174 research outputs found
Topologically protected elastic waves in one-dimensional phononic crystals of continuous media
We report the design of silica-based 1D phononic crystals (PnCs) with
topologically distinct complete phononic bandgaps (PnBGs) and the observation
of a topologically protected state of elastic waves at their interface. By
choosing different structural parameters of unit cells, two PnCs can possess a
common PnBG with different topological nature. At the interface between the two
PnCs, a topological interface mode with a quality factor of ~5,650 is observed
in the PnBG. Spatial confinement of the interface mode is also confirmed by
using photoelastic imaging technique. Such topologically protected elastic
states are potentially applicable for constructing novel phononic devices.Comment: 23 page
Design of GaAs-based valley phononic crystals with multiple complete phononic bandgaps at ultra-high frequency
We report the design of GaAs-based monolithic valley phononic crystals
(VPnCs) with multiple complete phononic bandgaps, which support simultaneous
valley-protected edge states with different symmetries in the gigahertz (GHz)
range. Rotation of triangular holes in the unit cells breaks the mirror
symmetry, and this orientation degree of freedom enables the structures to
exhibit different valley vortex chiralities. We numerically demonstrate the
transport of multi-band valley-protected edge states with suppressed
backscattering at the sharp corners of the interfaces between different VPnCs.
Such monolithic semiconductor structures pave the way for ultra-high frequency
topological nanophononic applications by using the lithographic technique.Comment: 13 pages, 5 figure
Eigenvalue decomposition method for photon statistics of frequency filtered fields and its applications to quantum dot emitters
A simple calculation method for photon statistics of frequency-filtered
fields is proposed. This method, based on eigenvalue decompositions of
superoperators, allows us to study effects on the photon statistics of spectral
filtering by various types of filters, such as Gaussian and rectangular filters
as well as Lorentzian filters, which is not possible by conventional
approaches. As an example, this method is applied to a simulation of quantum
dot single-photon emitters, where we found the efficient choice of the filter
types to have pure single photons depends on the excitation conditions i.e.
incoherent or coherent (and resonant) excitations.Comment: 9 pages, 5 figure
Scheme for media conversion between electronic spin and photonic orbital angular momentum based on photonic nanocavity
Light with nonzero orbital angular momentum (OAM) or twisted light is
promising for quantum communication applications such as OAM-entangled photonic
qubits. There exist photonic OAM to photonic spin angular momentum (SAM), as
well as photonic SAM to electronic SAM interfaces but not any direct photonic
OAM-electronic SAM (flying to stationary) media converter within a single
device. Here, we propose a scheme which converts photonic OAM to electronic SAM
and vice versa within a single nanophotonic device. We employed a photonic
crystal nanocavity with an embedded quantum dot (QD) which confines an electron
spin as a stationary qubit. Spin polarized emission from the QD drive the
rotation of the nanocavity modes via the strong optical spin-orbit interaction.
The rotating modes then radiate light with nonzero OAM, allowing this device to
serve as a transmitter. As this can be a unitary process, the time-reversed
case enables the device to function as a receiver. This scheme could be
generalized to other systems of resonator and quantum emitters such as a
microdisk and defects in diamond for example. Our scheme shows the potential
for realizing an (ultra)compact electronic SAM-photonic OAM interface to
accommodate OAM as an additional degree of freedom for quantum information
purposes.Comment: 15 pages, 6 figure
Vacuum Rabi spectra of a single quantum emitter
We report the observation of the vacuum Rabi splitting of a single quantum
emitter by measuring its direct spontaneous emission into free space. We used a
semiconductor quantum dot inside a photonic crystal nanocavity, in conjunction
with an appropriate cavity design and filtering with a polarizer and an
aperture, enabling the extraction of the inherently-weak emitter's signal. The
emitter's vacuum Rabi spectra exhibit clear differences to those measured by
detecting the cavity photon leakage. Moreover, we observed an asymmetric vacuum
Rabi spectrum induced by interference between the emitter and cavity detection
channels. Our observations lay the groundwork for accessing various cavity
quantum electrodynamics phenomena that manifest themselves only in the
emitter's direct spontaneous emission.Comment: 12 pages, 9 figure
Transfer-printed single photon sources coupled to wire waveguides
Photonic integrated circuits (PICs) are attractive platforms to perform
large-scale quantum information processing. While highly-functional PICs (e.g.
silicon based photonic-circuits) and high-performance single photon sources
(SPSs, e.g. compound-semiconductor quantum dots (QDs)) have been independently
demonstrated, their combination for single-photon-based applications has still
been limited. This is largely due to the complexities of introducing SPSs into
existing PIC platforms, which are generally realized with different materials
and using distinct fabrication protocols. Here, we report a novel approach to
combine SPSs and PICs prepared independently. We employ transfer printing, by
which multiple desired SPSs can be integrated in a simple pick-and-place manner
with a theoretical waveguide coupling efficiency >99%, fulfilling the demanding
requirements of large-scale quantum applications. Experimentally, we
demonstrated QD-based SPSs with high waveguide coupling efficiencies, together
with the integration of two SPSs into a waveguide. Our approach will accelerate
scalable fusion between modern PICs and cutting-edge quantum technologies.Comment: 16 pages and 5 figures for the main text, 17 pages and 8 figures for
the supplementar
Surface-passivated high-Q GaAs photonic crystal nanocavity with quantum dots
Photonic crystal (PhC) nanocavities with high quality (Q) factors have
attracted much attention because of their strong spatial and temporal light
confinement capability. The resulting enhanced light-matter interactions are
beneficial for diverse photonic applications, ranging from on-chip optical
communications to sensing. However, currently achievable Q factors for active
PhC nanocavities, which embed active emitters inside, are much lower than those
of the passive structures because of large optical loss, presumably originating
from light scattering by structural imperfections and/or optical absorptions.
Here, we demonstrate a significant improvement of Q factors up to ~160,000 in
GaAs active PhC nanocavities using a sulfur-based surface passivation
technique. This value is the highest ever reported for any active PhC
nanocavities with semiconductor quantum dots. The surface-passivated cavities
also exhibit reduced variation in both Q factors and cavity resonant
wavelengths. We find that the improvement in the cavity performance presumably
arises from suppressed light absorption at the surface of the PhC's host
material by performing a set of PL measurements in spectral and time domains.
With the surface passivation technique, we also demonstrate a strongly-coupled
single quantum dot-cavity system based on a PhC nanocavity with a high Q factor
of ~100,000. These results will pave the way for advanced quantum dot-based
cavity quantum electrodynamics and for GaAs micro/nanophotonic applications
containing active emitters
Single plasmon generation in an InAs/GaAs quantum dot in a transfer-printed plasmonic microring resonator
We report single plasmon generation with a self-assembled InAs/GaAs quantum
dot embedded in a plasmonic microring resonator. The plasmonic cavity based on
a GaAs microring is defined on an atomically-smooth silver surface. We
fabricated this structure with the help of transfer printing, which enables the
pick-and-place assembly of the complicated, heterogeneous three dimensional
stack. We show that a high-order surface-plasmon-polariton transverse mode
mediates efficient coupling between the InAs/GaAs quantum dots and the
plasmonic cavity, paving the way for developing plasmonic quantum light sources
based on the state-of-the-art solid-state quantum emitters. Experimentally, we
observed Purcell-enhanced radiation from the quantum dot coupled to the
plasmonic mode. We also observed a strong anti-bunching in the intensity
correlation histogram measured for scattered photons from the plasmonic
resonator, indicating single plasmon generation in the resonator. Our results
will be important in the development of quantum plasmonic circuits integrating
high-performance single plasmon generators.Comment: 6 pages, 4 figures. To appear in ACS photonic
Strongly coupled single quantum dot-cavity system integrated on a CMOS-processed silicon photonic chip
Quantum photonic integrated circuit (QPIC) is a promising tool for
constructing integrated devices for quantum technology applications. In the
optical regime, silicon photonics empowered by
complementary-metal-oxide-semiconductor (CMOS) technology provides optical
components useful for realizing large-scale QPICs. Optical nonlinearity at the
single-photon level is required for QPIC to facilitate photon-photon
interaction. However, to date, realization of optical elements with
deterministic( i.e., not probabilistic) single-photon nonlinearity by using
silicon-based components is challenging, despite the enhancement of the
functionality of QPICs based on silicon photonics. In this study, we realize
for the first time a strongly coupled InAs/GaAs quantum dot-cavity quantum
electrodynamics (QED) system on a CMOS-processed silicon photonic chip. The
heterogeneous integration of the GaAs cavity on the silicon chip is performed
by transfer printing. The cavity QED system on the CMOS photonic chip realized
in this work is a promising candidate for on-chip single-photon nonlinear
element, which constitutes the fundamental component for future applications
based on QPIC, such as, coherent manipulation and nondestructive measurement of
qubit states via a cavity, and efficient single-photon filter and router.Comment: 5 pages, 3 figure
Spin-dependent directional emission from an asymmetry optical waveguide with an embedded quantum dot ensemble
In this study, we examine a photonic wire waveguide embedded with an ensemble
of quantum dots that directionally emits into the waveguide depending on the
spin state of the ensemble. This is accomplished through the aid of the
spin-orbit interaction of light. The waveguide has a two-step stair-like cross
section and embeds quantum dots (QDs) only in the upper step, such that the
circular polarization of emission from the spin-polarized QDs controls the
direction of the radiation. We numerically verify that more than 70% of the
radiation from the ensemble emitter is toward a specific direction in the
waveguide. We also examine a microdisk resonator with a stair-like edge, that
supports selective coupling of the QD ensemble radiation into a whispering
galley mode rotating unidirectionally. Our study provides a foundation for
spin-dependent optoelectronic devices
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