  A high-performance wide-angle refractive index sensor based on a simple
onedimensional (1D) metallic deep nanogroove array with high aspect ratio is
experimentally fabricated and demonstrated. The 1D deep groove array is
featured by the excitation of magnetic plasmon (MP), referring to an effective
coupling of incident electromagnetic waves with a strong magnetic response
induced inside the deep grooves. Utilizing the MP resonances that are extremely
sensitive to the surrounding dielectric medium, we successfully achieve a
refractive index sensitivity (RIS) up to $\sim$1300 nm/RIU, which is higher
than that of most experimentally designed plasmonic sensors in infrared region.
Importantly, benefiting from angle-independent MP resonances with strong
confinement of magnetic field inside the deep grooves and strong electric field
localization at the groove openings, we demonstrate wide-angle sensing
capability valid in a broadband infrared region with an excellent linear
dependence on the change of refractive index. Such a MP-based sensor, together
with its simple 1D flat nature and ease of fabrication, has great potential for
practical design of high sensitive, cost-effective and compact sensing devices.
