Light detection in dielectric waveguides by a photodiode through direct evanescent field coupling

Abstract

Though LiNbO3 and LiTaO3 have excellent electro-optic properties, they are insulators and therefore do not lend themselves for the realization of an efficient photodetector scheme. Using the idea of evanescent coupling we propose and demonstrate a convenient and efficient light detection scheme to be used with a variety of dielectric waveguide devices. The scheme utilizes an etched mesa photodiode fabricated in silicon, evanescently coupled to a waveguide for light detection. The high detection sensitivity (0.3 mA/mW at λ=6328 Å) and the possibility of incorporating integrated circuits on a common substrate (in Si or GaAs) make the scheme very attractive for hybrid integration of thin-film optical and electronic devices.