pinecone/core-2020-05-10-deduplication huggingface dataset:
Integrated Optical Devices for Lab-on-a-chip Biosensing Applications

The application of portable, easy-to-use and highly sensitive lab-on-a-chip biosensing devices for real-time diagnosis could offer significant advantages over current analytical methods. Integrated optics-based biosensors have become the most suitable technology for lab-on-chip integration due to their ability for miniaturization, their extreme sensitivity, robustness, reliability, and their potential for multiplexing and mass production at low cost. This review provides an extended overview of the state-of-the-art in integrated photonic biosensors technology including interferometers, grating couplers, microring resonators, photonic crystals and other novel nanophotonic transducers. Particular emphasis has been placed on describing their real biosensing applications and wherever possible a comparison of the sensing performances between each type of device is included. The way towards achieving operative lab-on-a-chip platform incorporating the photonic biosensors is also reviewed. Concluding remarks regarding the future prospects and potential impact of this technology are also provided.Funded by: Fundación M. Botín; Spanish Ministry of Industry. Grant Number: SENA project (TSI-020301-2008-11); Spanish Ministry of Science and Innovation. Grant Number: Juan de la Cierva Program (MICINN-JDC).Peer Reviewe
Chiral nanoemitter array: A launchpad for optical vortices

A chiral arrangement of molecular nanoemitters is shown to support delocalised exciton states whose spontaneous decay can generate optical vortex radiation. In contrast to techniques in which phase modification is imposed upon conventional optical beams, this exciton method enables radiation with a helical wave-front to be produced directly. To achieve this end, a number of important polarisation and symmetry-based criteria need to be satisfied. It emerges that the phase structure of the optical field produced by degenerate excitons in a propeller-shaped array can exhibit precisely the sought character of an optical vortex – one with unit topological charge. Practical considerations for the further development of this technique are discussed, and potential new applications are identified
Excitonics of semiconductor quantum dots and wires for lighting and displays

Cataloged from PDF version of article.In the past two decades, semiconductor quantum dots and wires have developed into new, promising classes of materials for next-generation lighting and display systems due to their superior optical properties. In particular, exciton-exciton interactions through nonradiative energy transfer in hybrid systems of these quantum-confined structures have enabled exciting possibilities in light generation. This review focuses on the excitonics of such quantum dot and wire emitters, particularly transfer of the excitons in the complex media of the quantum dots and wires. Mastering excitonic interactions in low-dimensional systems is essential for the development of better light sources, e.g., high-efficiency, high-quality white-light generation; wide-range color tuning; and high-purity color generation. In addition, introducing plasmon coupling provides the ability to amplify emission in specially designed exciton-plasmon nanostructures and also to exceed the Forster limit in excitonic interactions. In this respect, new routes to control excitonic pathways are reviewed in this paper. The review further discusses research opportunities and challenges in the quantum dot and wire excitonics with a future outlook
Chaos-induced transparency in an ultrahigh-Q optical microcavity

We demonstrate experimentally a new form of induced transparency, i.e.,
chaos-induced transparency, in a slightly deformed microcavity which support
both continuous chaotic modes and discrete regular modes with Q factors
exceeding 3X?10^7. When excited by a focused laser beam, the induced
transparency in the transmission spectrum originates from the destructive
interference of two parallel optical pathways: (i) directly refractive
excitation of the chaotic modes, and (ii) excitation of the ultra-high-Q
regular mode via chaos-assisted dynamical tunneling mechanism coupling back to
the chaotic modes. By controlling the focal position of the laser beam, the
induced transparency experiences a highly tunable Fano-like asymmetric
lineshape. The experimental results are modeled by a quantum scattering theory
and show excellent agreement. This chaos-induced transparency is accompanied by
extremely steep normal dispersion, and may open up new possibilities a dramatic
slow light behavior and a significant enhancement of nonlinear interactions.Comment: 5 pages, 5 figue
Multiband processing of multimode light: combining 3D photonic lanterns
  with waveguide Bragg gratings

The first demonstration of narrowband spectral filtering of multimode light
on a 3D integrated photonic chip using photonic lanterns and waveguide Bragg
gratings is reported. The photonic lanterns with multi-notch waveguide Bragg
gratings were fabricated using the femtosecond direct-write technique in
boro-aluminosilicate glass (Corning, Eagle 2000). Transmission dips of up to 5
dB were measured in both photonic lanterns and reference single-mode waveguides
with 10.4-mm-long gratings. The result demonstrates efficient and symmetrical
performance of each of the gratings in the photonic lantern. Such devices will
be beneficial to space-division multiplexed communication systems as well as
for units for astronomical instrumentation for suppression of the atmospheric
telluric emission from OH lines.Comment: 5 pages, 4 figures, accepted to Laser & Photonics Review
Direct high-resolution characterization of quantum correlations via
  classical measurements

Quantum optics plays a central role in the study of fundamental concepts in
quantum mechanics, and in the development of new technological applications.
Typical experiments employ non-classical light, such as entangled photons,
generated by parametric processes. The standard characterization of the sources
by quantum tomography, which relies on detecting the pairs themselves and thus
requires single photon detectors, limits both measurement speed and accuracy.
Here we show that the spectral characterization of the quantum correlations
generated by two-photon sources can be directly performed classically with an
unprecedented spectral resolution. This streamlined technique has the potential
to speed up design and testing of massively parallel integrated sources by
providing a fast and reliable quality control procedure. Adapting our method to
explore other degrees of freedom would allow the complete characterization of
biphoton states generated by parametric processes.Comment: 21 pages, 7 figure
Fiber optical parametric amplifiers in optical communication systems

The prospects for using fiber optical parametric amplifiers (OPAs) in optical communication systems are reviewed. Phase-insensitive amplifiers (PIAs) and phase-sensitive amplifiers (PSAs) are considered. Low-penalty amplification at/or near 1 Tb/s has been achieved, for both wavelength- and time-division multiplexed formats. High-quality mid-span spectral inversion has been demonstrated at 0.64 Tb/s, avoiding electronic dispersion compensation. All-optical amplitude regeneration of amplitude-modulated signals has been performed, while PSAs have been used to demonstrate phase regeneration of phase-modulated signals. A PSA with 1.1-dB noise figure has been demonstrated, and preliminary wavelength-division multiplexing experiments have been performed with PSAs. 512Gb/s have been transmitted over 6,000km by periodic phase conjugation. Simulations indicate that PIAs could reach data rate x reach products in excess of 14,000 Tb/s x km in realistic wavelength-division multiplexed long-haul networks. Technical challenges remaining to be addressed in order for fiber OPAs to become useful for long-haul communication networks are discussed.EC/FP7/224547/EU/Phase sensitive Amplifier Systems and Optical RegeneratorS and their applications/PHASORSEC/FP7/291618/EU/Phase-sensitive optical parametric amplifiers/PSOP
Few-cycle, broadband, mid-infrared optical parametric oscillator pumped by a 20-fs Ti:sapphire laser

A few-cycle, broadband, singly-resonant optical\ud
parametric oscillator (OPO) for the mid-infrared based on MgOdoped\ud
periodically-poled LiNbO3 (MgO:PPLN), synchronously\ud
pumped by a 20-fs Ti:sapphire laser is reported. By using\ud
crystal interaction lengths as short as 250 μm, and careful\ud
dispersion management of input pump pulses and the OPO\ud
resonator, near-transform-limited, few-cycle idler pulses tunable\ud
across the mid-infrared have been generated, with as few\ud
as 3.7 optical cycles at 2682 nm. The OPO can be continuously\ud
tuned over 2179-3732 nm (4589-2680 cm-1) by cavity delay\ud
tuning, providing up to 33 mW of output power at 3723 nm. The\ud
idler spectra exhibit stable broadband profiles with bandwidths\ud
spanning over 422 nm (FWHM) recorded at 3732 nm. The effect\ud
of crystal length on spectral bandwidth and pulse duration is\ud
investigated at a fixed wavelength, confirming near-transformlimited\ud
idler pulses for all grating interaction lengths. By locking\ud
the repetition frequency of the pump laser to a radio-frequency\ud
reference, and without active stabilization of the OPO cavity\ud
length, an idler power stability better than 1.6% rms over >2.75\ud
hours is obtained when operating at maximum output power,\ud
in excellent spatial beam quality with TEM00 mode profile.Peer ReviewedPostprint (published version
Ultra-fast heralded single photon source based on telecom technology

International audienceThe realization of an ultra-fast source of heralded single photons emitted at the wavelength of 1540 nm is reported. The presented strategy is based on state-of-the-art telecom technology, combined with off-the-shelf fiber components and waveguide non-linear stages pumped by a 10 GHz repetition rate laser. The single photons are heralded at a rate as high as 2.1 MHz with a heralding efficiency of 42%. Single photon character of the source is inferred by measuring the second-order autocorrelation function. For the highest heralding rate, a value as low as 0.023 is found. This not only proves negligible multi-photon contributions but also represents the best measured value reported to date for heralding rates in the MHz regime. These prime performances, associated with a device-like configuration, are key ingredients for both fast and secure quantum communication protocols
Unraveling the ultralow threshold stimulated emission from CdZnS/ZnS quantum dot and enabling high-Q microlasers

The newly engineered ternary CdZnS/ZnS colloidal quantum dots (CQDs) are found to exhibit remarkably high photoluminescence quantum yield and excellent optical gain properties. However, the underlying mechanisms, which could offer the guidelines for devising CQDs for optimized photonic devices, remain undisclosed. In this work, through comprehensive steady-state and time-resolved spectroscopy studies on a series of CdZnS-based CQDs, we unambiguously clarify that CdZnS-based CQDs are inherently superior optical gain media in the blue spectral range due to the slow Auger process and that the ultralow threshold stimulated emission is enabled by surface/interface engineering. Furthermore, external cavity-free high-Q quasitoroid microlasers were produced from self-assembly of CdZnS/ZnS CQDs by facile inkjet printing technique. Detailed spectroscopy analysis confirms the whispering gallery mode lasing mechanism of the quasitoroid microlasers. This tempting microlaser fabrication method should be applicable to other solution-processed gain materials, which could trigger broad research interests. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA
Measuring and structuring the spatial coherence length of organic light-emitting diodes

This work was supported by the Engineering and Physical Science Research Council (EPSRC) grants “Challenging the limits of photonics: structured light” EP/J01771X and “Ultra-parallel visible light communications” EP/K00042X. IDWS and KD also acknowledge Royal Society Wolfson Research Merit awards.The spatial coherence of organic light-emitting diodes (OLEDs) is an important parameter that has gained little attention to date. Here we present a method for making quantitative measurements of the spatial coherence of OLEDs using a Young’s double-slit experiment. The usefulness of the method is demonstrated by making measurements on a range of OLEDs with different emitters (iridium and europium complexes) and architectures (bottom- and top-emitting) and the fringe visibility is further manipulated by gratings embedded in external diffractive optical elements. Based on the experiments and simulation of the results, we quantitatively determine the spatial coherence lengths of several OLEDs and find them to be a few micrometers. A 60% increase in the spatial coherence length was observed when using a narrow bandwidth emitter and a metal-coated grating.Publisher PDFPeer reviewe
Normal-dispersion Microcombs Enabled by Controllable Mode Interactions

We demonstrate a scheme incorporating dual coupled microresonators through
which mode interactions are intentionally introduced and controlled for Kerr
frequency comb (microcomb) generation in the normal dispersion region.
Microcomb generation, repetition rate selection, and mode locking are achieved
with coupled silicon nitride microrings controlled via an on-chip microheater.
Our results show for the first time that mode interactions can be programmably
tuned to facilitate broadband normal-dispersion microcombs. The proposed scheme
increases freedom in microresonator design and may make it possible to generate
microcombs in an extended wavelength range (e.g., in the visible) where normal
material dispersion is likely to dominate.Comment: 5 pages, 5 figure
Broadband spin-controlled focusing via logarithmic-spiral nanoslits of varying width

This work presents analytical, numerical and experimental demonstrations of light diffracted through a logarithmic spiral (LS) nanoslit, which forms a type of switchable and focus-tunable structure. Owing to a strong dependence on the incident photon spin, the proposed LS-nanoslit converges incoming light of opposite handedness (to that of the LS-nanoslit) into a confined subwavelength spot, while it shapes light with similar chirality into a donut-like intensity profile. Benefitting from the varying width of the LS-nanoslit, different incident wavelengths interfere constructively at different positions, i.e., the focal length shifts from 7.5 μm (at λ = 632.8 nm) to 10 μm (at λ = 488 nm), which opens up new opportunities for tuning and spatially separating broadband light at the micrometer scale
Deterministic separation of arbitrary photon pair states in integrated
  quantum circuits

Entangled photon pairs generated within integrated devices must often be
spatially separated for their subsequent manipulation in quantum circuits.
Separation that is both deterministic and universal can in principle be
achieved through anti-coalescent two-photon quantum interference. However, such
interference-facilitated pair separation (IFPS) has not been extensively
studied in the integrated setting, where the strong polarization and wavelength
dependencies of integrated couplers -- as opposed to bulk-optics beamsplitters
-- can have important implications for performance beyond the identical-photon
regime. This paper provides a detailed review of IFPS and examines how these
dependencies impact separation fidelity and interference visibility. Focus is
given to IFPS mediated by an integrated directional coupler. The analysis
applies equally to both on-chip and in-fiber implementations, and can be
expanded to other coupler architectures such as multimode interferometers. When
coupler dispersion is present, the separation performance can depend on photon
bandwidth, spectral entanglement, and the linearity of the dispersion. Under
appropriate conditions, reduction in the separation fidelity due to loss of
non-classical interference can be perfectly compensated for by classical
wavelength demultiplexing effects. This work informs the design as well as the
performance assessment of circuits for achieving universal photon pair
separation for states with tunable arbitrary properties.Comment: 11 pages, 14 figures; to be published in Laser & Photonics Review
Spectral engineering of coupled open-access microcavities

Open-access microcavities are emerging as a new approach to confine and
engineer light at mode volumes down to the $\lambda^3$ regime. They offer
direct access to a highly confined electromagnetic field while maintaining
tunability of the system and flexibility for coupling to a range of matter
systems. This article presents a study of coupled cavities, for which the
substrates are produced using Focused Ion Beam milling. Based on experimental
and theoretical investigation the engineering of the coupling between two
microcavities with radius of curvature of \SI{6}{\micro\meter} is demonstrated.
Details are provided by studying the evolution of spectral, spatial and
polarisation properties through the transition from isolated to coupled
cavities. Normal mode splittings up to 20 meV are observed for total mode
volumes around $10 \times \lambda^3$. This work is of importance for future
development of lab-on-a-chip sensors and photonic open-access devices ranging
from polariton systems to quantum simulators.Comment: 6 pages, 2 pages supplementary materials, 6 figure
Giant Gain Enhancement in Surface-Confined Resonant Stimulated Brillouin
  Scattering

The notion that Stimulated Brillouin Scattering (SBS) is primarily defined by
bulk material properties has been overturned by recent work on nanoscale
waveguides. It is now understood that boundary forces of radiation pressure and
electrostriction appearing in such highly confined waveguides can make a
significant contribution to the Brillouin gain. Here, this concept is extended
to show that gain enhancement does not require nanoscale or subwavelength
features, but generally appears where optical and acoustic fields are
simultaneously confined near a free surface or material interface. This
situation routinely occurs in whispering gallery resonators (WGRs), making gain
enhancements much more accessible than previously thought. To illustrate this
concept, the first full-vectorial analytic model for SBS in WGRs is developed,
including optical boundary forces, and the SBS gain in common silica WGR
geometries is computationally evaluated. These results predict that gains
$10^4$ times greater than the predictions of scalar theory may appear in WGRs
even in the 100 um size range. Further, trapezoidal cross-section microdisks
can exhibit very large SBS gains approaching $10^2$ m$^{-1}$W$^{-1}$. With
resonant amplification included, extreme gains on the order of $10^{12}$
m$^{-1}$W$^{-1}$ may be realized, which is $10^8$ times greater than the
highest predicted gains in linear waveguide systems.Comment: 31 pages, 12 figure
Suppression and restoration of disorder-induced light localization mediated by PT-symmetry breaking

We uncover that the breaking point of the PT-symmetry in optical waveguide arrays has a dramatic impact on light localization induced by the off-diagonal disorder. Specifically, when the gain/loss control parameter approaches a critical value at which PT-symmetry breaking occurs, a fast growth of the coupling between neighboring waveguides causes diffraction to dominate to an extent that light localization is strongly suppressed and the statistically averaged width of the output pattern substantially increases. Beyond the symmetry-breaking point localization is gradually restored, although in this regime the power of localized modes grows upon propagation. The strength of localization monotonically increases with disorder at both broken and unbroken PT-symmetry. Our findings are supported by statistical analysis of parameters of stationary eigenmodes of disordered-symmetric waveguide arrays and by analysis of dynamical evolution of single-site excitations in such structures. Parity-time (PT)- symmetric waveguides feature real spectra despite the presence of gain and losses. A spectrum becomes complex at the symmetry-breaking point as the guide characteristics are changed. This paper reports on disorder-induced localization caused by off-diagonal disorder introduced into a PT-symmetric periodic waveguide array. Localization is suppressed near and restored far beyond the symmetry-breaking point. The phenomenon is explained by enhancement of the diffraction in the symmetry-breaking point.Peer ReviewedPostprint (author's final draft
Surface plasmon polariton assisted optical pulling force

We demonstrate both analytically and numerically the existence of optical
pulling forces acting on particles located near plasmonic interfaces. Two main
factors contribute to the appearance of this negative reaction force. The
interference between the incident and reflected waves induces a rotating dipole
with an asymmetric scattering pattern while the directional excitation of
surface plasmon polaritons (SPP) enhances the linear momentum of scattered
light. The strongly asymmetric SPP excitation is determined by spin-orbit
coupling of the rotating dipole and surface plasmon polariton. As a result of
the total momentum conservation, the force acting on the particle points in a
direction opposite to the incident wave propagation. We derive analytical
expressions for the force acting on a dipolar particles placed in the proximity
of plasmonic surfaces. Analytical expressions for this pulling force are
derived within the dipole approximation and are in excellent agreement with
results of electromagnetic numerical calculations. The forces acting on larger
particles are analyzed numerically, beyond the dipole approximation.Comment: 18 pages, 6 figures, supplementary materials (7 pages, movie
Quantum dot materials for terahertz generation applications

Compact and tunable semiconductor terahertz sources providing direct electrical control, efficient operation at room temperatures and device integration opportunities are of great interest at the present time. One of the most well-established techniques for terahertz generation utilises photoconductive antennas driven by ultrafast pulsed or dual-wavelength continuous wave laser systems, though some limitations, such as confined optical wavelength pumping range and thermal breakdown, still exist. The use of quantum dot-based semiconductor materials, having unique carrier dynamics and material properties, can help to overcome limitations and enable efficient optical-to-terahertz signal conversion at room temperatures. Here we discuss the construction of novel and versatile terahertz transceiver systems based on quantum dot semiconductor devices. Configurable, energy-dependent optical and electronic characteristics of quantum-dot-based semiconductors are described, and the resonant response to optical pump wavelength is revealed. Terahertz signal generation and detection at energies that resonantly excite only the implanted quantum dots opens the potential for using compact quantum dot-based semiconductor lasers as pump sources. Proof-of-concept experiments are demonstrated here that show quantum dot-based samples to have higher optical pump damage thresholds and reduced carrier lifetime with increasing pump power