IMPROVED SWITCHING PERFORMANCE OF MULTIPLE-QUANTUM-WELL ASYMMETRIC FABRY-PEROT ULTRAFAST ALL-OPTICAL SWITCH BY COUPLED-CAVITY CONFIGURATION

We show theoretically that mode splitting of a vertical coupled-cavity is very effective for realizing high contrast and lossless operation in asymmetric Fabry-Perot all-optical ultrafast time-division switches having a multiple quantum well saturable absorber. The merit of the c oupled-cavity is mode splitting, which makes pump and signal pulse fre quencies independently adjustable without lengthening of cavity; the s hort cavity feature is indispensable for fast response with high sensi tivity. With 7.7 fJ/mu m(2), a 0.2 dB internal loss is achieved for a coupled-cavity, while a conventional single cavity has a loss of 17 dB . The maximum extinction ratio for a coupled-cavity reaches 32 dB, whi le that for a single cavity saturates at around 22 dB.