Experimental Realization of an Epsilon-Near-Zero Graded-Index Metalens at Terahertz Frequencies

The THz frequency band is in many respects the next technological frontier for ultrafast, broadband wireless communication and ultrasensitive biosensing. Challenging goals in these fields demand fresh approaches in electromagnetism research, such as metamaterials. This paper presents an $e{{0}{0ex}}x{{0}{0ex}}p{{0}{0ex}}e{{0}{0ex}}r{{0}{0ex}}i{{0}{0ex}}m{{0}{0ex}}e{{0}{0ex}}n{{0}{0ex}}t{{0}{0ex}}a{{0}{0ex}}l$ demonstration of a fully metallic, epsilon-near-zero (ENZ) graded-index metalens working in the terahertz regime. With a narrow quasisymmetric focus, high power enhancement, and a large focal length, this proof-of-concept lens shows the way for ENZ metamaterial devices based on arrayed waveguides.