Most commercial LIDARs rely on mechanical rotation to steer an optical beam. While this is a consolidated technology, the scanning speed of a mechanical LIDAR may not be enough for demanding technologies such as self-driving cars, autonomous machines and smart communications.
The photonics community is working on realizing optical beam steering by electronically controlling the phase of each individual light emitter (pixel) in an array, inspired by phased arrays in the microwave regime.
LEDs and VCSELs can be used as pixels. However, when arranged in an array, their size leads to a large pitch (spacing between pixels). The large spacing is responsible for grating lobes, which are undesired in LIDARs because they can produce false positives during the scanning process.
Nanophotonics research is offering new ways to realize pixels with a small size such to avoid grating lobes. An example is the concept proposed by A. Cala’ Lesina, et. al. (https://doi.org/10.1109/JSTQE.2020.2991386).
Here, the authors investigate a plasmonic metasurface for beam steering upon reflection. The pixel (unit cell of the metasurface) is composed of a metallic nanoantenna covered by a thin oxide layer, and ITO, thus forming a MOS capacitor. By applying a voltage to the nanoantenna via metallic connectors, a carrier density perturbation is induced over a thin layer (~1 nm) of ITO, thus producing a refractive index variation within the thin layer. Simulations predict control of amplitude and phase of the reflection coefficient of the single pixel by varying the applied voltage. Beam steering is also demonstrated by simulating the full phased array.
More details will be presented at the NUSOD-20 conference.
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