University of Delaware - College of Engineering

Dennis Prather, Engineering Alumni Professor

RF-Photonic Integration

This aspect of our research is focused on developing ultra high-frequency (0-300GHz) lithium niobate (LiNbO3) electro-optic (EO) modulators. Historically, LiNbO3 modulators have been used in optical communication networks as they offer wide operational bandwidths, small frequency chirp, capability to handle high optical powers, low optical loss, and stability over an extended period of time. Recent progresses in design and fabrication techniques have allowed LiNbO3 phase modulators to operate over the entire millimeter-wave spectrum (30-300 GHz). However, the challenge remains to package these devices into an integrated module with suitable RF components and antennas.

Our efforts to address this are to design a module that operates from DC through 110 GHz. To this end, the module consists of four integrated elements: (1) a LiNbO3 EO phase modulator, (2) a 1.0mm input coaxial RF connector, (3) an alumina (Al2O3) chip with a coplanar waveguide structure to transition the RF signal from the RF connector to the modulator, and (3) a housing into which the previous three elements are packaged. The 1.0mm RF connector has the advantage of allowing broadband operation over the entire 0-110 GHz frequency range as well as providing an easy way to connect an RF source to the modulator.

In addition, our work consists of reducing the RF insertion loss introduced by the transition from the RF connector to the modulator. To this point, we have developed modules that have an RF insertion loss between 1 and 2.5 dB over a 70-110 GHz bandwidth. This device is bonded to a low-loss optical fiber-to-fiber coupling structure that has a 2.8 dB insertion loss. Since these devices are designed for high-frequency operation, their DC-Vπ is a little higher than most, at 8.5 V, but they offer a Vπ in the order of 20 V at 110 GHz, which is unprecedented.

Recent publications

J. Macario, A. Mercante, P. Yao, A. Zablocki, and D. W. Prather, "Ultra-broadband modulator packaging for millimeter wave applications," IEEE Transactions on Microwave Theory and Techniques, under review.

J. Macario, P. Yao, S. Shi, A. Zablocki, C. Harrity, R. D. Martin, C. A. Schuetz and D. W. Prather, "Full spectrum millimeter-wave modulation," Optics Express, vol. 20, pp. 23623-23629, 2012.

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