HIGH-CONTRAST, HIGH REFLECTIVITY, OPTICAL MODULATOR USING THE FRANZ-KELDYSH EFFECT IN A THIN-FILM OF GAAS

The bulk Franz-Keldysh effect in a thin film of GaAs is used to demonstrate high contrast ''normally on'' and ''normally off'' optical modulation at 885.2 and 877.5 nm, respectively. The device, a Ag/GaAs/ITO asymmetric Fabry-Perot structure, exhibits a contrast ratio of approximately 75:1 and reflectivity of 32.5% in the normally on mode. This is a demonstration of an asymmetric Fabry-Perot device using the bulk Franz-Keldysh effect. Using the Franz-Keldysh effect makes a larger number of materials and wider wavelength range available for optical modulation than quantum confined effects.