Reconfigurable Silicon Photonic Circuits Provide Control of Light Patterns

The ability to control light in a silicon chip could enable novel applications in programmable photonic circuits, including applications for optical testing and data communication. The development of flexible integrated-optic circuits that can be externally controlled was made possible using an all-optical spatial light modulator (SLM) to reconfigure photonic devices, making them capable of routing the flow of light.

Artistic rendering of a silicon-on-insulator 1×2 multimode interference splitter with a projected pattern of perturbations induced by femtosecond laser. The perturbation pattern achieved routing of light to a single output port with 97 percent efficiency. Courtesy of the University of Southampton.

Researchers at the University of Southampton and the Institut d’Optique in Bordeaux, France, demonstrated that light could be routed between the ports of a multimode interference (MMI) power splitter with more than 97 percent total efficiency and negligible losses. The intricate interplay between many modes traveling through the MMI was dynamically controlled. A pattern of local perturbations, induced by femtosecond laser, was used to shape the transmitted light, demonstrating that all-optical wavefront shaping in integrated silicon-on-insulator photonics devices is possible.

By employing UV pulsed laser excitation to modify the spatial refractive index profile, the research team was able to maintain control of the optical transfer of telecommunication-wavelength light traveling through the device, thus allowing the functionality of the light to be redefined.

Photonics chip functionality is typically hardwired. Reconfigurable optical elements that would provide the ability to freely route light in a static silicon element offer an important building block for field-programmable photonics, the researchers said.

"We have demonstrated a very general approach to beam shaping on a chip that provides a wide range of useful functionalities to integrated circuits,” said research fellow Roman Bruck. “The integrated spatial light modulator turns conventional silicon photonics components into versatile reconfigurable elements."

Future applications of this technology may include all-optical reconfigurable routers, ultrafast optical modulators and switches for optical networks and microwave photonic circuits, as well as wafer-scale optical testing of photonic chips. Silicon photonics form the backbone of next-generation on-chip technologies and optical telecommunication, which are aimed at a wide range of emerging applications including optical interconnects, microwave photonic circuits and integrated optical sensors.

The research was published in Optica, a publication of the Optical Society (OSA) (doi: 10.1364/optica.3.000396).