2 December 1992 Space harmonic analysis of integrated optic modulators with periodic electrodes
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Abstract
The frequency response of integrated optic modulators with traveling wave electrodes is limited by the phase velocity mismatch between the optical and RF signals. At millimeter wave frequencies the short electrodes that must be used to avoid this phase mismatch severely reduce the modulator sensitivity. One approach that provides high frequency modulators with increased sensitivity is the use of periodic intermittent interaction (PII) electrodes and enhanced periodic phase reversal (EPPR) electrodes. In this paper, the RF signal on the electrode is represented as a summation of traveling wave space harmonics. The electrode geometry is adjusted so that the phase velocity of the dominant space harmonic equals the phase velocity of the optical signal at the design frequency. General velocity-matching conditions are derived for both the PII and the EPPR modulators; the bandpass frequency response is then calculated by adding the individual responses of all space harmonics traveling down the electrode. Design examples are provided of periodic electrodes for LiNbO3 and GaAs modulators for operation at 35 GHz. Finally, a practical method for velocity-matching is described that requires only the two-port characterization of an individual electrode unit section.
© (1992) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
James H. Schaffner, "Space harmonic analysis of integrated optic modulators with periodic electrodes", Proc. SPIE 1703, Optical Technology for Microwave Applications VI and Optoelectronic Signal Processing for Phased-Array Antennas III, (2 December 1992); doi: 10.1117/12.138391; https://doi.org/10.1117/12.138391
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