33 research outputs found
Coulomb and quenching effects in small nanoparticle-based spasers
We study numerically the effect of mode mixing and direct dipole-dipole
interactions between gain molecules on spasing in a small composite
nanoparticles with a metallic core and a dye-doped dielectric shell. By
combining Maxwell-Bloch equations with Green's function formalism, we calculate
lasing frequency and threshold population inversion for various gain densities
in the shell. We find that gain coupling to nonresonant plasmon modes has a
negligible effect on spasing threshold. In contrast, the direct dipole-dipole
coupling, by causing random shifts of gain molecules' excitation frequencies,
hinders reaching the spasing threshold in small systems. We identify a region
of parameter space in which spasing can occur considering these effects.Comment: 7 pages, 6 figure
Toroidal qubits: naturally-decoupled quiet artificial atoms
The requirements of quantum computations impose high demands on the level of
qubit protection from perturbations; in particular, from those produced by the
environment. Here we propose a superconducting flux qubit design that is
naturally protected from ambient noise. This decoupling is due to the qubit
interacting with the electromagnetic field only through its toroidal moment,
which provides an unusual qubit-field interaction
Optical computing by injection-locked lasers
A programmable optical computer has remained an elusive concept. To construct
a practical computing primitive equivalent to an electronic Boolean logic, one
should find a nonlinear phenomenon that overcomes weaknesses present in many
optical processing schemes. Ideally, the nonlinearity should provide a
functionally complete set of logic operations, enable ultrafast all-optical
programmability, and allow cascaded operations without a change in the
operating wavelength or in the signal encoding format. Here we demonstrate a
programmable logic gate using an injection-locked Vertical-Cavity
Surface-Emitting Laser (VCSEL). The gate program is switched between the AND
and the OR operations at the rate of 1 GHz with Bit Error Ratio (BER) of 10e-6
without changes in the wavelength or in the signal encoding format. The scheme
is based on nonlinearity of normalization operations, which can be used to
construct any continuous complex function or operation, Boolean or otherwise.Comment: 47 pages, 7 figures in total, 2 tables. Intended for submission to
Nature Physics within the next two week
Data transmission in long-range dielectric-loaded surface plasmon polariton waveguides
In this paper we report successful transmission of 10 Gbit/s on-off-keying
(OOK) modulated signal through the LR-DLSPPWs with almost negligible
degradation of the data flow consistenc
Toroidal qubits: naturally-decoupled quiet artificial atoms
The requirements of quantum computations impose high demands on the level of qubit protection from perturbations; in particular, from those produced by the environment. Here we propose a superconducting flux qubit design that is naturally protected from ambient noise. This decoupling is due to the qubit interacting with the electromagnetic field only through its toroidal moment, which provides an unusual qubit-field interaction, which is suppressed at low frequencies
A simple and versatile analytical approach for planar metamaterials
We present an analytical model which permits the calculation of effective
material parameters for planar metamaterials consisting of arbitrary unit cells
(metaatoms) formed by a set of straight wire sections of potentially different
shape. The model takes advantage of resonant electric dipole oscillations in
the wires and their mutual coupling. The pertinent form of the metaatom
determines the actual coupling features. This procedure represents a kind of
building block model for quite different metaatoms. Based on the parameters
describing the individual dipole oscillations and their mutual coupling the
entire effective metamaterial tensor can be determined. By knowing these
parameters for a certain metaatom it can be systematically modified to create
the desired features. Performing such modifications effective material
properties as well as the far field intensities remain predictable. As an
example the model is applied to reveal the occurrence of optical activity if
the split ring resonator metaatom is modified to L- or S-shaped metaatoms.Comment: 5 figures, 1 tabl
Nonradiating anapole modes in dielectric nanoparticles
Nonradiating current configurations attract attention of physicists for many years as possible models of stable atoms. One intriguing example of such a nonradiating source is known as 'anapole'. An anapole mode can be viewed as a composition of electric and toroidal dipole moments, resulting in destructive interference of the radiation fields due to similarity of their far-field scattering patterns. Here we demonstrate experimentally that dielectric nanoparticles can exhibit a radiationless anapole mode in visible. We achieve the spectral overlap of the toroidal and electric dipole modes through a geometry tuning, and observe a highly pronounced dip in the far-field scattering accompanied by the specific near-field distribution associated with the anapole mode. The anapole physics provides a unique playground for the study of electromagnetic properties of nontrivial excitations of complex fields, reciprocity violation and Aharonov-Bohm like phenomena at optical frequencies.The work of A.E.M. was supported by the Australian Research Council via Future
Fellowship program (FT110100037). The authors at DSI were supported by DSI core
funds. Fabrication, Scanning Electron Microscope Imaging and NSOM works were
carried out in facilities provided by SnFPC@DSI (SERC Grant 092 160 0139). Zhen Ying
Pan (DSI) is acknowledged for SEM imaging. Yi Zhou (DSI) is acknowledged for silicon
film growth. Leonard Gonzaga (DSI), Yeow Teck Toh (DSI) and Doris Ng (DSI) are
acknowledged for development of the silicon nanofabrication procedure. B.N.C.
acknowledges support from the Government of Russian Federation, Megagrant No.
14.B25.31.0019
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High-bit rate ultra-compact light routing with mode-selective on-chip nanoantennas
Optical nanoantennas provide a promising pathway toward advanced manipulation of light waves, such as directional scattering, polarization conversion, and fluorescence enhancement. Although these functionalities were mainly studied for nanoantennas in free space or on homogeneous substrates, their integration with optical waveguides offers an important âwiredâ connection to other functional optical components. Taking advantage of the nanoantennaâs versatility and unrivaled compactness, their imprinting onto optical waveguides would enable a marked enhancement of design freedom and integration density for optical on-chip devices. Several examples of this concept have been demonstrated recently. However, the important question of whether nanoantennas can fulfill functionalities for high-bit rate signal transmission without degradation, which is the core purpose of many integrated optical applications, has not yet been experimentally investigated. We introduce and investigate directional, polarization-selective, and mode-selective on-chip nanoantennas integrated with a silicon rib waveguide. We demonstrate that these nanoantennas can separate optical signals with different polarizations by coupling the different polarizations of light vertically to different waveguide modes propagating into opposite directions. As the central result of this work, we show the suitability of this concept for the control of optical signals with ASK (amplitude-shift keying) NRZ (nonreturn to zero) modulation [10 Gigabit/s (Gb/s)] without significant bit error rate impairments. Our results demonstrate that waveguide-integrated nanoantennas have the potential to be used as ultra-compact polarization-demultiplexing on-chip devices for highâbit rate telecommunication applications
All-optical majority gate based on an injection-locked laser
An all-optical computer has remained an elusive concept. To construct a practical computing primitive equivalent to an electronic Boolean logic, one should utilize nonlinearity that overcomes weaknesses that plague many optical processing schemes. An advantageous nonlinearity provides a complete set of logic operations and allows cascaded operations without changes in wavelength or in signal encoding format. Here we demonstrate an all-optical majority gate based on a vertical-cavity surface-emitting laser (VCSEL). Using emulated signal coupling, the arrangement provides Bit Error Ratio (BER) of 10(-6) at the rate of 1 GHz without changes in the wavelength or in the signal encoding format. Cascaded operation of the injection-locked laser majority gate is simulated on a full adder and a 3-bit ripple-carry adder circuits. Finally, utilizing the spin-flip model semiconductor laser rate equations, we prove that injection-locked lasers may perform normalization operations in the steady-state with an arbitrary linear state of polarization.Peer reviewe
All-optical majority gate based on an injection-locked laser
An all-optical computer has remained an elusive concept. To construct a practical computing primitive equivalent to an electronic Boolean logic, one should utilize nonlinearity that overcomes weaknesses that plague many optical processing schemes. An advantageous nonlinearity provides a complete set of logic operations and allows cascaded operations without changes in wavelength or in signal encoding format. Here we demonstrate an all-optical majority gate based on a vertical-cavity surface-emitting laser (VCSEL). Using emulated signal coupling, the arrangement provides Bit Error Ratio (BER) of 10â»â¶ at the rate of 1 GHz without changes in the wavelength or in the signal encoding format. Cascaded operation of the injection-locked laser majority gate is simulated on a full adder and a 3-bit ripple-carry adder circuits. Finally, utilizing the spin-flip model semiconductor laser rate equations, we prove that injection-locked lasers may perform normalization operations in the steady-state with an arbitrary linear state of polarization