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Journal ArticleDOI

Hyper-Rayleigh scattering in centrosymmetric systems

28 Sep 2015-Journal of Chemical Physics (AIP Publishing)-Vol. 143, Iss: 12, pp 124301-124301
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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Citations
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Journal ArticleDOI
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

Journal ArticleDOI
23 Jul 2018-Symmetry
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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Journal ArticleDOI
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

Journal ArticleDOI
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

Journal ArticleDOI
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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Journal ArticleDOI
TL;DR: In this paper, the combination of two design strategies for engineering large second-order nonlinear optical polarizabilities is critically analyzed and contrasted with a recent limiting theory for nonlinear molecular polarizability.
Abstract: The combination of two design strategies for engineering large second-order nonlinear optical polarizabilities is critically analyzed and contrasted with a recent limiting theory for nonlinear molecular polarizabilities. Elongation of the conjugation path length and N-arylation in stilbazolium chromophores both are established engineering guidelines to enhance molecular optical nonlinearities. These two strategies have now been combined, resulting in extended and N-aryl substituted “stilbazolium” chromophores. The second-order nonlinear molecular polarizabilities, or first hyperpolarizabilities β, of these ionic compounds were measured by hyper-Rayleigh scattering with suppression of the multiphoton fluorescence contributions. Static first hyperpolarizabilities β0 were estimated by using the two-level model. The resulting large β0 values are compared with theoretical limiting values obtained from recently derived generally applicable sum-rules and with experimental values for neutral dipolar chromophores....

126 citations

Journal ArticleDOI
TL;DR: In this paper, the authors established analytical structure/(hyper)polarizability relationships for donor-acceptor conjugated molecules, within the framework of the two-state approximation.

118 citations

Journal ArticleDOI
TL;DR: In this paper, the process of two-photon absorption by an atom is used as an application of the various interaction Hamiltonians in a discussion of their computational differences and the Lagrangian approach has also been examined to give further insight into the dynamics.
Abstract: In nonrelativistic quantum electrodynamics there is a class of equivalent Hamiltonians that describe a system of radiation and atoms or molecules in interaction. Three specific examples, namely, the minimal coupling, the multipolar, and the space‐translated forms are analyzed here in detail. Their equivalence is demonstrated. The Lagrangian approach has also been examined to give further insight into the dynamics. The equations of motion are compared. Finally, the process of two‐photon absorption by an atom is used as an application of the various interaction Hamiltonians in a discussion of their computational differences.

91 citations

Journal ArticleDOI
TL;DR: In this paper, a detailed theoretical treatment of the hyper Raman effect is presented using the density matrix treatment, which gives information on the frequencies of the scattered radiation, the scattering mechanism and resonance processes.
Abstract: A detailed theoretical treatment of the hyper Raman effect is presented. Using the density matrix treatment we derive general formulae which give information on the frequencies of the scattered radiation, the scattering mechanism and resonance processes. A hyperpolarizability theory analogous to the Placzek polarizability theory is developed and the conditions under which it is valid are established. The enhancement of intensity of hyper Raman scattering through resonance processes is discussed.

83 citations