Ultralow sidelobe-level integrated acoustooptic tunable filtersusing tapered-gap surface acoustic wave directional couplers |
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Authors: | Kar-Roy A. Tsai C.S. |
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Affiliation: | Dept. of Electr. & Comput. Eng., California Univ., Irvine, CA; |
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Abstract: | We propose a new weighted-coupling scheme using tapered-gap surface acoustic wave directional couplers for realization of ultralow sidelobe-level integrated acoustooptic tunable filters (IAOTF's). Appropriate design analysis has been carried out for 30-mm-long filters operating at an optical wavelength of 1.55 μm in an X-cut Y-propagating LiNbO3 substrate. New synthesized weighting functions have been used for the improvement of sidelobe level suppression over existing single-stage filters by as much as 27 dB. The -20 dB mainlobe width of the resulting IAOTF's varies from 2.7 to 3.9 nm only for the worst sidelobe levels ranging from -30.6 to -44.7 dB, respectively. It has also been shown that further suppression of sidelobe levels by 3-9 dB is possible if the filter is underdriven at 80% mode-conversion efficiency |
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