Silicon-Plasmonic Photodetectors for High-Speed Signal Processing

High-speed photodetectors are core elements of photonic integrated circuits (PIC). If PIC are fabricated on the silicon platform, they must be operated at wavelengths where silicon is transparent. In this case, waveguide-coupled photodetectors made of germanium or III-V materials have to be co-integrated. So far, integrated germanium photodetectors were reported with remarkable optoelectronic bandwidths of up to 250 GHz. However, with a view to terahertz photonics, even higher bandwidths are of interest. For this application, THz carriers can be generated by photomixing, where two lasers with neighbouring frequencies f1 and f2 are superimposed on the detector. The resulting photocurrent oscillates with the difference frequency f1 - f2 in the THz range.
This book introduces and experimentally demonstrates a novel approach for photodetection in silicon by exploiting internal photoemission (IPE) through a monolithically integrated component. We call the resulting device a PIPED (plasmonic IPE detector). It excels with a footprint of 1 µm2, a sensitivity of 0.12 A/W, and a photomixing bandwidth of up to 1 THz, thereby opening an attractive route towards optoelectronic generation and coherent reception of data on THz carriers.