PFI:AIR - TT: BaTiO3 Photonic Crystal Electro-optic Devices for 50 GHz Applications

This Accelerating Innovation Technology Project proposes to develop a prototype PhC electro-optic modulator for 50 GHz applications. Future generation systems for high bit rate fiber-optic communication and information processing will require ultra-high bandwidth (100 GHz and beyond) optical components. This includes optical modulators. The prototype can function as building blocks and their integration capability will make sub-terahertz optical modulators readily achievable. Lithium niobate (LiNbO3), the current material of choice for modulators, has high dielectric constants at microwave frequency, which limit the bandwidth of conventional modulators to 40 GHz or less. Approaches based on silicon, indium phosphide and polymeric materials have been widely investigated to solve this major challenge. While progress has been made, a number of significant challenges remain. This project takes an alternative approach by using barium titanate (BaTiO3) ferroelectric oxide thin films with experimentally demonstrated electro-optic (EO) coefficients more than an order of magnitude higher than that of LiNbO3. Furthermore, it has the potential for integration with silicon. The proposed research builds upon Wessels’ group’s extensive research at Northwestern University on nonlinear optical materials and devices under NSF support. EO modulators integrated with two-dimensional photonic crystals (PhCs) have been designed and demonstrated. Using two-dimensional PhCs, and decreasing device length to 1.5 mm, and optimizing design, devices with 50 GHz bandwidth at 1550 nm were recently demonstrated. The footprint of the device is more than a factor of 40 smaller than that of LiNbO3. With proof of concept realized at the chip scale, this project proposes the development of packaged prototype EO modulators using thin film BaTiO3 as the active material. Demonstration of prototypes requires device packaging for high frequency operation, accumulation of technical know-how on improving fiber chip coupling, eliminating electronic parasitics and optical resonances.