Effect of outermost layers on resonant cavity enhanced devices

Abstract

Both the reflectivity and the reflection delay of a quarter wave mirror (QWM) can be controlled by choosing the outermost layer of the QWM appropriately. For a GaAs/Al0.75Ga0.25As QWM, depositing a Si layer as the incoming outermost layer decreases the reflectivity to the same degree as removing 19.6 layers, and increases the reflection delay by 12.0 times. Likewise, when using a TiO2 layer, the reflectivity decreases to a level similar to the removal of 16.1 layers while the reflection delay is 7.9 times longer. Therefore, an efficient method to fabricate resonant cavity enhanced photodetectors for bidirectional optical interconnects is proposed. This method needs no subsequent etching process while giving a quantum efficiency of approximately 90% using currently available deposition techniques. Furthermore, the tunable wavelength and bandwidth ranges of microelectromechanical system tunable filters can be controlled separately by the outermost layer, thereby allowing filters with different bandwidths to be fabricated on the same wafer.