Design of 2D-Scanning Bifocal Metalens Antenna Using ControlNet-Enabled Stable Diffusion Deep Generative Model

We present a low-cost, low-profile, high-gain, 2D-scanning bifocal metalens antenna for 5G/6G communication applications. First, we employed the ControlNet-enabled stable diffusion technique to generate a set of low-loss, wide-phase-range pixelated unit cells. Second, we generalized the 1D-scanning bifocal metalens phase distribution formula for use in 2D-scanning applications. Finally, the ControlNet-enabled stable diffusion generated unit cells are used to synthesize the metalens capable of 2D-scanning using the generalized 2D-scanning bifocal phase distribution formula. The synthesized antenna with diameter (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</i>) of 300 mm, focal length (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i>) of 150 mm, and an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i>/<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</i> ratio of 0.5 is capable of having a scan beam range up to ±23.3° with a scan loss of ~3 dB in both principal cuts. This enhancement in scan loss performance by ~0.6 dB surpasses that of traditional center-fed, single-focus, spherical-wave phase-compensated metalenses and offers performance that is better than other 1D-scanning designs. This is accomplished while upholding a measured high peak aperture efficiency of 44.8% and a 3-dB gain bandwidth of 16.5%. Most importantly, our work is the first to generalize the 1D-scanning bifocal phase distribution formula for use in the design of a 2D-scanning bifocal metalens.