Investigation of etalon effects in GaAs-AlGaAs multiple quantum well modulators

The authors have simulated the modulation properties in transmission and reflection of an electrically active Fabry-Perot etalon containing a GaAs-AlGaAs multiple quantum well pin structure. The calculations are based on measurements of room temperature electro-absorption in a nonresonant device, rather than an empirical model, and generate the optimum values of modulation for any given etalon by selection of the appropriate cavity length. It is found that improved modulation can be obtained compared to the non-resonant device, mainly due to multiple-pass electro-absorption. For example, a device with front and back mirror reflectivities of 0.3 and 0.9 respectively, and a 1 mu m thick multiple quantum well structure, shows a change in reflection from about 75% to 10% at approximately=865 nm when biased from 0 to -10 V. To obtain even higher changes in transmission or reflection and to utilise the electro-refractive properties of the material, high finesse cavities are needed. This however, appears to impose severe constraints on the epitaxial growth accuracy and operational stability of such devices.<>