Novel Electrically Tunable MSM Photodetector for Resolving WDM Channels

We present a novel MSM (metal-semiconductor-metal) based tunable photodetector for discrimination between two wavelengths with a 365GHz channel spacing. If integrated with CMOS circuits, this photodetector has the potential to perform high-speed channel switching in WDM-based systems. With increasing data traffic load in telecommunications networks, wavelength division multiplexing (WDM) is essential for network capacity and flexibility. Tunable photodetectors that could programmably discriminate the narrowly spaced channels in such WDM system would be very useful for reconfiguring the network. Unfortunately, typical existing tunable filters used for wavelength selection are often mechanically or thermally controlled, leading to slow reconfigurability. In addition, the filters are usually separate components from the photodetectors themselves. Intrinsic wavelength selectivity of the absorption process itself would offer another approach, but that is often restricted to some specific spectral range and can typically not have very narrow channel selectivity. Here, we propose and demonstrate a novel metal-semiconductor-metal (MSM) based tunable photodetector, which enables the filtering function with the detector itself and has the potential to be rapidly electrically tuned simply by changing the MSM finger biasing. This controllable biasing goes beyond previous proposals for fixed multi-finger wavelength detection [1]. Fig. 1: Photograph of fabricated MSM photodetector with 0.8μm finger spacing and