21 research outputs found
Enhancement of bulk second-harmonic generation from silicon nitride films by material composition
We present a comprehensive tensorial characterization of second-harmonic
generation from silicon nitride films with varying composition. The samples
were fabricated using plasma-enhanced chemical vapor deposition, and the
material composition was varied by the reactive gas mixture in the process. We
found a six-fold enhancement between the lowest and highest second-order
susceptibility, with the highest value of approximately 5 pm/V from the most
silicon-rich sample. Moreover, the optical losses were found to be sufficiently
small (below 6 dB/cm) for applications. The tensorial results show that all
samples retain in-plane isotropy independent of silicon content, highlighting
the controllability of the fabrication process.Comment: 4 pages, 3 figures, 2 tables; Re-submitted to Optics Letter
Nanoscale sensing based on nitrogen vacancy centers in single crystal diamond and nanodiamonds : achievements and challenges
Powered by the mutual developments in instrumentation, materials and theoretical descriptions,
sensing and imaging capabilities of quantum emitters in solids have significantly increased in the past
two decades. Quantum emitters in solids, whose properties resemble those of atoms and ions, provide
alternative ways to probing natural and artificial nanoscopic systems with minimum disturbance and
ultimate spatial resolution. Among those emerging quantum emitters, the nitrogen vacancy (NV)
color center in diamond is an outstanding example due to its intrinsic properties at room temperature
(highly-luminescent, photo-stable, biocompatible, highly-coherent spin states). This review article
summarizes recent advances and achievements in using NV centers within nano- and single crystal
diamonds in sensing and imaging. We also highlight prevalent challenges and material aspects for
different types of diamond and outline the main parameters to consider when using color centers as
sensors. As a novel sensing resource, we highlight the properties of NV centers as light emitting
electrical dipoles and their coupling to other nanoscale dipoles e.g. graphene
Surface-induced charge state conversion of nitrogen-vacancy defects in nanodiamonds
We present a study of the charge state conversion of single nitrogen-vacancy
(NV) defects hosted in nanodiamonds (NDs). We first show that the proportion of
negatively-charged NV defects, with respect to its neutral counterpart
NV, decreases with the size of the ND. We then propose a simple model
based on a layer of electron traps located at the ND surface which is in good
agreement with the recorded statistics. By using thermal oxidation to remove
the shell of amorphous carbon around the NDs, we demonstrate a significant
increase of the proportion of NV defects in 10-nm NDs. These results are
invaluable for further understanding, control and use of the unique properties
of negatively-charged NV defects in diamondComment: 6 pages, 4 figure
Cascaded four-wave mixing in tapered plasmonic nanoantenna
We study theoretically the cascaded four-wave mixing (FWM) in broadband
tapered plasmonic nanoantennas and demonstrate a 300-fold increase in nonlinear
frequency conversion detected in the main lobe of the nanoantenna far-field
pattern. This is achieved by tuning the elements of the nanoantenna to resonate
frequencies involved into the FWM interaction. Our findings have a potentially
broad application in ultrafast nonlinear spectroscopy, sensing, on-chip optical
frequency conversion, nonlinear optical metamaterials and photon sources
Near‐Field Energy Transfer between a Luminescent 2D Material and Color Centers in Diamond
Energy transfer between fluorescent probes lies at the heart of many
applications ranging from bio-sensing and -imaging to enhanced photo-detection
and light harvesting. In this work, we study F\"orster resonance energy
transfer (FRET) between shallow defects in diamond --- nitrogen-vacancy (NV)
centers --- and atomically-thin, two-dimensional materials --- tungsten
diselenide (WSe). By means of fluorescence lifetime imaging, we demonstrate
the occurrence of FRET in the WSe/NV system. Further, we show that in the
coupled system, NV centers provide an additional excitation pathway for WSe
photoluminescence. Our results constitute the first step towards the
realization of hybrid quantum systems involving single-crystal diamond and
two-dimensional materials that may lead to new strategies for studying and
controlling spin transfer phenomena and spin valley physics
Second-harmonic generation from coupled plasmon modes in a single dimer of gold nanospheres
We show that a dimer made of two gold nanospheres exhibits a remarkable
efficiency for second-harmonic generation under femtosecond optical excitation.
The detectable nonlinear emission for the given particle size and excitation
wavelength arises when the two nanoparticles are as close as possible to
contact, as in situ controlled and measured using the tip of an atomic force
microscope. The excitation wavelength dependence of the second-harmonic signal
supports a coupled plasmon resonance origin with radiation from the dimer gap.
This nanometer-size light source might be used for high-resolution near-field
optical microscopy.Comment: 6 pages, 5 figure