OPTICAL FILTER ADJUSTABLE BY ACOUSTOOPTIC AL INTERACTION COLINEAR WITH SURFACE-WAVES

Acousto-optical mode convecters are the basic elements for a variety o f integrated optical circuits. It has been demonstrated that efficient acousto-optical mode converters with a large tuning range and low dri ve power can be realized in a combined structure of acoustical and opt ical waveguides. We use an acoustical directional coupler to obtain a weighted coupling resulting in a theorical filter response with large sidelobe suppression. Nearly 100% TE/TM polarization conversion effici ency was achieved using only 3 mW of applied RF power in a 1.52 mum fi lter of 2 nm optical bandwidth on a cristal of LinbO3. Yet, the absolu te sidelobe levels were significantly higher than expected. This is pr esumably due to nonuniformity in the effective birefringence of the op tical waveguides.