Ting Xu, Maxim Abashin, Henri J. Lezec
Electric permittivity and magnetic permeability are two fundamental physical quantities for any material. In 1968, Veselago theoretically pointed out a material with simultaneously negative permittivity and permeability would have a negative index of refraction. Although negative index of refraction is not attainable with naturally occurring materials, artificial structures, known as negative index metamaterials (NIMs), exhibit these extraordinary physical properties. In this work, we experimentally demonstrate a quasi-three dimensional all-angle NIM by coupled waveguide array at ultraviolet frequencies. The NIM was fabricated by physical vapor deposition of silver (Ag) and titanium dioxide (TiO2) thin films on a glass slide. Under the illumination at wavelength of 363.8nm, the NIM exhibits isotropic index of -1 within a ±40o angular range. The wide-angle index of -1 is very attractive for constructing Veselago flat lens and realizing super resolution imaging. Moreover, compared with other NIMs, such as fish-net structures, the structures of coupled waveguide array NIMs are much simpler and can be easily fabricated for large area applications.