arXiv subjects

Alessandro Ciattoni

Publications and source records attributed to Alessandro Ciattoni.

At least 19 recordsLinked to original sources

arXiv2026

Far-field spatial coherence driven by lossy objects: first-principles approach unifying scattering of quantum light and thermal emission

Far-field spatial coherence dictates the interference properties of scattered light and thermal emission. Traditionally, these phenomena are treated through disjointed paradigms: classical scattering descriptions assume cold objects lacking quantum fluctuations, idealized quantum scattering schemes ignore dissipation, and semiclassical fluctuational electrodynamics relies on phenomenological noise currents, precluding the consistent treatment of incident quantum states. Here, we develop a first-principles framework based on the modified Langevin noise formalism to unify the scattering of quantum light and the intrinsic thermal emission of finite dissipative objects. We demonstrate that the outgoing far-field spatial coherence separates into an algebraic superposition of two geometry-driven mechanisms, coupled by the global unitarity of the radiation-matter dynamics. The first mechanism, elastic scattering, acts as a non-unitary spatial filter, mode-selectively attenuating and reshaping incident quantum correlations. The second mechanism, thermal emission, originates from localized material dissipation and projects the object's absorption profile into the far field, providing a quantum-vectorial derivation of the macroscopic van Cittert-Zernike theorem. Applying this framework across optical regimes, we determine operational bounds for lossy quantum photonics. Under chaotic thermal illumination, we analytically demonstrate thermal cloaking at equilibrium and show that a passive sink casts a structured thermal shadow geometrically identical to a primary emitter. Under coherent illumination, we derive a thermodynamic phase diagram bounding macroscopic phase correlations, demonstrating that subwavelength nanostructures undergo substantial coherence degradation compared to bulk objects. Finally, under spatially entangled illumination...

quant-ph↗

arXiv2026

Quantum optomechanics of lossy bodies: general approach and structured squeezed vacuum effects

We investigate the overall optomechanical force experienced by a macroscopic lossy object in free space under external quantum illumination. To this end, utilizing the Modified Langevin Noise Formalism (MLNF), we derive the time-averaged expectation value of the Maxwell stress tensor for a non-equilibrium scenario in which the incoming scattering field is prepared in an arbitrary mixed quantum state, while the medium-assisted field is maintained in local thermal equilibrium. In the limit of full radiation-matter thermal equilibrium, our expression exactly recovers the well-known fluctuation-dissipation relation governing the Casimir effect, and, under coherent illumination, it yields the standard classical radiation pressure. We demonstrate that by driving the scattering field with an anisotropic, multimode squeezed vacuum state, the spatial profile of the electromagnetic quantum fluctuations can be engineered to exhibit broken rotational symmetry, thereby inducing a purely quantum mechanical force acting on the object. Such mechanical interaction is generated in the strict absence of a mean field, $\langle\hat{\mathbf{E}}\rangle=0$, and its non-classical nature is evidenced by its reliance on second-order field correlations $\langle\hat{\mathbf{E}}^2\rangle$, unlike classical optical radiation pressure governed by the squared mean field $\langle\hat{\mathbf{E}}\rangle^2$. Applying this exact formulation to a homogeneous lossy sphere, we demonstrate the experimental feasibility of the effect using realistic material parameters and optical estimations. Ultimately, we establish a general formalism for macroscopic quantum optomechanics that operates beyond the constraints of thermal equilibrium, enabling the prediction of regimes where the purely quantum force circumvents classical mean fields and shot noise while preserving the object's macroscopic quantum coherence.

quant-ph↗

arXiv2026

Direct derivation of the modified Langevin noise formalism from the canonical quantization of macroscopic electromagnetism

The modified Langevin noise formalism (MLNF) models the interaction of the quantized electromagnetic field with an arbitrary lossy magneto-dielectric object placed in vacuum using three types of non-interacting bosonic polaritons: scattering, electric, and magnetic. These respectively represent free-space photons scattered by the object, and photons radiated by quantized electric and magnetic dipolar sources embedded within its volume. Recently [A. Ciattoni, Phys. Rev. A 110, 013707 (2024)], this formalism was justified from the canonical quantization of macroscopic electromagnetism (CQME) [Philbin, New J. Phys. 12, 123008 (2010)] in the Heisenberg picture. This was achieved by identifying the polariton operators within the formal solution of the macroscopic Maxwell equations, assuming they obey bosonic commutation relations to retrieve the canonical ones, and showing they diagonalize the CQME Hamiltonian. However, the explicit functional dependence of these polaritons on the underlying canonical field operators remained undetermined. In this paper, we derive the exact analytical expressions for the polariton operators in terms of the canonical CQME field operators. Using these mappings, we provide a direct and rigorous derivation of the MLNF from the canonical theory in the Schr\"odinger picture. Our derivation is structured in three foundational steps: 1) adopting the derived analytical expressions as the constitutive definitions of the polariton operators; 2) mathematically proving that these operators are strictly bosonic as a direct consequence of the canonical commutation relations; and 3) demonstrating that they exactly diagonalize the macroscopic CQME Hamiltonian.

quant-ph↗

arXiv2024

Quantum optical scattering by macroscopic lossy objects: A general approach

We develop a general approach to describe the scattering of quantum light by a lossy macroscopic object placed in vacuum with no restrictions on both its dispersive optical response and its spatially inhomogeneous composition. Our analysis is based on the modified Langevin noise formalism, a recently introduced version of macroscopic quantum electrodynamics where scattering (s) modes are explicitly separated from electric (e) and magnetic (m) medium excitations; accordingly the formalism involves three kinds of non-interacting boson polaritons such that, in the lossless limit, s-polaritons reduce to standard photons whereas e- and m-polaritons disappear. We analytically derive the input-output unitary relation joining the boson operators of the ingoing and outgoing polaritons, a nontrivial result hinging upon original relations which comprehensively describe the transmission-emission-absorption interplay pertaining the classical radiation scattering, relations we here deduce by resorting to the dyadic Green's function properties. Besides we exploit the input-output relation to connect the output state of the field to the input one, this unveiling the role played by various classical electromagnetic dyadics in quantum optical scattering. We specialize the discussion to the most common situation where the object is initially not electromagnetically excited, with the ingoing electromagnetic state only containing s-polaritons, and we analyze the impact of the classical transmission and absorption dyadics on the transitions from ingoing to outgoing s-polariton and on the creation of outgoing e- and m-polaritons, respectively. Since the scattered radiation is collected in the far-field and the object is usually left unmeasured, we analytically derive the reduced density operator of the outgoing s-polaritons.

quant-ph↗

arXiv2024

Quantum electrodynamics of lossy magnetodielectric samples in vacuum: modified Langevin noise formalism

Quantum behavior of the electromagnetic field in unbounded macroscopic media displaying absorption is properly described by the Langevin noise formalism (macroscopic quantum electrodynamics) where the field is assumed to be entirely produced by medium fluctuating sources via the dyadic Green's function. On the other hand, such formalism is able to deal with the case of finite-size lossy objects placed in vacuum only as a limiting situation where the permittivity limit ${\rm Im} ( \varepsilon) \rightarrow 0^+$ pertaining the regions filled by vacuum is taken at the end of the calculations. Strictly setting ${\rm Im} ( \varepsilon) =0$ is forbidden in the Langevin noise formalism since the field would vanish in the lossless regions and this is physically due to the fact that the contribution of the scattering modes to the field is not separated from the contribution produced by the medium fluctuating sources. Recently, a modified Langevin noise formalism has been proposed to encompass the scattering modes and accordingly it is able to describe the structured lossless situations by strictly setting ${\rm Im} (\varepsilon) = 0$. However such modified formalism has been numerically validated only in few specific geometries. In this paper we analytically derive the modified Langevin noise formalism from the established canonical quantization of the electromagnetic field in macroscopic media, thus proving that it models any possible scenario involving linear, inhomegeneous and magnetodielectric samples. The derivation starts from quantum Maxwell equations in the Heisenberg picture together with their formal solution as the superposition of the medium assisted field and the scattering modes. We analytically prove that each of the two field parts can be expressed in term of particular bosonic operators, which in turn diagonalize the electromagnetic Hamiltonian.

quant-ph↗

arXiv2023

XUV plasmonic waveguides by near-zero index heterostructures

The lack of transmissive photonic components in the extreme ultra-violet (XUV) constitutes a challenge for micro/nano-metric confinement. Here, we theoretically design a novel approach to attain XUV radiation guidance based on the electromagnetic properties of Titanium-Aluminum-Titanium heterostructures in such a spectral domain. We show that, thanks to the near-zero-index properties of aluminum and titanium, XUV radiation can couple efficiently with plasma oscillations in such heterostructures, enabling the excitation of several distinct plasmon polariton modes. Our predictions, based on the semi-analytical solution of fully vectorial Maxwell's equations, indicate that the dispersion profile of plasmon polariton modes can get efficiently modulated by the aluminum thickness, enabling nanometre confinement and micrometre propagation length. Moreover, we quantify the third-order nonlinearity enhancement factor, finding that it is resonant at the zero-index wavelength. Our results are promising for the development of future devices enabling advanced control and manipulation of XUV radiation.

physics.optics↗

arXiv2022

Quantum interaction of sub-relativistic aloof electrons with mesoscopic samples

Relativistic electrons experience very slight wave packet distortion and negligible momentum recoil when interacting with nanometer-sized samples, as a consequence of the ultra-short interaction time. Accordingly, modeling fast electrons as classical point-charges provides extremely accurate theoretical predictions of energy-loss spectra. Here we investigate the aloof interaction of nanometer-sized electron beams of few keV with micron-sized samples, a regime where the classical description generally fails due to significant wavefunction broadening and momentum recoil. To cope with these effects, we use macroscopic quantum electrodynamics to analytically derive a generalized expression for the electron energy loss probability which accounts for recoil. Quantum features of the interaction are shown to get dramatically strong as the interaction length is increased and/or the electron kinetic energy is decreased. Moreover, relatively large values of the energy loss probability are found at higher energy losses and larger impact parameters, a marked quantum effect which is classically forbidden by the evanescent profile of the field produced by a moving point-charge.

physics.optics↗

arXiv2022

Fast electrons interacting with chiral matter: mirror symmetry breaking of quantum decoherence and lateral momentum transfer

Photons experience mirror asymmetry of macroscopic chiral media, as in circular dichroism and polarization rotation, since left and right handed circular polarizations differently couple with matter handedness. Conversely, free relativistic electrons with vanishing orbital angular momentum have no handedness so the question arises whether they could sense chirality of geometrically symmetric macroscopic samples. In this Letter, we show that matter chirality breaks mirror symmetry of the scattered electrons quantum decoherence, even when the incident electron wave function and the sample shape have a common reflection symmetry plane. This is physically possible since the wave function transverse smearing triggers electron sensitivity to the spatial asymmetry of the electromagnetic interaction with the sample, as results from our non-perturbative analysis of the scattered electron reduced density matrix, in the framework of macroscopic quantum electrodynamics. Furthermore, we prove that mirror asymmetry also shows up in the distribution of the electron lateral momentum, orthogonal to the geometric symmetry plane, whose non-vanishing mean value reveals that the electron experiences a lateral mechanical interaction entirely produced by matter chirality.

quant-ph↗

arXiv2021

Asymmetric scattering of mirror symmetric radiation from nanostructures coupled to chiral films

The interaction of radiation with chiral molecular films is not macroscopically invariant under mirror reflections and, accordingly, chiroptical effects exist which affect the spatial symmetry of the radiation profile and which nearly exclusively show up in the near-field due to the large molecule-wavelength size mismatch. Here we prove that the scattering of a mirror symmetric pair of plane waves by a nanowire lying on a chiral nanofilm is not mirror symmetric with an angular dissymmetry factor that can be as large as some tenths. Due to evanescent coupling, the nanowire efficiently experiences molecular chirality which produces a spatially asymmetric near-field so that the self-consistent unbalanced excitation of nanowire photonic modes with opposite angular momenta yields asymmetric far-field interference. In addition to enriching the physical understaning of mirror symmetry breaking in chiral nanophotonics, our results could suggest ultra-efficient schemes for enantiomeric discrimination which is essential in biological chemistry and pharmacology.

physics.optics↗

arXiv2021

Mirror optical activity: efficient chiral sensing from electromagnetic parity indefiniteness

Mirror symmetry is among the most fundamental concepts of physics and its spontaneous breaking at the molecular level allows chiral molecules to exist in two enantiomers that are mirror images of each other. The majority of chiro-optical effects routinely used to detect enantiomers in mixtures, as circular dichroism, relies on chiral sensitivity to photon circular polarization, thus not harnessing the full potentials of mirror symmetry breaking which also involves the radiation spatial profile. Here we show that the parity indefiniteness of the electromagnetic field interacting with chiral matter supports mirror optical activity, a novel chiro-optical effect where a chiral film, once probed by the mirror symmetric field of a nanoemitter, produces a near field whose spatial profile has broken mirror symmetry. The detection of near field dissymmetry provides an highly efficient chiral sensing technique, thus opening novel avenues to devising nanonophotonic schemes for ultra-efficient chiral discrimination of picogram quantities of molecules. We specialize the technique to nano-films with infrared chirality by using a swift electron in aloof configuration as the nanoemitter and an off-axis transparent conductor nanoparticle as the near field probe; the spatial dissymmetry factor of nanoparticle cathodoluminescence is one order of magnitude larger than circular dichroism, which is further enhanced to two orders if an additional graphene sheet is deposited on the film interface.

physics.optics↗

arXiv2020

Electric directional steering of cathodoluminescence from graphene-based hydrid nanostructures

Controlling directional emission of nanophotonic radiation sources is fundamental to tailor radiation-matter interaction and to conceive highly efficient nanophotonic devices for on-chip wireless communication and information processing. Nanoantennas coupled to quantum emitters have proven to be very efficient radiation routers, while electrical control of unidirectional emission has been achieved through inelastic tunneling of electrons. Here we prove that the radiation emitted from the interaction of a high-energy electron beam with a graphene-nanoparticle composite has beaming directions which can be made to continuously span the full circle even through small variations of the graphene Fermi energy. Emission directionality stems from the interference between the double cone shaped electron transition radiation and the nanoparticle dipolar diffraction radiation. Tunability is enabled since the interference is ruled by the nanoparticle dipole moment whose amplitude and phase are driven by the hybrid plasmonic resonances of the composite and the absolute phase of the graphene plasmonic polariton launched by the electron, respectively. The flexibility of our method provides a way to exploit graphene plasmon physics to conceive improved nanosources with ultrafast reconfigurable radiation patterns.

physics.optics↗

arXiv2020

Electric control of spin orbit coupling in graphene-based nanostructures with broken rotational symmetry

Spin and angular momenta of light are important degrees of freedom in nanophotonics which control light propagation, optical forces and information encoding. Typically, optical angular momentum is generated using q-plates or spatial light modulators. Here, we show that graphene-supported plasmonic nanostructures with broken rotational symmetry provide a surprising spin to orbital angular momentum conversion, which can be continuously controlled by changing the electrochemical potential of graphene. Upon resonant illumination by a circularly polarized plane wave, a polygonal array of indium-tin-oxide nanoparticles on a graphene sheet generates scattered field carrying electrically-tunable orbital angular momentum. This unique photonic spin-orbit coupling occurs due to the strong coupling of graphene plasmon polaritons and localised surface plasmons of the nanoparticles and leads to the controlled directional excitation of graphene plasmons. The tuneable spin-orbit conversion pave the way to high-rate information encoding in optical communications, electric steering functionalities in optical tweezers, and nanorouting of higher-dimensional entangled photon states.

physics.optics↗

arXiv2019

Broadband optical parametric amplification by two-dimensional semiconductors

Optical parametric amplification is a second-order nonlinear process whereby an optical signal is amplified by a pump via the generation of an idler field. It is the key ingredient of tunable sources of radiation that play an important role in several photonic applications. This mechanism is inherently related to spontaneous parametric down-conversion that currently constitutes the building block for entangled photon pair generation, which has been exploited in modern quantum technologies ranging from computing to communications and cryptography. Here we demonstrate single-pass optical parametric amplification at the ultimate thickness limit; using semiconducting transition-metal dichalcogenides, we show that amplification can be attained over a propagation through a single atomic layer. Such a second-order nonlinear interaction at the 2D limit bypasses phase-matching requirements and achieves ultrabroad amplification bandwidths. The amplification process is independent on the in-plane polarization of the impinging signal and pump fields. First-principle calculations confirm the observed polarization invariance and linear relationship between idler and pump powers. Our results pave the way for the development of atom-sized tunable sources of radiation with applications in nanophotonics and quantum information technology.

physics.optics↗

arXiv2018

Collision quenching in the ultrafast dynamics of plasmonic materials

We explore the nonlinear response of plasmonic materials driven by ultrashort pulses of electromagnetic radiation with temporal duration of few femtoseconds and high peak intensity. By developing the Fokker-Planck-Landau theory of electron collisions, we solve analytically the collisional integral and derive a novel set of hydrodynamical equations accounting for plasma dynamics at ultrashort time scales. While in the limit of small light intensities we recover the well established Drude model of plasmas, in the high intensity limit we observe nonlinear quenching of collision-induced damping leading to absorption saturation. Our results provide a general background to understand electron dynamics in plasmonic materials with promising photonic applications in the manipulation of plasma waves with reduced absorption at the femtosecond time scale.

physics.optics↗

arXiv2018

Diode-like asymmetric transmission in ultrathin hyperbolic epsilon-near-zero slabs: extreme anisotropy mimicking chirality

We demonstrate that a strong asymmetric transmission for forward and backward propagation of tilted circular polarized optical waves is supported by ultrathin epsilon-near-zero hyperbolic slabs. We find that, remarkably, this effect is solely triggered by anisotropy without resorting to any breaking of reciprocity and chiral symmetries or spatial nonlocal effects. In addition, we show that the asymmetric transmission undergoes a dramatic enhancement if the slab is hyperbolic in the epsilon-near-zero regime. This happens since, close to epsilon-near-zero point, the hyperbolic dispersion activates etalon resonances where extraordinary waves accumulate propagation phase even though the slab is ultrathin. The proposed strategy holds promise for realizing ultra-compact and efficient polarization devices at different frequency bands.

physics.optics↗

arXiv2017

Enhanced nonlocal effects in metamaterials with moderate-index inclusions

We investigate a class of multilayered metamaterials characterized by moderate-index inclusions and low average permittivity. Via first-principle calculations, we show that in such scenario first- and second-order spatial dispersion effects may exhibit a dramatic and non-resonant enhancement, and may become comparable to the local response. Their interplay gives access to a wealth of dispersion regimes encompassing additional extraordinary waves and topological phase transitions. In particular, we identify a novel configuration featuring bound and disconnected isofrequency contours. Since they do not rely on high-index inclusions, our proposed metamaterials may constitute an attractive and technologically viable platform for engineering nonlocal effects in the optical range.

physics.optics↗

arXiv2016

Efficient vortex generation in sub-wavelength epsilon-near-zero slabs

We show that a homogeneous and isotropic slab, illuminated by a circularly polarized beam with no topological charge, produces vortices of order two in the opposite circularly polarized components of the reflected and transmitted fields, as a consequence of the difference between transverse magnetic and transverse electric dynamics. In the epsilon-near-zero regime, we find that vortex generation is remarkably efficient in sub-wavelength thick slabs up to the paraxial regime. This physically stems from the fact that a vacuum paraxial field can excite a nonparaxial field inside an epsilon-near-zero slab since it hosts slowly varying fields over physically large portion of the bulk. Our theoretical predictions indicate that epsilon-near-zero media hold great potential as nanophotonic elements for manipulating the angular momentum of the radiation, since they are available without resorting to complicated micro/nano fabrication processes and can operate even at very small (ultraviolet) wavelengths.

physics.optics↗

arXiv2016

Separable metamaterials: analytical ab-initio homogenization and chirality

We investigate the ab-initio homogenization of separable metamaterials with factorized dielectric permittivity profile which can be achieved through suitable grey-scale permittivity design techniques. Separability allows such metamaterials to be physically regarded as the superposition of three fictitious 1D generating media. We prove that, in the long-wavelength limit, separable metamaterials admit simple and analytical description of their electromagnetic bi-anisotropic response which can be reconstructed from the properties of the 1D generating media. Our approach provides a strategy which allows the full ab-initio and flexible design of a complex bianisotropic response by using 1D metamaterials as basic building blocks.

physics.optics↗