Optomechanical antennas for silicon photonic beam-steering

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Photonic circuits - circuits that control light in the way electronic circuits control electrical currents - are a powerful platform for manipulating and processing optical radiation. They have already revolutionized telecommunications by transmitting and receiving our messages, transactions, and multimedia across vast distances. The goal of this project is to extend this revolution deeper into our daily experience: can we use the same photonic circuits to process, detect, and analyze light that is freely propagating in our environment? To do so we will develop an on-chip means of forming and directing a beam of light off of a chip: a microscopic "radar" for optical fields that can sweep a laser beam across a room and also detect light coming from different directions. Our approach uses the fact that acoustic waves, tiny ripples generated on the surface of a chip, can scatter light in very precise and programmable ways. By discovering new ways to shape the propagation characteristics of both the acoustic and optical waves, we endow photonic circuits with the ability to address their surrounding environment in new and powerful ways. Such an advance will enable sensors to perform optical detection and analysis tasks of major importance in domains ranging from consumer electronics to national security. Our work is especially timely considering the growing presence of autonomous systems, such as self-driving cars, drones, and low-power sensors on mobile devices. These emerging technologies necessitate the development of systems such as the one we are developing as mass-manufacturable, ultra-low-power, and efficient optical sensing and communications platforms. Rapid and low-power control over the direction of a radiating light field is a major challenge in photonics and a key enabling technology for emerging sensors and free-space communication links. This program will determine whether optomechanical interactions in guided-wave structures can be used to implement practical and low-cost beam-steering systems on mass manufacturable silicon chips. The resulting devices will demonstrate orders of magnitude lower power and more rapid beam steering than competing approaches. The objective of this research is to develop and demonstrate silicon photonic circuit to steer a radiating optical beam rapidly with low power using guided optomechanical interactions. The approach is to fabricate waveguides that support highly-confined guided optical and mechanical waves with wavevectors matched such that optomechanical scattering couples guided and radiating light fields. To achieve this, silicon nanophotonic design and fabrication techniques will be extended and combined with emerging nanomechanical guided-wave structures and efficient piezoelectric materials to demonstrate revolutionary new beam-steering capabilities. In contrast to previous work, the demonstrated devices, will enable fast and fully 2D beam-steering of a fixed frequency laser. They will also realize simultaneous generation of multiple beams, low electrical/mechanical power consumption, large field of view, high sidelobe suppression, and large bandwidth. These capabilities are well beyond that which is achievable with current chip-based approaches.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.