Pyramidal Hyperbolic Metasurfaces Enhance Spontaneous Emission of Nitrogen-Vacancy Centers in Nanodiamond

Nitrogen-vacancy (NV) centers in nanodiamond hold great promise for creating superior biological labels and quantum sensing methods. Yet, inefficient photon generation and extraction from excited NV centers restrict the achievable sensitivity and temporal resolution. Herein, an entirely complementary route featuring pyramidal hyperbolic metasurface is reported to modify the spontaneous emission of NV centers. Fabricated using nanosphere lithography, the metasurface consists of alternatively stacked silica-silver thin films configured in a pyramidal fashion, and supports both spectrally broadband Purcell enhancement and spatially extended intense local fields owing to the hyperbolic dispersion and plasmonic coupling. The enhanced photophysical properties are manifested as a simultaneous amplification to the spontaneous decay rate and emission intensity of NV centers. It is envisioned that the reported pyramidal metasurface can serve as a versatile platform for creating chip-based ultrafast single-photon sources and spin-enhanced quantum biosensing strategies, as well as aid in further fundamental understanding of photoexcited species in condensed phases.