[show abstract][hide abstract] ABSTRACT: We provide a self-consistent electromagnetic theory of the coupling between dipole emitters and dissipative nanoresonators. The theory that relies on the concept of quasinormal modes with complex frequencies provides an accurate closed-form expression for the electromagnetic local density of states of any photonic or plasmonic resonator with strong radiation leakage, absorption, and material dispersion. It represents a powerful tool to calculate and conceptualize the electromagnetic response of systems that are governed by a small number of resonance modes. We use the formalism to revisit Purcell’s factor. The new formula substantially differs from the usual one; in particular, it predicts that a spectral detuning between the emitter and the resonance does not necessarily result in a Lorentzian response in the presence of dissipation. Comparisons with fully vectorial numerical calculations for plasmonic nanoresonators made of gold nanorods evidence the high accuracy of the predictions achieved by our semianalytical treatment.
[show abstract][hide abstract] ABSTRACT: We review the properties of the generation of surface plasmons by
subwavelength isolated slits in metal films and by small ensembles of
slits. After an introduction, in Section 2, we recall the theoretical
modal formalism that allows us to calculate the generation efficiency of
SPP from the total field scattered by an indentation on a metal film. We
also rapidly discuss the main results known of the SPP generation
efficiency by subwavelength tiny slits or grooves. In Section 3, we
consider the special case of wavelength-large slits that support two
propagative modes and that allow us to dynamically control the direction
of generated surface plasmons. In Section 4, we conclude by describing a
compact and efficient device capable of launching SPPs in a single
direction with a normally incident beam.
[show abstract][hide abstract] ABSTRACT: The spontaneous emission of a quantum emitter depends on its
environment. This fundamental effect of quantum electrodynamics has
become a cornerstone of nano-optics, with the objective to control light
absorption and emission at the nanometer scale. At the heart of the
effect lies the emitter-cavity coupling. An important figure of merit is
the famous Q/V ratio introduced by Purcell in 1946 and largely used by
the photonic-crystal community over the last decennia, with Q the
quality factor of the cavity and V the mode volume. Here we revisit the
classical problem of field coupling between quantum emitters and
cavities to encompass the important case of metallic nanoresonators. We
propose a generalized Purcell formula, which substantially differs from
the classical one and which is capable of accurately handling cavity
modes with strong radiative leakage, absorption and material dispersion.
Fully-vectorial numerical calculations obtained for distinct nanocavity
constructs representative of modern studies in nanophotonics provide a
strong support to our theory.
[show abstract][hide abstract] ABSTRACT: We compute the radiative heat transfer between nanostructured gold plates in
the framework of the scattering theory. We predict an enhancement of the heat
transfer as we increase the depth of the corrugations while keeping the
distance of closest approach fixed. We interpret this effect in terms of the
evolution of plasmonic and guided modes as a function of the grating's
Journal of Physics Conference Series 03/2012; 85(18).
[show abstract][hide abstract] ABSTRACT: Through a fully analytical model [Phys. Rev. B 78, 245108 (2008)], we
investigate the impact of several disorder models on backscattering
losses in photonic crystal waveguides. To evaluate their relative
relevance, we compare the predictions with loss measurements. The
comparison suggests that a long-range disorder at the scale of every
hole has to be considered in disorder model, in addition to the more
classical hole surface roughness.
[show abstract][hide abstract] ABSTRACT: The photoluminescence of nitrogen-vacancy (NV) centers in diamond
nanoparticles exhibits specific properties as compared to NV centers in bulk
diamond. For instance large fluctuations of lifetime and brightness from
particle to particle have been reported. It has also been observed that for
nanocrystals much smaller than the mean luminescence wavelength, the particle
size sets a lower threshold for resolution in Stimulated Emission Depletion
(STED) microscopy. We show that all these features can be quantitatively
understood by realizing that the absorption-emission of light by the NV center
is mediated by the diamond nanoparticle which behaves as a dielectric
[show abstract][hide abstract] ABSTRACT: Slow light devices such as photonic crystal waveguides (PhCW) and coupled resonator optical waveguides (CROW) have much promise for optical signal processing applications and a number of successful demonstrations underpinning this promise have already been made. Most of these applications are limited by propagation losses, especially for higher group indices. These losses are caused by technological imperfections ("extrinsic loss") that cause scattering of light from the waveguide mode. The relationship between this loss and the group velocity is complex and until now has not been fully understood. Here, we present a comprehensive explanation of the extrinsic loss mechanisms in PhC waveguides and address some misconceptions surrounding loss and slow light that have arisen in recent years. We develop a theoretical model that accurately describes the loss spectra of PhC waveguides. One of the key insights of the model is that the entire hole contributes coherently to the scattering process, in contrast to previous models that added up the scattering from short sections incoherently. As a result, we have already realised waveguides with significantly lower losses than comparable photonic crystal waveguides as well as achieving propagation losses, in units of loss per unit time (dB/ns) that are even lower than those of state-of-the-art coupled resonator optical waveguides based on silicon photonic wires. The model will enable more advanced designs with further loss reduction within existing technological constraints.
[show abstract][hide abstract] ABSTRACT: A novel metal-coated nanocylinder-cavity architecture fully compatible with III-V GaInAs technology and benefiting from a broad spectral range enhancement of the local density of states is proposed as an integrated source of nonclassical light. Because of a judicious selection of the mode volume, the cavity combines good collection efficiency (≈45%), large Purcell factors (≈15) over a 80 nm spectral range, and a low sensitivity to inevitable spatial mismatches between the single emitter and the cavity mode. This represents a decisive step towards the implementation of reliable solid-state devices for the generation of entangled photon pairs at infrared wavelengths.
[show abstract][hide abstract] ABSTRACT: We report statistical fluctuations for the transmissions of a series of photonic-crystal waveguides (PhCWs) that are supposedly identical and that only differ because of statistical structural fabrication-induced imperfections. For practical PhCW lengths offering tolerable -3dB attenuation with moderate group indices (n(g) approximately 60), the transmission spectra contains very narrow peaks (Q approximately 20,000) that vary from one waveguide to another. The physical origin of the peaks is explained by calculating the actual electromagnetic-field pattern inside the waveguide. The peaks that are observed in an intermediate regime between the ballistic and localization transports are responsible for a smearing of the local density of states, for a rapid broadening of the probability density function of the transmission, and bring a severe constraint on the effective use of slow light for on-chip optical information processing. The experimental results are quantitatively supported by theoretical results obtained with a coupled-Bloch-mode approach that takes into account multiple scattering and localization effects.
[show abstract][hide abstract] ABSTRACT: We report ensemble-average transport characteristics obtained for a series of photonic-crystal waveguides that are supposedly identical and that only differ because of statistical structural fabrication-induced imperfections. In particular, we evidence that, in addition to a smearing of the local density of states, the probability density function of the transmission rapidly broadens in the slow light regime even for group indices as small as ng~20 and for practical situations offering tolerable -3dB losses. This brings a severe constraint on the effective use of slow light for on-chip optical information processing. The experimental results are quantitatively supported by theoretical results obtained with a coupled-Bloch-mode approach that takes into account multiple scattering and localization effects.
[show abstract][hide abstract] ABSTRACT: Different mirror geometries in two-dimensional photonic crystal slabs are studied with fully vectorial calculations. We compare their optical properties and, in particular, we show that, for heterostructure mirrors, the penetration length associated with the delay induced by distributed reflection is not correlated with the characteristic damping length of the electromagnetic energy distribution in the mirror. This unexpected result evidences that the usual trade-off between short damping lengths and large penetration lengths that is classically encountered in distributed Bragg reflectors can be overcome with carefully designed photonic crystal structures.
[show abstract][hide abstract] ABSTRACT: In this Letter, we study slow-light transport in photonic-crystal waveguides in the presence of structural imperfections. In contrast with previous theoretical works that rely on perturbation theories, the present formalism takes into account multiple scattering and localization effects. It allows for a quantitative prediction of the main statistical transport coefficients, including averaged values as well as probability distributions. In particular, we evidence that, as the group velocity decreases, the attenuation probability distribution exhibits a rapid broadening that one should consider for designing slow-light devices.
[show abstract][hide abstract] ABSTRACT: We present a single-photon-source design based on the emission of a quantum dot embedded in a semiconductor (GaAs) nanowire. The nanowire ends are engineered (efficient metallic mirror and tip taper) to reach a predicted record-high collection efficiency of 90% with a realistic design. Preliminary experimental results already show a measured efficiency of 44%.
[show abstract][hide abstract] ABSTRACT: We design several single-photon-sources based on the emission of a quantum dot embedded in a semiconductor (GaAs) nanowire. Through various taper designs, we engineer the nanowire ends to realize efficient metallic-dielectric mirrors and to reduce the divergence of the far-field radiation diagram. Using fully-vectorial calculations and a comprehensive Fabry-Perot model, we show that various realistic nanowire geometries may act as nanoantennas (volume of approximately 0.05 lambda(3)) that assist funnelling the emitted photons into a single monomode channel. Typically, very high extraction efficiencies above 90% are predicted for a collection optics with a numerical aperture NA=0.85. In addition, since no frequency-selective effect is used in our design, this large efficiency is achieved over a remarkably broad spectral range, Deltalambda=70 nm at lambda=950 nm.
[show abstract][hide abstract] ABSTRACT: A fully vectorial Fourier-modal-method approach combined with the Lorentz reciprocity theorem is used to study the capability of isolated subwavelength objects to launch surface plasmon polaritons on a nearby surface under illumination by light. Various 2-D subwavelength geometries, like grooves or ridges, are considered and compared. The highest efficiencies are achieved for metallic ridges isolated from the surface by a dielectric post. We derive general trends with respect to the geometry, the incidence angle, and the frequency of the incident illumination. We additionally discuss particular effects that provide very high efficiencies or unidirectional launchings. The predictions may be useful for further understanding and engineering plasmonic systems formed by nanoparticle ensembles.
IEEE Journal of Selected Topics in Quantum Electronics 01/2009; · 4.08 Impact Factor
[show abstract][hide abstract] ABSTRACT: Using a fully vectorial frequency-domain aperiodic Fourier modal method, we study nanowire metallic mirrors and their photonic performance. We show that the performance of standard quarter-wave Bragg mirrors at subwavelength diameters is surprisingly poor, while engineered metallic mirrors that incorporate a thin dielectric adlayer may offer reflectance larger than 90% even for diameters as small as lambda/5.
[show abstract][hide abstract] ABSTRACT: The quest for enhanced light-matter interactions has enabled a tremendous increase in the performance of photonic-crystal nanoresonators in the past decade. tate-of-the-art nanocavities now offer mode lifetime in the nanosecond range with confinement volumes of a few hundredths of a cubic micrometer. These results are certainly a consequence of the rapid development of fabrication techniques and modeling tools at micro- and nanometric scales. For future applications and developments, it is necessary to deeply understand the intrinsic physical quantities that govern the photon confinement in these cavities. We present a review of the different physical mechanisms at work in the photon confinement of almost all modern PhC cavity constructs. The approach relies on a Fabry-Perot picture and emphasizes three intrinsic quantities, the mirror reflectance, the mirror penetration depth and the defect-mode group velocity, which are often hidden by global analysis relying on an a posteriori analysis of the calculated cavity mode. The discussion also includes nanoresonator constructs, such as the important micropillar cavity, for which some subtle scattering mechanisms significantly alter the Fabry-Perot picture.
[show abstract][hide abstract] ABSTRACT: For the sake of numerical performance, we hybridize two common approaches often used in electromagnetic computations, namely the finite-element method and the aperiodic Fourier modal method. To that end, we propose an extension of the classical S-matrix formalism to numerical situations, which requires handling different mathematical representations of the electromagnetic fields. As shown with a three-dimensional example, the proposed G-matrix formalism is stable and allows for an enhanced performance in terms of numerical accuracy and efficiency.
[show abstract][hide abstract] ABSTRACT: We theoretically study light emission in photonic crystal waveguides and show that remarkably large spontaneous emission rates into the fundamental guided mode (beta-factor > 95%) can be obtained over a 40-nm-large spectral interval at 950 nm.
Lasers and Electro-Optics Society, 2007. LEOS 2007. The 20th Annual Meeting of the IEEE; 11/2007