Optical waveguides – Directional optical modulation within an optical waveguide – Acousto-optic
Patent
1996-03-29
1997-07-29
Palmer, Phan T. H.
Optical waveguides
Directional optical modulation within an optical waveguide
Acousto-optic
385 11, 385 9, 385 8, 359285, 359308, G02F 100
Patent
active
056528094
ABSTRACT:
An acousto-optical filter (AOTF) having reduced sidelobes. The AOTF is fabricated with a waveguide formed on a substrate along an optical axis. An incoming beam of light is coupled into the waveguide. An acoustic wave beam is induced by an interdigitated transducer. The acoustic wave beam follows an acoustic wave beam axis which crosses the optical axis. The transducer is driven by an externally-generated electric signal. The frequency of the acoustic wave beam is determined by the frequency of the electric signal. The acoustic wave beam induces a diffraction grating in the waveguide as the acoustic wave beam crosses the optical axis, and this in turn diffracts the beam of light. The grating couples the transverse electric and transverse magnetic polarization modes of the light, but only within a narrow band of optical wavelengths. The cross-section of the intensity of the acoustic wave beam can be tapered to further reduce the sidelobes of the passband defined by the frequency of surface acoustic wave beam.
REFERENCES:
patent: 5329397 (1994-07-01), Chang
Arjun Kar-Roy and Chen S. Tsai, "Focused saw induced sidelobe suppression of integrated acousto-optic tunable wavelenghts filters", IEEE 1992 Ultrasonics Symposium. vol. 1, pp. 169,172 No Month.
Integrated Optical, Te-and TM-Pass, Acoustically Tunable, Double-Stage Wavelength Filters in LiNbO; Hermann, H,, et al., Electronic Letters, Mar. 26, 1992, vol. 27, No. 7, pp. 642-644.
L. B. Aronson, G. Rankin, W. R. Trutna, Jr., and D. W. Dolfi, "Reduced sidelobe integrated acouto-optic filter with birefringence apodization"; Optaics Letters, Oct. 15, 1993, vol. 18, No. 20, pp. 1721-1723.
D. A. smith and J. J. Johnson, "Sidelobe suppression in an acousto-optic filer with a raised-cosine interaction strength". Applied Physics Letters, No. 9, vol. 61, Aug. 31, 1993, pp. 1025-1027.
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