ACOUSTO-OPTICAL PHASED ARRAYS (A-OPA)

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The development of low power and efficient optical interfaces for virtual/augmented/mixed reality (VR/AR/MR), three dimensional holographic displays and solid-state light detection and ranging (LiDAR) systems is a recognized challenge. If overcome, new applications that will ultimately have a transformative impact on our society would be enabled. At the heart of these optical interfaces there is the optical phased array (OPA), a semiconductor-based device that can steer a light beam by controlling the phase of light through tunable components. The OPA demonstrated to date rely either on liquid crystals or integrated photonic platforms with thermal tuning. While compact, these OPAs consume Watts of power. Reducing power consumption of the OPA is the ultimate goal of this project. Through innovations in materials, device design and component integration, this project will investigate the fundamental scientific and engineering challenges behind the development of a new class of OPA, which is dubbed the acousto-optic phased array (A-OPA). If successful, this project will lay the foundations for the development of a new class of OPAs that would facilitate the deployment of efficient optical interfaces for VR/AR/MR, self-driving cars or remote sensor communication. The impact of the A-OPA would be disruptive and transform our interactions with humans and machines. More broadly, the fundamental investigations in materials, devices and technology will impact the photonic community at large by enabling a new host of applications in optical networking, free-space communication, optical switching and interconnects.The proposed A-OPA integrates thin films of lithium niobate (LN), a material with low optical losses, the highest electro-optic coefficient and very large electromechanical coefficient, with arsenic trisulfide (As2S3), a chalcogenide material with relatively low optical losses and one of the highest acousto-optic coefficients. Light is steered along two orthogonal angles by means of the electro-optic effect in LN and the acousto-optic effect in As2S3. The development of advanced micromachining processes permits the integration of these materials in very confined geometries so that light is guided with low loss in sub-micron waveguides and high efficiency electro-acoustic transducers are built on the same chip. Very low voltages and power will be used to steer the phase of light in one direction through the electro-optic effect in LN. The LN on insulator stack will be engineered to efficiently drive acoustic waves into unreleased films of As2S3. By exciting high frequency acoustic waves in As2S3, gratings of variable pitch will be sculpted on the surface of the chip and steer light out of plane. The ultimate technical goal is to devise a high performance OPA with significantly reduced power consumption with respect to the state-of-the-art.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.