Harnessing the Diamond–Air Interface as an Efficient Photon Antenna for Solid-State Emitters

Extracting photons from defect centers is challenging
due to the
high refractive index of typical substrates. For nitrogen-vacancy
centers in diamond, reaching saturation count rates above 2.5 ×
105 counts/s so far requires nanofabricated optics, such
as diamond waveguides or solid immersion lenses. Here, we present
an experimental and theoretical study of defect center emission at
unmodified planar dielectric surfaces by quantitative back-focal-plane
imaging and analytical modeling. Our results indicate that photon
count rates approaching those of nanofabricated optics can also be
achieved by oil-immersion optics. This is due to a dielectric antenna
effect, which directs the majority of the emission into the substrate
within a narrow angle window suitable for back-side collection. By
quantification of the collection efficiency of back-side detection,
our work also enables a novel measurement method for the quantum efficiency
of shallow defect centers. Its result challenges established values.
Possible reasons for the discrepancy are discussed.