Hyper-Rayleigh scattering in centrosymmetric systems
TL;DR: The detailed derivation in this work leads to results which are summarized for perpendicular detection of polarization components both parallel and perpendicular to the pump radiation, leading to distinct polarization ratio results, as well as a reversal ratio for forward scattered circular polarizations.
Abstract: Hyper-Rayleigh scattering (HRS) is an incoherent mechanism for optical second harmonic generation. The frequency-doubled light that emerges from this mechanism is not emitted in a laser-like manner, in the forward direction; it is scattered in all directions. The underlying theory for this effect involves terms that are quadratic in the incident field and involves an even-order optical susceptibility (for a molecule, its associated hyperpolarizability). In consequence, HRS is often regarded as formally forbidden in centrosymmetric media. However, for the fundamental three-photon interaction, theory based on the standard electric dipole approximation, representable as E13, does not account for all experimental observations. The relevant results emerge upon extending the theory to include E12M1 and E12E2 contributions, incorporating one magnetic dipolar or electric quadrupolar interaction, respectively, to a consistent level of multipolar expansion. Both additional interactions require the deployment of higher orders in the multipole expansion, with the E12E2 interaction analogous in rank and parity to a four-wave susceptibility. To elicit the correct form of response from fluid or disordered media invites a tensor representation which does not oversimplify the molecular components, yet which can produce results to facilitate the interpretation of experimental observations. The detailed derivation in this work leads to results which are summarized for the following: perpendicular detection of polarization components both parallel and perpendicular to the pump radiation, leading to distinct polarization ratio results, as well as a reversal ratio for forward scattered circular polarizations. The results provide a route to handling data with direct physical interpretation, to enable the more sophisticated design of molecules with sought nonlinear optical properties.
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TL;DR: In this article, a broad guide to cutting-edge applications of quantum electrodynamics is provided, providing an outline of its underlying foundation and an examination of its role in photon science.
Abstract: One of the key frameworks for developing the theory of light–matter interactions in modern optics and photonics is quantum electrodynamics (QED). Contrasting with semiclassical theory, which depicts electromagnetic radiation as a classical wave, QED representations of quantized light fully embrace the concept of the photon. This tutorial review is a broad guide to cutting-edge applications of QED, providing an outline of its underlying foundation and an examination of its role in photon science. Alongside the full quantum methods, it is shown how significant distinctions can be drawn when compared to semiclassical approaches. Clear advantages in outcome arise in the predictive capacity and physical insights afforded by QED methods, which favors its adoption over other formulations of radiation–matter interaction.
36 citations
TL;DR: In the wide realm of applications of quantum electrodynamics, a non-covariant formulation of theory is particularly well suited to describing the interactions of light with molecular matter, and a variety of symmetry principles are drawn out with reference to applications.
Abstract: In the wide realm of applications of quantum electrodynamics, a non-covariant formulation of theory is particularly well suited to describing the interactions of light with molecular matter The robust framework upon which this formulation is built, fully accounting for the intrinsically quantum nature of both light and the molecular states, enables powerful symmetry principles to be applied With their origins in the fundamental transformation properties of the electromagnetic field, the application of these principles can readily resolve issues concerning the validity of mechanisms, as well as facilitate the identification of conditions for widely ranging forms of linear and nonlinear optics Considerations of temporal, structural, and tensorial symmetry offer significant additional advantages in correctly registering chiral forms of interaction More generally, the implementation of symmetry principles can considerably simplify analysis by reducing the number of independent quantities necessary to relate to experimental results to a minimum In this account, a variety of such principles are drawn out with reference to applications, including recent advances Connections are established with parity, duality, angular momentum, continuity equations, conservation laws, chirality, and spectroscopic selection rules Particular attention is paid to the optical interactions of molecules as they are commonly studied, in fluids and randomly organised media
18 citations
Cites background from "Hyper-Rayleigh scattering in centro..."
...The associated ‘J’ and ‘K’ tensors molecular tensors retain index permutational symmetry if the M1 or E2 interaction is involved in the output emission, but not if it is linked with one of the two input photon annihilation events [80,81]....
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TL;DR: This work presents a rigorous quantum electrodynamical analysis of the scattering process, involving a partially index-symmetric construction of the fourth-rank γ tensor-dispensing with the Kleinman symmetry condition.
Abstract: Third-harmonic scattering is a nonlinear optical process that involves the molecular second-hyperpolarizability, γ. This work presents a rigorous quantum electrodynamical analysis of the scattering process, involving a partially index-symmetric construction of the fourth-rank γ tensor—dispensing with the Kleinman symmetry condition. To account for stochastic molecular rotation in fluids, methods of isotropic averaging must be employed to relate the molecular properties to accessible experimental quantities such as depolarization ratio. A complete eighth-rank tensor rotational average yields results for observable third-harmonic scattering rates, cast as a function of the natural-invariant γ components, and the polarization geometry of the experiment. Decomposing the tensor γ into irreducible weights allows specific predictions to be made for each molecular point group, allowing greater discrimination between the results for different molecular symmetries.
15 citations
TL;DR: In this paper, six water-soluble bications, characterized by a symmetric A+-π-D-π+A+ structure, were synthesized and comprehensively studied for their absorption and fluorescence properties, and their nonlinear optical response.
12 citations
TL;DR: In this article, a detailed quantum electrodynamical analysis highlights a mechanism exhibiting the possibility of a delocalized origin for paired output photons: the spatial extent of the region from which the pair is generated can be much larger than previously thought.
Abstract: The generation of correlated photon pairs is a key to the production of entangled quantum states, which have a variety of applications within the area of quantum information. In spontaneous parametric down-conversion—the primary method of generating correlated photon pairs—the associated photon annihilation and creation events are generally thought of as being colocated: The correlated pair of photons is localized with regards to the pump photon and its positional origin. A detailed quantum electrodynamical analysis highlights a mechanism exhibiting the possibility of a delocalized origin for paired output photons: The spatial extent of the region from which the pair is generated can be much larger than previously thought. The theory of both localized and nonlocalized degenerate down-conversion is presented, followed by a quantitative analysis using discrete-volume computational methods. The results may have significant implications for quantum information and imaging applications, and the design of nonlinear optical metamaterials.
6 citations
Cites background from "Hyper-Rayleigh scattering in centro..."
...Higher-order couplings that occur outside the electric-dipole approximation become significant when studying chiral discriminatory effects in optical processes including forces [70] and nonlinear optics [71,72]....
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References
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TL;DR: A theory of hyper−Raman scattering by optically active molecules is presented in this article, where it is shown that scattering intensities depend on the helicity of the incident light.
Abstract: A theory of hyper−Raman scattering by optically active molecules is presented. It is shown that scattering intensities depend on the helicity of the incident light: Expressions for the differential scattering intensities are derived taking into account electric dipole and quadrupole and magnetic dipole interactions. A helical box model is used to estimate circular differential scattering intensity ratios and depolarization ratios.
37 citations
TL;DR: In this article, the magnetic-dipole and electric-quadrupole contributions to second-harmonic generation (SHG) of centro-symmetric media were studied.
Abstract: We have studied the magnetic-dipole and electric-quadrupole contributions to second-harmonic generation (SHG) of centro-symmetric media. It can be shown that the phenomenological parameters α, β, γ can be arranged to form an effective\(\bar \chi _s^{(2)} \)-tensor, which describes dipole-forbidden SHG as the effect of a surface layer upon excitation with a single plane electromagnetic wave. An experimental technique is proposed allowing a determination of the usually very small γ term due to magnetic-dipole interaction using coherent compensation of its contribution by a coverage with an appropriate dye monolayer.
36 citations
TL;DR: In this paper, polarization-resolved hyper-Rayleigh scattering experiments are performed for mixed suspensions of a constant concentration of 4-(4-dihexadecylaminostyryl)-N-methylpyridinium iodide (DiA), a cationic amphiphilic compound with a strong quadratic hyperpolarizability, and varying concentrations of sodium dodecyl sulfate (SDS), an anionic surfactant with a vanishing quad ratic hyper polarizationizability.
Abstract: Polarization-resolved hyper-Rayleigh scattering experiments are reported for mixed suspensions of a constant concentration of 4-(4-dihexadecylaminostyryl)-N-methylpyridinium iodide (DiA), a cationic amphiphilic compound with a strong quadratic hyperpolarizability, and varying concentrations of sodium dodecyl sulfate (SDS), an anionic surfactant with a vanishing quadratic hyperpolarizability. It is observed that the electric dipole contribution of the HRS signal intensity attributed to the free DiA molecules in the solution decreases with an increasing concentration of SDS whereas the electric quadrupole contribution increases simultaneously. These changes are direct indicators of the molecular changes undergone in the solution, and in particular the appearance of centrosymmetric mixed DiA-SDS micelles. A detailed analysis of the HRS signal intensity is performed, allowing the monitoring of the evolution of the organization of these mixed molecular systems. These experimental results are described within a...
34 citations
TL;DR: The first explicit expressions for the rotational average of five-, six-, and seven-photon absorption cross sections are derived, which are one of the required steps in making the calculation of these higher-order absorption properties possible.
Abstract: Rotational averaging of tensors is a crucial step in the calculation of molecular properties in isotropic media. We present a scheme for the rotational averaging of multiphoton absorption cross sections. We extend existing literature on rotational averaging to even-rank tensors of arbitrary order and derive equations that require only the number of photons as input. In particular, we derive the first explicit expressions for the rotational average of five-, six-, and seven-photon absorption cross sections. This work is one of the required steps in making the calculation of these higher-order absorption properties possible. The results can be applied to any even-rank tensor provided linearly polarized light is used.
31 citations
TL;DR: In this paper, a molecular theory of harmonic generation in free molecules is developed using the principles of quantum electrodynamics, and emphasis is placed on the rotational average which is required to account for the random molecular orientations in the pump beam.
Abstract: A molecular theory of harmonic generation in free molecules is developed using the principles of quantum electrodynamics. A Cartesian tensor formalism is employed and emphasis is placed on the rotational average which is required to account for the random molecular orientations in the pump beam. It is demonstrated that even harmonics are forbidden to all orders of the multipolar interaction Hamiltonian and in the appendix a new relation involving the rotational average of an arbitrary rank Cartesian tensor is presented.
29 citations