Brian Stout - Academia.edu (original) (raw)

Papers by Brian Stout

arXiv (Cornell University), Sep 28, 2018

We use Glauber's correlation function as well as the Green functions formalism to investigate, in... more We use Glauber's correlation function as well as the Green functions formalism to investigate, in the case of a dipolar atomic transition, the causal behaviour of the spontaneously emitted electromagnetic field, in the A.p coupling. This brings us to examine the role played by the longitudinal electric field, which is not described in terms of photonic (transverse) degrees of freedom.

arXiv (Cornell University), Nov 17, 2018

We consider integrals of products of Bessel functions and of spherical Bessel functions, combined... more We consider integrals of products of Bessel functions and of spherical Bessel functions, combined with a Gaussian factor guaranteeing convergence at infinity. Explicit representations are obtained for the integrals, building on those in the 1992 paper by McPhedran, Dawes and Scott. Attention is paid to those sums with a distributive part arising as the Gaussian tends towards a constant. Taking this limit provides explicit analytic formulae for integrals which are difficult to evaluate numerically or otherwise, and whose interpretation has been contentious both in the literature of quantum mechanics and of electromagnetic scattering.

Epj Web of Conferences, Dec 31, 2022

Extensions of the Resonant State or (Quasi-normal mode) formalism are shown to permit unified des... more Extensions of the Resonant State or (Quasi-normal mode) formalism are shown to permit unified descriptions of the true 'bound' states within the framework of the 'leaky' mode formulation of basis sets. We review recent progress in the famed 'normalization/regularization' problems of the QNMs modes as well as the necessity of including 'background' contributions whose expressions can be determined through response function sum-rules.

HAL (Le Centre pour la Communication Scientifique Directe), Nov 29, 2020

International audienc

ACS Photonics, Apr 20, 2016

Understanding how semiconductor quantum dots (QDs) engage in photoinduced energy transfer with ca... more Understanding how semiconductor quantum dots (QDs) engage in photoinduced energy transfer with carbon allotropes is necessary for enhanced performance in solar cells and other optoelectronic devices along with the potential to create new types of (bio)sensors. Here, we systematically investigate energy transfer interactions between C 60 fullerenes and four different QDs, composed of CdSe/ZnS (type I) and CdSe/CdS/ZnS (quasi type II), with emission maxima ranging from 530 to 630 nm. C 60-pyrrolidine tris-acid was first coupled to the N-terminus of a hexahistidineterminated peptide via carbodiimide chemistry to yield a C 60-labeled peptide (pepC 60). This peptide provided the critical means to achieve ratiometric self-assembly of the QD-(pepC 60) nanoheterostructures by exploiting metal affinity coordination to the QD surface. Controlled QD-(pepC 60) N bioconjugates were prepared by discretely increasing the ratio (N) of pepC 60 assembled per QD in mixtures of dimethyl sulfoxide and buffer; this mixed organic/aqueous approach helped alleviate issues of C 60 solubility. An extensive set of control experiments were initially performed to verify the specific and ratiometric nature of QD-(pepC 60) N assembly. Photoinitiated energy transfer in these hybrid organicÀinorganic systems was then interrogated using steady-state and timeresolved fluorescence along with ultrafast transient absorption spectroscopy. Coordination of pepC 60 to the QD results in QD PL quenching that directly tracks with the number of peptides displayed around the QD. A detailed photophysical analysis suggests a competition between electron transfer and Förster resonance energy transfer from the QD to the C 60 that is dependent upon a complex interplay of pepC 60 ratio per QD, the presence of underlying spectral overlap, and contributions from QD size. These results highlight several important factors that must be considered when designing QD-donor/C 60-acceptor systems for potential optoelectronic and biosensing applications.

Journal of the Optical Society of America, Oct 17, 2007

The purpose of this work is to show that an appropriate multiple T-matrix formalism can be useful... more The purpose of this work is to show that an appropriate multiple T-matrix formalism can be useful in performing qualitative studies of the optical properties of colloidal systems composed of nonspherical objects (despite limitations concerning nonspherical particle packing densities). In this work we have calculated the configuration averages of scattering and absorption cross sections of different clusters of dielectric particles. These clusters are characterized by their refraction index, particle shape, and filling fraction. Computations were performed with the recursive centered T-matrix algorithm (RCTMA), a previously established method for solving the multiple scattering equation of light from finite clusters of isotropic dielectric objects. Comparison of the average optical cross sections between the different systems highlights variations in the scattering and absorption properties due to the electromagnetic interactions, and we demonstrate that the magnitudes of these quantities are clearly modulated by the shape of the primary particles.

HAL (Le Centre pour la Communication Scientifique Directe), Jun 17, 2019

International audienc

Physical Review B, Dec 28, 2015

We demonstrate that the electromagnetic fields scattered by metallic particles hosting localized ... more We demonstrate that the electromagnetic fields scattered by metallic particles hosting localized surface plasmons can be accurately reproduced by dielectric particles. We derive analytic formulas relating the permittivities of the dielectric and metallic particles that yield identical dipolar electromagnetic responses. This equivalence between dielectric and metallic particles permits the use of well-known pointlike dipolar models to predict the dipolar resonances of dielectric particles.

Optics Express, Feb 2, 2009

Dielectric microspheres are shown to be capable of confining light in a three-dimensional region ... more Dielectric microspheres are shown to be capable of confining light in a three-dimensional region of subwavelength dimensions when they are illuminated by tightly focused Gaussian beams. We show that a simple configuration, not involving resonances, permits one to reach an effective volume as small as 0.6 (λ/n) 3. It is shown that this threedimensional confinement arises from interferences between the field scattered by the sphere and the high angular components of the incident Gaussian beam passing aside the sphere.

Journal of physics, Mar 1, 2020

Most of the resonant photonic structures behave like open cavities for light where light is trapp... more Most of the resonant photonic structures behave like open cavities for light where light is trapped for some time before leaking or being absorbed. Their modes are called quasi-normal modes and are associated with complex eigenfrequencies ωn = ω n + iω n , ω n characterizing the rate at which the energy leaks from the structure. As a consequence, one can show that the fields of these modes diverge far away from the scatterer. This is problematic when one attempts to develop a theoretical description of the resonant interaction between light and resonant photonic stuctures in terms of their quasi-normal modes. Moreover, the existence or not of a non-resonant term in addition to these resonant contributions is still an open problem. Here, we address these two problems by deriving pole-expansions of the scattering operators of resonant optical structures. We evince the existence of a non-resonant term and we solve the problem of the divergence by studying the scattered field in the time domain and by using the causality principle. The quasi-normal mode expansion that we obtain will be of a great use to study light-matter interactions since it allows to determine the optical response of a photonic resonator both in the time and frequency domain.

arXiv (Cornell University), Feb 3, 2023

arXiv (Cornell University), Mar 17, 2019

Resonant States (RS), also known as Quasi-Normal Modes (QNMs), are eigenstates that arise in spec... more Resonant States (RS), also known as Quasi-Normal Modes (QNMs), are eigenstates that arise in spectral expansions of linear response functions of open systems. Manipulation of these spatially 'divergent' oscillating functions requires a departure from the usual definitions of inner product, normalization and orthogonality typically encountered in the studies of closed systems. We show that once RS fields are expanded on a multipole basis, Gaussian regularization methods provide analytical results for crucial RS inner product integrals in the problematic region exterior to the scattering system. Our demonstrations are carried out in the context of light scattering by spatially bounded objects composed of both electrically and magnetically dispersive media, with demonstrative analytic calculations being shown to completely retrieve the results of exact Mie theory.

arXiv (Cornell University), Apr 6, 2020

Light interaction with optical cavities is of fundamental interest to enhance the light-matter in... more Light interaction with optical cavities is of fundamental interest to enhance the light-matter interaction and to shape the spectral features of the electromagnetic fields. Important efforts have been carried out to develop modal theories of open optical cavities relying on an expansion of the fields on the eigen-fields of the cavity. Here, we show how such an expansion predicts the temporal dynamics of optical resonators. We consider a Fabry-Perot cavity to derive the full analytical expressions of the internal and scattered field on the quasi-normal modes basis together with the complex eigen-frequencies. We evince the convergence and accuracy of this expansion before deriving the impulse response function (IRF) of the open cavity. We benefit from this modal expansion and IRF to demonstrate that the eigen-modes of the open cavity impact the signals only during the transient regimes and not in the permanent regime.

HAL (Le Centre pour la Communication Scientifique Directe), Jul 6, 2015

National audienc

We present a framework for understanding and predicting the different physical properties of nano... more We present a framework for understanding and predicting the different physical properties of nano-antenna using multi-pole theoretical descriptions in terms of S and T matrices. Recent progress in Weierstrass factorization in the context of quasi-normal mode developments has cast new light on their analytical properties and the manner in which they can be used to describe nano-antenna properties.

Laser & Photonics Reviews

The electromagnetic response of optical systems can be described by scattering operators, S, that... more The electromagnetic response of optical systems can be described by scattering operators, S, that link the incoming fields onto the system to the outgoing fields emerging from it. Considerable efforts have been devoted to retrieve the spectral response of the optical systems by expanding the S‐matrix in terms of its singularities. Here a planar optical cavity that allows to derive analytical expressions of poles (in the case of lossless materials) and residues, and reflection/transmission Fresnel coefficients in the harmonic domain is considered. This singularity expansion is used to derive the impulse response function (IRF) of the cavity with respect to the poles of the S‐matrix. The singular expression of the IRF consists of contributions oscillating at the excitation frequency and exponentially decaying contributions that impact signals only during the transient regimes. The convergence of this approach is thoroughly discussed in the case of a dispersive and metallic slab. The c...

EPJ Web of Conferences

The results of experiments performed with a Ø25 x 25 mm solution-grown stilbene crystal in mono-e... more The results of experiments performed with a Ø25 x 25 mm solution-grown stilbene crystal in mono-energetic neutron fields in the 80-to-230 keV energy range are presented. The goal of the measurements, performed at the AMANDE facility, was to explore the capabilities of this organic scintillator to measure neutrons at the lowest possible energy with good pulse shape discrimination (PSD). The time of flight (TOF) technique was used in order to help with the neutron-gamma discrimination. The data are collected via a programmable digital acquisition (DAQ) system CAEN DT7530 using the software CoMPASS with the charge comparison method (CCM). The data are analysed using post-processing codes developed in the ROOT environment. The results show that the stilbene detector has discrimination capabilities for energies as low as 80 keV.

HAL (Le Centre pour la Communication Scientifique Directe), Jul 25, 2016

International audienc

HAL (Le Centre pour la Communication Scientifique Directe), Dec 8, 2020

International audienc

Journal of the Optical Society of America B, 2021

Resonant electromagnetic scattering with particles is a fundamental problem in electromagnetism t... more Resonant electromagnetic scattering with particles is a fundamental problem in electromagnetism that has been thoroughly investigated through the excitation of localized surface plasmon resonances (LSPR) in metallic particles or Mie resonances in high refractive index dielectrics. The interaction strength between electromagnetic waves and scatterers is limited by maximum and minimum physical bounds. Predicting the material composition of a scatterer that will maximize or minimize this interaction is an important objective, but its analytical treatment is challenged by the complexity of the functions appearing in the multipolar Mie theory. Here, we combine different kinds of expansions adapted to the different functions appearing in Mie scattering coefficients to derive simple and accurate expressions of the scattering electric and magnetic Mie coefficients in the form of rational functions. We demonstrate the accuracy of these expressions for metallic and dielectric homogeneous part...

arXiv (Cornell University), Sep 28, 2018

We use Glauber's correlation function as well as the Green functions formalism to investigate, in... more We use Glauber's correlation function as well as the Green functions formalism to investigate, in the case of a dipolar atomic transition, the causal behaviour of the spontaneously emitted electromagnetic field, in the A.p coupling. This brings us to examine the role played by the longitudinal electric field, which is not described in terms of photonic (transverse) degrees of freedom.

arXiv (Cornell University), Nov 17, 2018

We consider integrals of products of Bessel functions and of spherical Bessel functions, combined... more We consider integrals of products of Bessel functions and of spherical Bessel functions, combined with a Gaussian factor guaranteeing convergence at infinity. Explicit representations are obtained for the integrals, building on those in the 1992 paper by McPhedran, Dawes and Scott. Attention is paid to those sums with a distributive part arising as the Gaussian tends towards a constant. Taking this limit provides explicit analytic formulae for integrals which are difficult to evaluate numerically or otherwise, and whose interpretation has been contentious both in the literature of quantum mechanics and of electromagnetic scattering.

Epj Web of Conferences, Dec 31, 2022

Extensions of the Resonant State or (Quasi-normal mode) formalism are shown to permit unified des... more Extensions of the Resonant State or (Quasi-normal mode) formalism are shown to permit unified descriptions of the true 'bound' states within the framework of the 'leaky' mode formulation of basis sets. We review recent progress in the famed 'normalization/regularization' problems of the QNMs modes as well as the necessity of including 'background' contributions whose expressions can be determined through response function sum-rules.

HAL (Le Centre pour la Communication Scientifique Directe), Nov 29, 2020

International audienc

ACS Photonics, Apr 20, 2016

Understanding how semiconductor quantum dots (QDs) engage in photoinduced energy transfer with ca... more Understanding how semiconductor quantum dots (QDs) engage in photoinduced energy transfer with carbon allotropes is necessary for enhanced performance in solar cells and other optoelectronic devices along with the potential to create new types of (bio)sensors. Here, we systematically investigate energy transfer interactions between C 60 fullerenes and four different QDs, composed of CdSe/ZnS (type I) and CdSe/CdS/ZnS (quasi type II), with emission maxima ranging from 530 to 630 nm. C 60-pyrrolidine tris-acid was first coupled to the N-terminus of a hexahistidineterminated peptide via carbodiimide chemistry to yield a C 60-labeled peptide (pepC 60). This peptide provided the critical means to achieve ratiometric self-assembly of the QD-(pepC 60) nanoheterostructures by exploiting metal affinity coordination to the QD surface. Controlled QD-(pepC 60) N bioconjugates were prepared by discretely increasing the ratio (N) of pepC 60 assembled per QD in mixtures of dimethyl sulfoxide and buffer; this mixed organic/aqueous approach helped alleviate issues of C 60 solubility. An extensive set of control experiments were initially performed to verify the specific and ratiometric nature of QD-(pepC 60) N assembly. Photoinitiated energy transfer in these hybrid organicÀinorganic systems was then interrogated using steady-state and timeresolved fluorescence along with ultrafast transient absorption spectroscopy. Coordination of pepC 60 to the QD results in QD PL quenching that directly tracks with the number of peptides displayed around the QD. A detailed photophysical analysis suggests a competition between electron transfer and Förster resonance energy transfer from the QD to the C 60 that is dependent upon a complex interplay of pepC 60 ratio per QD, the presence of underlying spectral overlap, and contributions from QD size. These results highlight several important factors that must be considered when designing QD-donor/C 60-acceptor systems for potential optoelectronic and biosensing applications.

Journal of the Optical Society of America, Oct 17, 2007

The purpose of this work is to show that an appropriate multiple T-matrix formalism can be useful... more The purpose of this work is to show that an appropriate multiple T-matrix formalism can be useful in performing qualitative studies of the optical properties of colloidal systems composed of nonspherical objects (despite limitations concerning nonspherical particle packing densities). In this work we have calculated the configuration averages of scattering and absorption cross sections of different clusters of dielectric particles. These clusters are characterized by their refraction index, particle shape, and filling fraction. Computations were performed with the recursive centered T-matrix algorithm (RCTMA), a previously established method for solving the multiple scattering equation of light from finite clusters of isotropic dielectric objects. Comparison of the average optical cross sections between the different systems highlights variations in the scattering and absorption properties due to the electromagnetic interactions, and we demonstrate that the magnitudes of these quantities are clearly modulated by the shape of the primary particles.

HAL (Le Centre pour la Communication Scientifique Directe), Jun 17, 2019

International audienc

Physical Review B, Dec 28, 2015

We demonstrate that the electromagnetic fields scattered by metallic particles hosting localized ... more We demonstrate that the electromagnetic fields scattered by metallic particles hosting localized surface plasmons can be accurately reproduced by dielectric particles. We derive analytic formulas relating the permittivities of the dielectric and metallic particles that yield identical dipolar electromagnetic responses. This equivalence between dielectric and metallic particles permits the use of well-known pointlike dipolar models to predict the dipolar resonances of dielectric particles.

Optics Express, Feb 2, 2009

Dielectric microspheres are shown to be capable of confining light in a three-dimensional region ... more Dielectric microspheres are shown to be capable of confining light in a three-dimensional region of subwavelength dimensions when they are illuminated by tightly focused Gaussian beams. We show that a simple configuration, not involving resonances, permits one to reach an effective volume as small as 0.6 (λ/n) 3. It is shown that this threedimensional confinement arises from interferences between the field scattered by the sphere and the high angular components of the incident Gaussian beam passing aside the sphere.

Journal of physics, Mar 1, 2020

Most of the resonant photonic structures behave like open cavities for light where light is trapp... more Most of the resonant photonic structures behave like open cavities for light where light is trapped for some time before leaking or being absorbed. Their modes are called quasi-normal modes and are associated with complex eigenfrequencies ωn = ω n + iω n , ω n characterizing the rate at which the energy leaks from the structure. As a consequence, one can show that the fields of these modes diverge far away from the scatterer. This is problematic when one attempts to develop a theoretical description of the resonant interaction between light and resonant photonic stuctures in terms of their quasi-normal modes. Moreover, the existence or not of a non-resonant term in addition to these resonant contributions is still an open problem. Here, we address these two problems by deriving pole-expansions of the scattering operators of resonant optical structures. We evince the existence of a non-resonant term and we solve the problem of the divergence by studying the scattered field in the time domain and by using the causality principle. The quasi-normal mode expansion that we obtain will be of a great use to study light-matter interactions since it allows to determine the optical response of a photonic resonator both in the time and frequency domain.

arXiv (Cornell University), Feb 3, 2023

arXiv (Cornell University), Mar 17, 2019

Resonant States (RS), also known as Quasi-Normal Modes (QNMs), are eigenstates that arise in spec... more Resonant States (RS), also known as Quasi-Normal Modes (QNMs), are eigenstates that arise in spectral expansions of linear response functions of open systems. Manipulation of these spatially 'divergent' oscillating functions requires a departure from the usual definitions of inner product, normalization and orthogonality typically encountered in the studies of closed systems. We show that once RS fields are expanded on a multipole basis, Gaussian regularization methods provide analytical results for crucial RS inner product integrals in the problematic region exterior to the scattering system. Our demonstrations are carried out in the context of light scattering by spatially bounded objects composed of both electrically and magnetically dispersive media, with demonstrative analytic calculations being shown to completely retrieve the results of exact Mie theory.

arXiv (Cornell University), Apr 6, 2020

Light interaction with optical cavities is of fundamental interest to enhance the light-matter in... more Light interaction with optical cavities is of fundamental interest to enhance the light-matter interaction and to shape the spectral features of the electromagnetic fields. Important efforts have been carried out to develop modal theories of open optical cavities relying on an expansion of the fields on the eigen-fields of the cavity. Here, we show how such an expansion predicts the temporal dynamics of optical resonators. We consider a Fabry-Perot cavity to derive the full analytical expressions of the internal and scattered field on the quasi-normal modes basis together with the complex eigen-frequencies. We evince the convergence and accuracy of this expansion before deriving the impulse response function (IRF) of the open cavity. We benefit from this modal expansion and IRF to demonstrate that the eigen-modes of the open cavity impact the signals only during the transient regimes and not in the permanent regime.

HAL (Le Centre pour la Communication Scientifique Directe), Jul 6, 2015

National audienc

We present a framework for understanding and predicting the different physical properties of nano... more We present a framework for understanding and predicting the different physical properties of nano-antenna using multi-pole theoretical descriptions in terms of S and T matrices. Recent progress in Weierstrass factorization in the context of quasi-normal mode developments has cast new light on their analytical properties and the manner in which they can be used to describe nano-antenna properties.

Laser & Photonics Reviews

The electromagnetic response of optical systems can be described by scattering operators, S, that... more The electromagnetic response of optical systems can be described by scattering operators, S, that link the incoming fields onto the system to the outgoing fields emerging from it. Considerable efforts have been devoted to retrieve the spectral response of the optical systems by expanding the S‐matrix in terms of its singularities. Here a planar optical cavity that allows to derive analytical expressions of poles (in the case of lossless materials) and residues, and reflection/transmission Fresnel coefficients in the harmonic domain is considered. This singularity expansion is used to derive the impulse response function (IRF) of the cavity with respect to the poles of the S‐matrix. The singular expression of the IRF consists of contributions oscillating at the excitation frequency and exponentially decaying contributions that impact signals only during the transient regimes. The convergence of this approach is thoroughly discussed in the case of a dispersive and metallic slab. The c...

EPJ Web of Conferences

The results of experiments performed with a Ø25 x 25 mm solution-grown stilbene crystal in mono-e... more The results of experiments performed with a Ø25 x 25 mm solution-grown stilbene crystal in mono-energetic neutron fields in the 80-to-230 keV energy range are presented. The goal of the measurements, performed at the AMANDE facility, was to explore the capabilities of this organic scintillator to measure neutrons at the lowest possible energy with good pulse shape discrimination (PSD). The time of flight (TOF) technique was used in order to help with the neutron-gamma discrimination. The data are collected via a programmable digital acquisition (DAQ) system CAEN DT7530 using the software CoMPASS with the charge comparison method (CCM). The data are analysed using post-processing codes developed in the ROOT environment. The results show that the stilbene detector has discrimination capabilities for energies as low as 80 keV.

HAL (Le Centre pour la Communication Scientifique Directe), Jul 25, 2016

International audienc

HAL (Le Centre pour la Communication Scientifique Directe), Dec 8, 2020

International audienc

Journal of the Optical Society of America B, 2021

Resonant electromagnetic scattering with particles is a fundamental problem in electromagnetism t... more Resonant electromagnetic scattering with particles is a fundamental problem in electromagnetism that has been thoroughly investigated through the excitation of localized surface plasmon resonances (LSPR) in metallic particles or Mie resonances in high refractive index dielectrics. The interaction strength between electromagnetic waves and scatterers is limited by maximum and minimum physical bounds. Predicting the material composition of a scatterer that will maximize or minimize this interaction is an important objective, but its analytical treatment is challenged by the complexity of the functions appearing in the multipolar Mie theory. Here, we combine different kinds of expansions adapted to the different functions appearing in Mie scattering coefficients to derive simple and accurate expressions of the scattering electric and magnetic Mie coefficients in the form of rational functions. We demonstrate the accuracy of these expressions for metallic and dielectric homogeneous part...