Efficient optical coupling between a polymeric waveguide and an ultrafast silicon MSM photodiode

One task of the integration of optoelectronic functions with silicon device s is the construction of an optical waveguide on Si and the optical couplin g of this wa waveguide to a silicon photodetector, We have fabricated polym eric strip waveguides on Si and demonstrate a very efficient design for the optical coupling between the polymeric waveguide and an ultrafast Si-based metal-semiconductor-metal (MSM) mesa-type photodetector, This detector use s high-quality epitaxial Si as the sensitive layer, which is sandwiched bet ween two metallic contacts. If these MSM detectors are excited by a vertica lly incident free beam of lambda = 840 nm and pulses of 100-fs full-width a t half-maximum (FWHM), they respond with electrical pulses of 3.5-ps length (FWHM, T = 300 K).