Tunable electroabsorption in gallium arsenide doping superlattices

Tuning of the optical absorption coefficient by electrical bias in doping superlattices (n-i-p-i crystals) is demonstrated for the first time by both photoconductivity and transmission measurements at room temperature. The absorption coefficient at 1.04 μm obtained from the photoconductivity measurement varies by a factor of 240 when the p-n junction bias is changed from 0.4 to −1.5 V. A change of transmission up to 22% at 0.89 μm wavelength through a 2.1-μm-thick n-i-p-i crystal is achieved by varying bias merely between 0.6 and −2.0 V. Moreover, the change of transmission is nearly linear with p-n junction bias.