19 research outputs found
Inverse design and implementation of a wavelength demultiplexing grating coupler
Nanophotonics has emerged as a powerful tool for manipulating light on chips.
Almost all of today's devices, however, have been designed using slow and
ineffective brute-force search methods, leading in many cases to limited device
performance. In this article, we provide a complete demonstration of our
recently proposed inverse design technique, wherein the user specifies design
constraints in the form of target fields rather than a dielectric constant
profile, and in particular we use this method to demonstrate a new
demultiplexing grating. The novel grating, which has not been developed using
conventional techniques, accepts a vertical-incident Gaussian beam from a
free-space and separates O-band and C-band
light into separate waveguides. This inverse design concept
is simple and extendable to a broad class of highly compact devices including
frequency splitters, mode converters, and spatial mode multiplexers.Comment: 17 pages, 4 figures, 1 table. A supplementary section describing the
inverse-design algorithm in detail has been added, in addition to minor
corrections and updated reference
Single Color Centers Implanted in Diamond Nanostructures
The development of materials processing techniques for optical diamond
nanostructures containing a single color center is an important problem in
quantum science and technology. In this work, we present the combination of ion
implantation and top-down diamond nanofabrication in two scenarios: diamond
nanopillars and diamond nanowires. The first device consists of a 'shallow'
implant (~20nm) to generate Nitrogen-vacancy (NV) color centers near the top
surface of the diamond crystal. Individual NV centers are then isolated
mechanically by dry etching a regular array of nanopillars in the diamond
surface. Photon anti-bunching measurements indicate that a high yield (>10%) of
the devices contain a single NV center. The second device demonstrates 'deep'
(~1\mu m) implantation of individual NV centers into pre-fabricated diamond
nanowire. The high single photon flux of the nanowire geometry, combined with
the low background fluorescence of the ultrapure diamond, allows us to sustain
strong photon anti-bunching even at high pump powers.Comment: 20 pages, 7 figure
Hybrid metal-dielectric nanocavity for enhanced light-matter interactions
Despite tremendous advances in the fundamentals and applications of cavity quantum electrodynamics (CQED), investigations in this field have primarily been limited to optical cavities composed of purely dielectric materials. Here, we demonstrate a hybrid metal-dielectric nanocavity design and realize it in the InAs/GaAs quantum photonics platform utilizing angled rotational metal evaporation. Key features of our nanometallic light-matter interface include: (i) order of magnitude reduction in mode volume compared to that of leading photonic crystal CQED systems; (ii) surface-emitting nanoscale cylindrical geometry and therefore good collection efficiency; and finally (iii) strong and broadband spontaneous emission rate enhancement (Purcell factor textasciitilde 8) of single photons. This light-matter interface may play an important role in quantum technologies
Hybrid Group IV Nanophotonic Structures Incorporating Diamond Silicon-Vacancy Color Centers
We demonstrate a new approach for engineering group IV semiconductor-based
quantum photonic structures containing negatively charged silicon-vacancy
(SiV) color centers in diamond as quantum emitters. Hybrid SiC/diamond
structures are realized by combining the growth of nanoand micro-diamonds on
silicon carbide (3C or 4H polytype) substrates, with the subsequent use of
these diamond crystals as a hard mask for pattern transfer. SiV color
centers are incorporated in diamond during its synthesis from molecular diamond
seeds (diamondoids), with no need for ionimplantation or annealing. We show
that the same growth technique can be used to grow a diamond layer controllably
doped with SiV on top of a high purity bulk diamond, in which we
subsequently fabricate nanopillar arrays containing high quality SiV
centers. Scanning confocal photoluminescence measurements reveal optically
active SiV lines both at room temperature and low temperature (5 K) from
all fabricated structures, and, in particular, very narrow linewidths and small
inhomogeneous broadening of SiV lines from all-diamond nano-pillar arrays,
which is a critical requirement for quantum computation. At low temperatures (5
K) we observe in these structures the signature typical of SiV centers in
bulk diamond, consistent with a double lambda. These results indicate that high
quality color centers can be incorporated into nanophotonic structures
synthetically with properties equivalent to those in bulk diamond, thereby
opening opportunities for applications in classical and quantum information
processing
Enhanced Single Photon Emission from a Diamond-Silver Aperture
We have developed a scalable method for coupling single color centers in
diamond to plasmonic resonators and demonstrated Purcell enhancement of the
single photon emission rate of nitrogen-vacancy (NV) centers. Our structures
consist of single nitrogen-vacancy (NV) center-containing diamond nanoposts
embedded in a thin silver film. We have utilized the strong plasmon resonances
in the diamond-silver apertures to enhance the spontaneous emission of the
enclosed dipole. The devices were realized by a combination of ion implantation
and top-down nanofabrication techniques, which have enabled deterministic
coupling between single NV centers and the plasmonic modes for multiple devices
in parallel. The plasmon-enhanced NV centers exhibited over six-fold
improvements in spontaneous emission rate in comparison to bare nanoposts and
up to a factor of 3.6 in radiative lifetime reduction over bulk samples, with
comparable increases in photon counts. The hybrid diamond-plasmon system
presented here could provide a stable platform for the implementation of
diamond-based quantum information processing and magnetometry schemes.Comment: 16 pages, 4 figure
A Diamond Nanowire Single Photon Antenna
The development of a robust light source that emits one photon at a time is
an outstanding challenge in quantum science and technology. Here, at the
transition from many to single photon optical communication systems, fully
quantum mechanical effects may be utilized to achieve new capabilities, most
notably perfectly secure communication via quantum cryptography. Practical
implementations place stringent requirements on the device properties,
including stable photon generation, room temperature operation, and efficient
extraction of many photons. Single photon light emitting devices based on
fluorescent dye molecules, quantum dots, and carbon nanotube material systems
have all been explored, but none have simultaneously demonstrated all criteria.
Here, we describe the design, fabrication, and characterization of a bright
source of single photons consisting of an individual Nitrogen-vacancy color
center (NV center) in a diamond nanowire operating in ambient conditions. The
nanowire plays a positive role in increasing the number of single photons
collected from the NV center by an order of magnitude over devices based on
bulk diamond crystals, and allows operation at an order of magnitude lower
power levels. This result enables a new class of nanostructured diamond devices
for room temperature photonic and quantum information processing applications,
and will also impact fields as diverse as biological and chemical sensing,
opto-mechanics, and scanning-probe microscopy.Comment: 16 pages, 4 figures, v2: Includes improved reference list; modified
figure 1 to show a large array of NW and FDTD simulation of field profile;
direct experimental comparsion of several bulk/NW devices in figure