Flat collimating lenses based on quasi-conformal transformation electromagnetics

This paper demonstrates two collimating lenses designed using the quasi-conformal transformation optics (TO) technique to radiate multiple directive beams when fed by a simple embedded line source. Using the Finite-Difference Time-Domain (FDTD) method, we perform full-wave numerical simulations to demonstrate their optical performance. Well-collimated beams can be visualized in the near-field region of the TO devices with a corresponding directive radiation pattern demonstrated in the far-field. Thin anti-reflection coatings can be employed to enhance the directivity by reducing reflections at the lens surfaces. These designs only require spatially-varying dielectric materials with no magnetic properties, facilitating low-loss, broadband operation in both the microwave and optical regimes.