Fig. 1. Scanning electron microscope (SEM) image of the fabricated transversally interleaved phase-engineered antenna. The incident light propagates along the negative x-direction, being diffracted off-chip by the antenna nanostructure. The residual power propagating in the waveguide plane is re-injected to the antenna by a terminal Bragg reflector.

Fig. 2. Schematic of the setup used for the experimental characterization. The TE polarized light is coupled to the chip via the lensed fiber and inverse taper edge coupler. The antenna integrated on the device under test (DUT) diffracts the light upward (red beam), which is subsequently captured by the photodetector (PD). Essential components in the setup include a tunable laser source (TLS), polarization controller (PC), lensed fiber, and power meter.

Fig. 3. Measured and simulated antenna far-field radiation profile along the (a) x-axis and (b) y-axis. The antenna exhibits nearly vertical emission angles in both the x- and y-directions at a wavelength of 1.55 μm, emphasizing its directional characteristics.

Fig. 4. Measured and simulated (3D FDTD) upward diffraction efficiency as a function of the wavelength. The unit of power, dB, corresponds to the absolute loss depicted in Fig. 4. In contrast, in Fig. 3, the power is normalized to zero to facilitate the overlay of the two curves derived from simulation and measurement. This visualization allows a direct comparison of the field-of-view bandwidth between the two datasets.

Fig. 5. SEM image of a 2×4 antenna array along with a schematic sketch of the phased array circuit, including the thermo-optic phase shifters. The antennas are positioned in the array with their Bragg reflectors shared in a back-to-back configuration. The optical distribution networks on both sides are interconnected through a Y-splitter and are further connected to an edge coupler.

Fig. 6. Schematic of the OPA measurement setup. The near- and far-field observations are schematically represented by dash and solid ray tracing, respectively.

Fig. 7. Experimental far-field pattern of the 2×4 phased array (a) before and (b) after the phase calibration. (c) Simulated far field of the array.

Fig. 8. Antenna far field at maximum steering range. (a) Measured and (b) simulated far fields for a π phase shift between adjacent antennas in the x-direction. (c) Measured and (d) simulated far-field patterns for a π phase shift along the y-direction.

Fig. 9. (a) SEM image of the fabricated 8×20 phased array. The inset shows a close-up image of a single antenna. The thermo-optic phase shifters are shown in the blue schematic sketch on the left side of the array. The phase shifters allow for transverse beam steering, i.e., along the y-direction. Measured far-field radiation for Δϕy of (b) random, (c) zero, and (d) π.