Polymeric Strip Waveguides and their Connection to Very Thin Ultrafast Metal-Semiconductor-Metal Detectors

Abstract

AbstractWe present data on the fabrication process of optical waveguides from four different polymers, which have been patterned either by standard lithographical masking and reactive ion beam etching (RIE) or by direct lithographical exposure of photosensitive material. Three of the resists were directly photosensitive, they could be exposed and developed. Thereafter they can be cured and remain stable. Waveguide losses of 3.5 dB/cm had to be accepted for the photosensitive materials, while the non-sensitive polymers formed very good guides (0.8 dB/cm), but were more difficult to process. We demonstrate the coupling of the strip waveguides to optical fibers on one side and to very thin metal-semiconductor-metal (MSM) photodetectors at the other side. A beam propagation method computer code has been used to evaluate the best coupling efficiencies between the guides and the detectors, which are ultrafast (3.5 ps FWHM) due to their very thin silicon slab design (Si thickness 400 nm, sandwiched between two Schottky contacts).