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.