All-angle negative refraction and active flat lensing of ultraviolet light

Abstract

Decades ago, Veselago predicted that a material with simultaneously negative electric and magnetic polarization responses would yield a 'left-handed' medium in which light propagates with opposite phase and energy velocities--a condition described by a negative refractive index. He proposed that a flat slab of left-handed material possessing an isotropic refractive index of -1 could act like an imaging lens in free space. Left-handed materials do not occur naturally, and it has only recently become possible to achieve a left-handed response using metamaterials, that is, electromagnetic structures engineered on subwavelength scales to elicit tailored polarization responses. So far, left-handed responses have typically been implemented using resonant metamaterials composed of periodic arrays of unit cells containing inductive-capacitive resonators and conductive wires. Negative refractive indices that are isotropic in two or three dimensions at microwave frequencies have been achieved in resonant metamaterials with centimetre-scale features. Scaling the left-handed response to higher frequencies, such as infrared or visible, has been done by shrinking critical dimensions to submicrometre scales by means of top-down nanofabrication. This miniaturization has, however, so far been achieved at the cost of reduced unit-cell symmetry, yielding a refractive index that is negative along only one axis. Moreover, lithographic scaling limits have so far precluded the fabrication of resonant metamaterials with left-handed responses at frequencies beyond the visible. Here we report the experimental implementation of a bulk metamaterial with a left-handed response to ultraviolet light. The structure, based on stacked plasmonic waveguides, yields an omnidirectional left-handed response for transverse magnetic polarization characterized by a negative refractive index. By engineering the structure to have a refractive index close to -1 over a broad angular range, we achieve Veselago flat lensing, in free space, of arbitrarily shaped, two-dimensional objects beyond the near field. We further demonstrate active, all-optical modulation of the image transferred by the flat lens.

Semiconductor-Metal-Semiconductor Core-Multishell Nanowires as Negative-Index Metamaterial in Visible Domain

“…Specifically, in the visible range, negative refraction has been demonstrated using metallic nanowires embedded in a dielectric matrix 3,4 , fishnet structures [5][6][7] , metaldielectric stacks/sandwiches [8][9][10] , planar waveguides 11 and metal-insulator-metal coaxial waveguides 12,13 . Despite the tremendous progress in the design and fabrication of NIM, developing high performance NIM without active loss compensation in the optical domain remains a challenge.…”

Hidden quantum mirage by negative refraction in semiconductor P-N junctions

“…This effect is applicable to either massless or massive electrons in a wide range of materials. It also applies to other matter waves and electromagnetic waves, thus the many experimental platforms [8,13,[24][25][26][27][28][29] that have been used for observing the refocusing by negative refraction for various matter waves could be used to observe this more robust phenomenon.…”

Negative refraction by a planar Ag/SiO2 multilayer at ultraviolet wavelength to the limit of silver

“…That's why planar structures are usually realized in ultraviolet regime. [14][15][16][17] However, in real situation, many of those dielectric materials with high permittivity such as Zinc Oxide or Titanium Dioxide are wide band gap semiconductors that they have strong absorption at wavelengths shorter than their absorption edge (commonly longer than 340 nm), which defines the lower limit of wavelength of effective negative refraction. 14 Therefore, to realize negative refraction at even shorter wavelength is still a challenge.…”