Ultralow sidelobe-level integrated acoustooptic tunable filters using tapered-gap surface acoustic wave directional couplers

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 wa...

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Bibliographic Details
Published in:Journal of lightwave technology 1994-06, Vol.12 (6), p.977-982
Main Authors: Kar-Roy, A., Tsai, C.S.
Format: Article
Language:English
Subjects:
Acoustic waveguides
Acoustic waves
Directional couplers
Fabrication
Optical crosstalk
Optical design
Optical filters
Optical surface waves
Optical waveguides
Surface acoustic waves
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Summary: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 /spl mu/m in an X-cut Y-propagating LiNbO/sub 3/ 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.< >
ISSN:0733-8724
1558-2213
DOI:10.1109/50.296187