wavelength having antiparallel k-vectors, then the diffusion-driven detector response time will be 0.25 psec.

© 1985 Optical Society of America