Carrier Concentration Dependent Absorption Spectra of Modulation Doped n-AlGaAs/GaAs Quantum Wells and Performance Analysis of Optical Modulators and Switches Using Carrier Induced Bleaching (CIB) and Refractive Index Change (CIRIC)

Abstract

Optical absorption spectra of modulation doped quantum wells were studied systematically at 77 K and 300 K as functions of the two dimensional electron concentration N _s. It has been found that the absorption at the wavelength of exciton peak is bleached strongly from 2.1×10⁴ cm^-1 to 800 cm^-1 at 77 K as N _s is raised from zero to 1×10¹²/cm²; this is due to the combined effect of exciton quenching and Burstein Moss shift, which override the band gap reduction caused mainly by the many body effect. Performance analysis of quantum well optical modulators and switches using this carrier induced bleaching (CIB) and refractive index change (CIRIC) is presented to show the picosecond switching capability with low drive voltages.