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Improved performance of traveling wave directional coupler modulator based on electro-optic polymer

TitleImproved performance of traveling wave directional coupler modulator based on electro-optic polymer
Publication TypeConference Paper
Year of Publication2012
AuthorsZhang, X., B. Lee, C-Y. Lin, A. X. Wang, A. Hosseini, X. Lin, and R. T. Chen
Conference NameSPIE OPTO Optoelectronic Interconnects XII
Pagination82671B - 82671B-11
Date Published01/2012
PublisherSPIE
Conference LocationSan Francisco, California
Abstract

Polymer based electro-optic modulators have shown great potentials in high frequency analog optical links. Existing commercial LiNibO3 Mach-Zehnder modulators have intrinsic drawbacks in linearity to provide high fidelity communication. In this paper, we present the design, fabrication and characterization of a traveling wave directional coupler modulator based on electro-optic polymer, which is able to provide high linearity, high speed, and low optical insertion loss. A silver ground electrode is used to reduce waveguide sidewall roughness due to the scattering of UV light in photolithography process in addition to suppressing the RF loss. A 1x2 multi-mode interference 3dB-splitter, a photobleached refractive index taper and a quasi-vertical taper are used to reduce the optical insertion loss of the device. The symmetric waveguide structure of the MMI-fed directional coupler is intrinsically bias-free, and the modulation is obtained at the 3-dB point regardless of the ambient temperature. By achieving low RF loss, characteristic impedance matching with 50Ω load, and excellent velocity matching between the RF wave and the optical wave, a travelling wave electrode is designed to function up to 62.5GHz. Domain-inversion poling with push-pull configuration is applied using alternating pulses on a 2-section directional-coupler to achieve a spurious free dynamic range of 110dB/Hz<sup>2/3</sup>. The 3-dB electrical bandwidth of device is measured to be 10GHz.

DOI10.1117/12.907744