Ring resonator based electro-optic polymer modulators for microwave photonics applications

This dissertation presents the study of ring resonator based electro-optic polymer optical modulators for microwave photonics applications. Particularly, the work focuses on two important requirements for external modulators in analog optical links: high sensitivity at a high frequency and the linearity of a modulator.; The first portion of this work addresses the analysis of ring modulators in terms of the modulation sensitivity and the modulation bandwidth. The general expression to analyze the modulation frequency response of a ring modulator is derived and applied to traveling-wave ring modulators. The modulators show high modulation efficiency at frequencies around all multiples of the free spectral range, and have better tolerance for the optical/microwave velocity mismatch and microwave loss of the electrode than traveling-wave Mach-Zehnder modulators.; Second, the band operation in an electro-optic polymer ring modulator with a traveling-wave electrode is experimentally demonstrated. The Q of the ring resonator is 45,000 at 1.31 mum, and the electro-optic tuning sensitivity is 1 GHz/V. The modulator shows efficient modulation in a 7 GHz band centered at 28 GHz. This modulation enhancement is due to optical resonance. The device design, fabrication, and characterization are described in detail.; Finally, the linearity of a ring modulator is theoretically analyzed and experimentally studied. It is shown that ring modulators have the potential to obtain a high intermodulation-free dynamic range in sub-octave bandpass optical links, because they have a bias point at which the third derivative of the transfer function is zero; eliminating third-order distortion. The scheme to expand the dynamic range using dual parallel ring modulator is proposed. The experimental result of an electro-optic polymer ring modulator clearly shows a suppression of third-order distortion at a certain bias point, verifying the theory. A linearized ring resonator assisted Mach-Zehnder electro-optic modulator is also analyzed. It is shown that the linearization bandwidth of the modulator is limited by the resonant nature of a ring resonator.