As optical phased arrays (OPAs), used as solid-state beam scanning elements, swiftly stride towards higher efficiency and faster scanning speed, the line beam scanner is emerging as a viable substitute for its counterpart relying on point-beam-incorporated raster scanning. However, line-beam scanners require active phase shifters for beam scanning; thus, they consume more power and have complex device designs. This study proposes and demonstrates a dispersive silicon–nitride OPA that allows for passive wavelength-tuned steering of a line beam with an elongated vertical beamwidth. To steer the line beam passively covering the two-dimensional field of view, we deployed an array of delay lines with progressive delay lengths across adjacent channels. Furthermore, adiabatic tapers that allow precise effective array aperture adjustment are used as emitter elements to flexibly realize different vertical beamwidths. Combinations of different delay-length differences and taper tip-widths resulted in beam coverage (lateral × vertical) ranging from 6.3° × 19° to 23.8° × 40° by tuning the wavelength from 1530 to 1600 nm. The main lobe emission throughput was as small as − 2.8 dB. To the best of our knowledge, the embodied OPA is the first demonstration of a passive line beam scanner facilitating an adjustable beam coverage with quick operation and enhanced efficiency.

We propose and design a flat optical phased array (OPA) receiver that consists of a grating antenna, a free-propagation region (FPR) incorporating an on-chip metalens concentrator (OCMC), and an output port of a tapered waveguide. By concatenating the OCMC-integrated FPR with the antenna, the proposed OPA allows light coupled at a slanted ψ angle to be conveyed to the output, thereby resolving the challenges of phase-controlled light detection. To impose a space-dependent phase on the incident light from the antenna, the OCMC is constructed by laterally arranging subwavelength slot meta-atoms with varying slot lengths, which are created in the core layer of a slab and uniformly quantized at 16 phase levels. Hence, without the aid of phase modulators, the light beam emerging from the grating antenna can be focused on the output port through angle-tolerant coupling along the lateral direction. The miniaturized OCMC was confirmed to play a pivotal role in achieving enhanced in-plane coupling efficiency over the field of view.

Conventional OPAs incorporating a diffraction grating were mainly developed to achieve a two-dimensional spot beambased scan, which inevitably requires a wide range of wavelength tuning, leading to unaffordable complexity and limited scanning speed. In this study, we demonstrate a hybrid OPA that capitalizes on a silicon nitride line beam emitter based on tapered waveguides array, which facilitates efficient line beam scanning exhibiting flexible vertical field-of-views (FOVs) at a wavelength of 1550 nm. The line beam is horizontally scanned by driving an array of hybrid-integrated thermo-optic polymer phase modulators. The vertical FOV can be flexibly adjusted by varying the tip widths of the tapers and thus the angular divergence of emitted beams, leading to flexible FOVs ranging from 30°× 14°to 30°× 47°. A lens module is particularly devised and tethered to the OPA, thereby further tailoring and amplifying the FOVs along vertical and horizontal directions. The proposed hybrid OPA in conjunction with a lens module was practically manufactured to efficiently substantiate desired line beam scanning, achieving FOVs ranging from 51°× 0.6°to 51°× 10.3°. The developed line-beam-based OPA is anticipated to play an integral role in embodying an advanced LiDAR system featuring fast beam scanning.

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