Abstract

The approach of microsensing based on integrated optics is very attractive because of the intrinsic features: insensitivity to electromagnetic noise, and ability for non-contact measurements. Fabrication of these devices in silicon-based technology has a lot of follows advantages: good mechanical behavior, availability in large size, low cost of silicon wafers, possibility to hybridize laser diodes directly on the substrate, efficient coupling between optical fibers and silica waveguide, and possible association on the same chip of microinterferometers with other optical components as lenses or beamsplitters. Heterodyne technique can he achieved in an optical waveguide via phase modulation. Usually, this is obtained by altering the refractive index of the guiding region. The induced grating structure causes diffraction of the guided optical wave, resulting in modulation. In silicon, this effect is not possible via electro-optic techniques because of the passive nature of this crystalline material. On the other hand acoustic waves can be used to generate the desired grating pattern in the index profile It is caused by mechanical strain produced by the passage of an acoustical-strain wave. The resulting index variation is periodic, with a wavelength equal to that of the acoustic wave We propose to obtain this effect by deposit of a piezoelectric thin-film transducer on the silicon waveguide.

© 1996 IEEE