33 research outputs found
Observation of the Magneto-Optic Voigt Effect in a Paramagnetic Diamond Membrane
The magneto-optic Voigt effect is observed in a synthetic diamond membrane
with a substitutional nitrogen defect concentration in the order of 200 ppm and
a nitrogen-vacancy defect sub-ensemble generated through neutron irradiation
and annealing. The measured polarisation rotation in the reflected light is
observed to be quadratically proportional to the applied magnetic field and to
the incident reflection angle. Additionally, it is observed to be modifiable by
illuminating the diamond with a 532 nm laser. Spectral analysis of the
reflected light under 532 nm illumination shows a slow narrowing of the
spectral distribution, indicating a small increase in the overall
magnetisation, as opposed to magnetisation degradation caused by heating.
Further analysis of the optical power dependence suggest this may be related to
a shift in the spin ensembles charge state equilibrium and, by extension, the
resulting ensemble magnetisation.Comment: 6 pages, 5 figure
Charge stability and charge-state-based spin readout of shallow nitrogen-vacancy centers in diamond
Spin-based applications of the negatively charged nitrogen-vacancy (NV)
center in diamonds require efficient spin readout. One approach is the
spin-to-charge conversion (SCC), relying on mapping the spin states onto the
neutral (NV) and negative (NV) charge states followed by a subsequent
charge readout. With high charge-state stability, SCC enables extended
measurement times, increasing precision and minimizing noise in the readout
compared to the commonly used fluorescence detection. Nano-scale sensing
applications, however, require shallow NV centers within a few \si{\nano
\meter} distance from the surface where surface related effects might degrade
the NV charge state. In this article, we investigate the charge state
initialization and stability of single NV centers implanted \approx
\SI{5}{\nano \meter} below the surface of a flat diamond plate. We demonstrate
the SCC protocol on four shallow NV centers suitable for nano-scale sensing,
obtaining a reduced readout noise of 5--6 times the spin-projection noise
limit. We investigate the general applicability of SCC for shallow NV centers
and observe a correlation between NV charge-state stability and readout noise.
Coating the diamond with glycerol improves both charge initialization and
stability. Our results reveal the influence of the surface-related charge
environment on the NV charge properties and motivate further investigations to
functionalize the diamond surface with glycerol or other materials for
charge-state stabilization and efficient spin-state readout of shallow NV
centers suitable for nano-scale sensing.Comment: 9 pages, 5 figure
Boosting Local Field Enhancement by on-Chip Nanofocusing and Impedance-Matched Plasmonic Antennas
Strongly confined surface plasmon-polariton modes can be used for efficiently
delivering the electromagnetic energy to nano-sized volumes by reducing the
cross sections of propagating modes far beyond the diffraction limit, i.e., by
nanofocusing. This process results in significant local-field enhancement that
can advantageously be exploited in modern optical nanotechnologies, including
signal processing, biochemical sensing, imaging and spectroscopy. Here, we
propose, analyze, and experimentally demonstrate on-chip nanofocusing followed
by impedance-matched nanowire antenna excitation in the end-fire geometry at
telecom wavelengths. Numerical and experimental evidences of the efficient
excitation of dipole and quadrupole (dark) antenna modes are provided,
revealing underlying physical mechanisms and analogies with the operation of
plane-wave Fabry-P\'erot interferometers. The unique combination of efficient
nanofocusing and nanoantenna resonant excitation realized in our experiments
offers a major boost to the field intensity enhancement up to ,
with the enhanced field being evenly distributed over the gap volume of
, and promises thereby a variety of useful
on-chip functionalities within sensing, nonlinear spectroscopy and signal
processing
Cavity-Enhanced Photon Emission from a Single Germanium-Vacancy Center in a Diamond Membrane
The nitrogen-vacancy center in diamond has been explored extensively as a
light-matter interface for quantum information applications, however it is
limited by low coherent photon emission and spectral instability. Here, we
present a promising interface based on an alternate defect with superior
optical properties (the germanium-vacancy) coupled to a finesse
fiber cavity, resulting in a -fold increase
in the spectral density of emission. This work sets the stage for cryogenic
experiments, where we predict a measurable increase in the spontaneous emission
rate.Comment: 7 pages, 6 figure
Integrable systems associated with elliptic algebras
Nitrogen-vacancy (NV) centers in diamonds are interesting due to their
remarkable characteristics that are well suited to applications in
quantum-information processing and magnetic field sensing, as well as
representing stable fluorescent sources. Multiple NV centers in nanodiamonds
(NDs) are especially useful as biological fluorophores due to their chemical
neutrality, brightness and room-temperature photostability. Furthermore, NDs
containing multiple NV centers also have potential in high-precision magnetic
field and temperature sensing. Coupling NV centers to propagating surface
plasmon polariton (SPP) modes gives a base for lab-on-a-chip sensing devices,
allows enhanced fluorescence emission and collection which can further enhance
the precision of NV-based sensors. Here, we investigate coupling of multiple NV
centers in individual NDs to the SPP modes supported by silver surfaces
protected by thin dielectric layers and by gold V-grooves (VGs) produced via
the self-terminated silicon etching. In the first case, we concentrate on
monitoring differences in fluorescence spectra obtained from a source ND, which
is illuminated by a pump laser, and from a scattering ND illuminated only by
the fluorescence-excited SPP radiation. In the second case, we observe changes
in the average NV lifetime when the same ND is characterized outside and inside
a VG. Fluorescence emission from the VG terminations is also observed, which
confirms the NV coupling to the VG-supported SPP modes.Comment: 22 pages, 13 figure