Fig. 1. (a) Schematic of the device consists of two horn antennas, uniform gratings, and spot-size converters with a lens. (b) Illustration of the spot-size converter with a lens. (c) Schematic of the fan-beam steering application.

Fig. 2. (a) Simulated coupling efficiency spectrum of grating. The coupling efficiency for different (b) duty cycles and (c) etching depths.

Fig. 3. (a) Calculation and simulation filling factors of each unit. (b) Conversion efficiency of the designed spot-size converter with a lens and the traditional adiabatic converter without lenses of different lengths. (c) Coupling efficiency of the whole structure including two designed couplers connected by a 6 cm long waveguide. (d) Normalized optical power distribution in the device at 192.857 GHz. (e) Input optical field distribution of the spot-size converter. (f) Output optical field distribution of the spot-size converter.

Fig. 4. (a) Optical image of our device with two out-of-plane couplers and a straight waveguide. (b) The optical image of a traditional coupler without a lens. (c) Experimental setup for coupling efficiency measurement of device under test (DUT). (d) Measured normalized coupling efficiency of devices with and without a lens.

Fig. 5. (a) Simulated electric field steering distribution of the beam for frequency variation. (b) The experimental setup of the fan-beam steering. (c) The measured electric field steering distribution of the beam for frequency variation. Measured electric field distributions of the beam at different frequencies of (d) 180 GHz, (e) 190 GHz, and (f) 200 GHz.