Electro-optic devices, including modulators and switches

Optical waveguides – Temporal optical modulation within an optical waveguide – Electro-optic

Reexamination Certificate

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C385S008000, C385S040000

Reexamination Certificate

active

07088874

ABSTRACT:
An electro-optical device capable of modulating the amplitude or phase of an optical output in response to an electrical data or control signal, or of switching it, has reduced frequency-dependence and a better combination of operating voltage and bandwidth. It comprises a body of electro-optically active material, waveguides for passing light through the body, and electrodes for applying an electric field with a frequency in the microwave region to the body, and its transverse geometry is such as to maintain adequate phase velocity matching between optical and microwave frequencies. There is a discontinuity in either the body or at least one of the electrodes such that the direction of the electro-optic effect is reversed for a portion of the length of the device at or near its downstream end.The result of such a discontinuity (in combination with phase velocity matching) is that the device operates in three successive zones: in the upstream zone, desirable phase change is induced for all frequencies in the bandwidth of the device; in the middle zone, desirable phase change is induced for frequencies in the upper part of the bandwidth, but phase change in the lower frequencies becomes excessive; while in the downstream zone, there is no significant phase change in the higher frequencies but the excess change at lower frequencies is reversed.

REFERENCES:
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patent: 5005932 (1991-04-01), Schaffner et al.
patent: 5278924 (1994-01-01), Schaffner
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“Wide-bandwidth high-frequency electro-optic modulator based on periodically poled LiNbO3” Y. Lu, et al Applied physics Letters, vol. 78, No. 8 Feb. 19, 2001, pp. 1035-1037.
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“Bandpass Traveling-Wave Mach-Zehnder Modulator in LiNbO3with Domain Reversal” W. Wang, et al IEEE Photonics Technology Letters, Vo. 9, No. 5, May 1997.

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