Title :
Surface-acoustic-wave directional coupler for apodization of integrated acoustooptic filters
Author :
Smith, David A. ; Johnson, John J.
Author_Institution :
Bellcore, Red Bank, NJ, USA
Abstract :
A SAW waveguide directional coupler that was used to provide a raised-cosine apodization of the SAW beam intensity, in order to achieve sidelobe suppression of an integrated acoustooptic filter, is demonstrated. The SAW guide coupler consisted of two closely spaced, evanescently coupled parallel acoustic waveguides. A single guided SAW mode was excited by a miniature transducer imbedded in a 100- mu m-wide waveguide, and in excess of 99% of the SAW energy was transferred from the original waveguide to the coupled guide, and back, across a gap of 20 mu m. The coupling length (for complete crossover) was 9.8 mm and depended exponentially on gap, as expected. This SAW coupler resulted in 10-dB sidelobe suppression compared to an unapodized acoustooptic filter.<>
Keywords :
acoustic waveguides; acousto-optical devices; directional couplers; integrated optics; optical filters; surface acoustic wave devices; 10 dB; 100 micron; 20 micron; 9.8 mm; 99 percent; SAW beam intensity; SAW energy transfer; SAW guide coupler; SAW waveguide directional coupler; apodization; coupling length; evanescently coupled parallel acoustic waveguides; gap; integrated acoustooptic filter; integrated acoustooptic filters; raised-cosine apodization; sidelobe suppression; single guided SAW mode; surface acoustic wave coupler; Acoustic waveguides; Acoustic waves; Directional couplers; Optical attenuators; Optical films; Optical filters; Optical polarization; Optical surface waves; Optical waveguides; Surface acoustic waves;
Journal_Title :
Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on
