Liquid crystals provide compact and efficient reconfiguration capabilities to visible wavelength optical phased arrays (OPAs), which have been limited in scale for beam forming and steering. Many visible wavelength applications require compact optics to densely route and pattern light including AR/VR, underwater wireless communications, biological stimulation and imaging, and quantum information systems based on trapped-ions, neutral atoms, and color centers. Silicon nitride photonic integrated circuits have made significant progress due to their wide transparency window down to blue wavelengths, low waveguide propagation losses, and mature foundry-compatible fabrication processes. However, the platform has primarily relied on thermo-optic phase shifters for reconfiguration, which consume milliwatts of power per element limiting the scale and complexity of optical patterns produced by OPAs. Notaros et al. demonstrate, for the first time, visible light beam steering using an OPA based on liquid crystal phase modulators on the silicon nitride platform with footprints below tens of microns, low drive voltages, and minimal static and dynamic power consumption. The birefringence of the liquid crystals leads to a large electro-optic phase modulation as the liquid crystals are actively aligned within the evanescent field of the waveguide. To demonstrate its use for underwater wireless communication, the authors demonstrate transmission of a 1 Gbps signal through water that is switched between multiple receiving points using the OPA.

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