CREOL Researchers Create Integrated Optical Lithium-Niobate-On-Silicon Devices

Researchers at The University of Central Florida (UCF) College of Optics and Photonics (CREOL) have figured out how to coat a silicon chip with a film of the nonlinear optical material lithium niobate (LiNbO₃); the achievement will aid in the creation of integrated photonic circuit components such as low-loss microring resonators and high-performance Mach-Zehnder optical modulators.¹ The work was led by professor Sasan Fathpour.

"Lithium niobate devices are bulky and expensive," says Fathpour. "If thin films of lithium niobate are developed and the geometrical cross-section of the devices on the films can be reduced to submicron dimensions, the field of integrated photonics can move toward a more unifying platform."

Silicon (Si) itself can serve as as the base for many integrated photonics devices; other semiconductors like germanium can be monolithically integrated onto Si to create active devices such as detectors. Of course, Si is also the consummate platform for electronics. The addition of LiNbO₃ to the integrated-photonics “toolbox” can pave the path toward using optics to transmit data between microprocessors, graphics and memory chips in future personal computers, game consoles, laptops, and tablets.

Half-micron-thick LiNbO₃ film
Fathpour and his team managed to bond thin films less than half a micrometer thick of LiNbO3 to Si wafers. The films themselves may have applications other than photonics (microelectromechanical systems, microwave filters for cell phones, and piezoelectric transducers, to name a few). For now, Fathpour’s group is more focused on demonstrating basic integrated photonic devices such as low-loss microring resonators and high-performance optical modulators.

The CREOL group demonstrated electro-optic modulators whose driving voltage is several times less than the best commercial devices, and micro rings with diameters less than a third of a millimeter. All of this will allow integrating several miniaturized modulators and other photonic devices on a single Si chip for advanced communication formats.

The work is funded under the Office of Naval Research Young Investigator Program.

Reference:
¹. Payam Rabiei et al., Optics Express (2013); doi: 10.1364/OE.21.025573