QUANTUM WELLS IN OPTOELECTRONICS: GaAs/GaAlAs graded index separate confinement single quantum well single-mode waveguide electroabsorption light modulator

A GaAs/GaAlAs graded-index separate confinement single quantum well heterostructure single-mode ridge waveguide electroabsorption modulator was fabricated and investigated. For the modulator with a quantum well width of 100 Å and device length of 700 μm, an on/off ratio of 29.7 dB and estimated absorption insertion loss of 3 dB were obtained for TE polarised light with wavelength 8650 Å, and for TM polarisation the on/off ratio was 28.5 dB. With a switching voltage of 1 V, an on/off ratio of 15 dB was achieved. Photocurrent spectra exhibited a red shift of 600 Å of the absorption edge when the voltage applied to the PIN diode was varied from 0.5 to −7 V. The corresponding shift of the room temperature exciton peak energy was 96 meV.