We report results from a symmetric cavity electroabsorption modulator (SCEM) in GaAs/AIGaAs. A reflection change of ,-~45% with an insertion loss of 1.3dB is obtained under 7.5 V in the normally-off mode. We discuss the factors that affect the device performance and compare the attainable performance with that of the normally-off asymmetric Fabry-Perot modulator (AFPM). We also propose a new method for an improvement of the restricted tolerances of SCEMs. Finally, we demonstrate bistable operation using two SCEMs in the symmetric self-electrooptic effect device (S-SEED) configuration, and attempt to evaluate the potential of this type of modulator for SEED applications.
1. I n t r o d u c t i o n
Reflection modulators have a special significance for various data processing applications primarily thanks to their potential for integration in two-dimensional arrays that allows the realization of large-throughput, high-parallelism systems. Fabry-Perot (FP) modulators in particular have attracted a lot of attention as they provide an improvement in performance in comparison with double-pass antireflection-coated devices [1]. The first class of FP reflection modulators relied on the electrorefractive effects in quantum wells (QWs) that result in a shift of the resonant position with bias [2]. Much better modulation and overall characteristics have been obtained with the asymmetric-FP modulator (AFPM) [3,4] where the electroabsorption in QWs is implemented to balance an initially asymmetric cavity (i.e. with front mirror Rf lower than the back Rb). In a similar manner