Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Physical Review Letters

QED-vacuum confinement of inelastic quantum scattering at optical frequencies: A new perspective in Raman spectroscopy

Francesco Cairo, F. De Martini, D. Murra

Published Mar 8, 1993• 53 citations
Publisher

Abstract

The spontaneous Raman effect in ${\mathrm{C}}_{6}$${\mathrm{H}}_{6}$ is investigated in the QED-vacuum confinement condition in the Casimir topology of an optical microcavity as a prototype inelastic quantum-scattering process at optical frequencies. The confinement determines a dramatic enhancement (over a factor of ${10}^{3}$), inhibition, and directional effects on the scattering intensity. Apart from its relevance in atomic and molecular spectroscopy, the work establishes a new perspective in the field of QED scattering involving quantum particles with any energy.

DOI
10.1103/physrevlett.70.1413

Related papers

Molecular Raman effect in the optical microcavity: QED vacuum confinement of an inelastic quantum scattering process

F. De Martini, Michele Marrocco, C. Pastina +1 more

The spontaneous Raman scattering from liquid samples of ${\mathrm{C}}_{6}$${\mathrm{H}}_{6}$ is investigated in the Casimir topology of a microscopic optical Fabry-P\'erot cavity terminated by Bragg reflectors tuned at the emitted Stokes wavelength. The given general quantum scattering theory is based on a complete set of mode functions describing the cavity-confined field in its vacuum state. The coupling of the field with the normal CH ring stretching mode at \ensuremath{\Delta}\ensuremath{\nu}=3062 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ (totally symmetric species ${\mathit{A}}_{1\mathit{g}}$) of the benzene molecule is given via the related Raman tensor, which leads to the appropriate form of the coupling Hamiltonian. A detailed experimental investigation of the spontaneous Raman scattering for the mode is then reported. The results confirm the relevant predictions of the scattering theory, namely, the effect of the vacuum confinement on the enhancement and inhibition of the total and differential cross sections, on the angular distribution of the scattered radiation, and on the molecular depolarization ratio. \textcopyright{} 1996 The American Physical Society.

Physical Review A•Jan 1, 1996•9 citations

Lasing inside microcavities without resorting to the concept of density of states: The effects of vacuum field fluctuations

Tracy Robertson, Serge Gauvin

It has long been established that inside microcavities the resulting electromagnetic (optical) confinement might lead to strong enhancement (Purcell effect) or inhibition (Kleppner effect) of spontaneous emission. In both cases, the formulation is based on the concept of density of optical modes. However, and without resorting to this concept, there is an alternative point of view entirely based on the modulation of the vacuum field fluctuations. Consequently, a different interpretation of lasing, which does not involve the concept of density of modes, is conceivable.

Photonics North (PN)•Jun 1, 2017•2 citations

Spontaneous Scattering of Raman Photons from Cavity-QED Systems in the Ultrastrong Coupling Regime

Vincenzo Macrí, Alberto Mercurio, Franco Nori +2 more

We show that spontaneous Raman scattering of incident radiation can be observed in cavity-QED systems without external enhancement or coupling to any vibrational degree of freedom. Raman scattering processes can be evidenced as resonances in the emission spectrum, which become clearly visible as the cavity-QED system approaches the ultrastrong coupling regime. We provide a quantum mechanical description of the effect, and show that ultrastrong light-matter coupling is a necessary condition for the observation of Raman scattering. This effect, and its strong sensitivity to the system parameters, opens new avenues for the characterization of cavity QED setups and the generation of quantum states of light.

arXiv:2207.09470•Jul 19, 2022•1 citation

Molecular Raman effect in an optical microcavity: A classical approach

Michele Marrocco

Spontaneous Raman scattering is investigated theoretically by considering a completely classical description of the process that takes place within the mirrors of a microscopic Fabry-P\'erot cavity. This analysis is based on the image method within the framework of the classical theory of light scattering. In order to account for the finite reflectivities of the mirrors, the result for the scattered field is presently determined analytically only in the limit of low finesse of the optical cavity. This leads to a general expression for the cross section of the Stokes transition that explains the results recently reported in the literature [F. De Martini, M. Marrocco, C. Pastina, and F. Viti, Phys. Rev. A 53, 471 (1996)]. Therefore, in the limit of low finesse of the cavity, one must accept that this effect has a fundamentally classical nature. \textcopyright{} 1996 The American Physical Society.

Physical Review A•Oct 1, 1996•4 citations

Atoms in micron-sized metallic and dielectric waveguides

Edward A. Hinds, K. S. Lai, M. Schnell

Over the past ten years, our group has investigated the effects of confinement on atoms inside metallic micron–sized cavities in order to elucidate some basic phenomena in the field of cavity quantum electrodynamics (QED). The first of these was the inhibition of spontaneous emission from an atom inside a cavity. This was followed by a laser spectroscopic measurement of the van der Waals interaction between a single Rydberg atom and a gold cavity, which showed that a simple electrostatic model of the atom–cavity interaction is correct when the cavity is small enough. More recently, the retarded Casimir–Polder force was measured between a ground state sodium atom and a large cavity, demonstrating that the van der Waals potential fails at long enough range and that the vacuum fluctuations of the field then have an important role in the interaction of the atom with the cavity. Our group is now pushing forward these investigations to study cavities whose walls have losses and dispersion, where the theory of cavity QED is significantly more complicated. With real surfaces, we have to deal with the complex dielectric response ε(ω) of the material, which exhibits frequency–dependent absorption and dispersion. One particularly interesting case is when a downward transition in the atom is resonant with an excitation of the cavity walls. This opens a new branch for the atomic decay: as an alternative to creating a photon within the space surrounded by the cavity walls the atomic decay can now create an electromagnetic excitation of the walls themselves. Another novel feature of our experiments is that the Bohr frequencies of the atom are close to the kT/h, where T is room temperature. We therefore expect to be able to measure effects associated with QED at finite temperature; in other words, to study how the blackbody radiation affects our experiments. By conducting experiments with real surfaces, we hope to elucidate and perhaps simplify the theoretical models used to describe these systems.

Philosophical Transactions of the Royal Society A Mathematical Physical and Engineering Sciences•Dec 15, 1997•22 citations

Vacuum Confinement Effects on Molecular Dynamics in a Microscopic Cavity

F. De Martini

Several experimental schemes of vacuum-confinement in electromagnetic-bounded structures are presented together with related results involving Spontaneously Emitting (SE) molecules. Striking anomalies in the SE spatial-distribution and decay-times are detected. In addition, an anomalous "zero-threshold-laser" behaviour of molecular Stimulated Emission (StE) in a single-mode Casimir-type microscopic cavity is reported. This novel effect is due to an unexpected collective molecular process taking place at an exceedingly low excitation level in the optical-pumping scheme. In the framework of "Phase-transition" theory this effect corresponds to an order-disorder transition taking place at a critical-temperature T c which is virtually infinite.

Physica Scripta•Jan 1, 1988•14 citations
The spontaneous Raman effect in {\mathrm{C}}_{6}$${\mathrm{H}}_{6} is investigated in the QED-vacuum confinement condition in the Casimir topology of an optical microcavity as a prototype inelastic quantum-scattering process at optical frequencies. The confinement determines a dramatic enhancement (over a factor of 103{10}^{3}103), inhibition, and directional effects on the scattering intensity. Apart from its relevance in atomic and molecular spectroscopy, the work establishes a new perspective in the field of QED scattering involving quantum particles with any energy.
The spontaneous Raman scattering from liquid samples of C6{\mathrm{C}}_{6}C6​H6{\mathrm{H}}_{6}H6​ is investigated in the Casimir topology of a microscopic optical Fabry-P\'erot cavity terminated by Bragg reflectors tuned at the emitted Stokes wavelength. The given general quantum scattering theory is based on a complete set of mode functions describing the cavity-confined field in its vacuum state. The coupling of the field with the normal CH ring stretching mode at \ensuremath{\Delta}\ensuremath{\nu}=3062 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ (totally symmetric species A1g{\mathit{A}}_{1\mathit{g}}A1g​) of the benzene molecule is given via the related Raman tensor, which leads to the appropriate form of the coupling Hamiltonian. A detailed experimental investigation of the spontaneous Raman scattering for the mode is then reported. The results confirm the relevant predictions of the scattering theory, namely, the effect of the vacuum confinement on the enhancement and inhibition of the total and differential cross sections, on the angular distribution of the scattered radiation, and on the molecular depolarization ratio. \textcopyright{} 1996 The American Physical Society.
It has long been established that inside microcavities the resulting electromagnetic (optical) confinement might lead to strong enhancement (Purcell effect) or inhibition (Kleppner effect) of spontaneous emission. In both cases, the formulation is based on the concept of density of optical modes. However, and without resorting to this concept, there is an alternative point of view entirely based on the modulation of the vacuum field fluctuations. Consequently, a different interpretation of lasing, which does not involve the concept of density of modes, is conceivable.
We show that spontaneous Raman scattering of incident radiation can be observed in cavity-QED systems without external enhancement or coupling to any vibrational degree of freedom. Raman scattering processes can be evidenced as resonances in the emission spectrum, which become clearly visible as the cavity-QED system approaches the ultrastrong coupling regime. We provide a quantum mechanical description of the effect, and show that ultrastrong light-matter coupling is a necessary condition for the observation of Raman scattering. This effect, and its strong sensitivity to the system parameters, opens new avenues for the characterization of cavity QED setups and the generation of quantum states of light.
Spontaneous Raman scattering is investigated theoretically by considering a completely classical description of the process that takes place within the mirrors of a microscopic Fabry-P\'erot cavity. This analysis is based on the image method within the framework of the classical theory of light scattering. In order to account for the finite reflectivities of the mirrors, the result for the scattered field is presently determined analytically only in the limit of low finesse of the optical cavity. This leads to a general expression for the cross section of the Stokes transition that explains the results recently reported in the literature [F. De Martini, M. Marrocco, C. Pastina, and F. Viti, Phys. Rev. A 53, 471 (1996)]. Therefore, in the limit of low finesse of the cavity, one must accept that this effect has a fundamentally classical nature. \textcopyright{} 1996 The American Physical Society.
Over the past ten years, our group has investigated the effects of confinement on atoms inside metallic micron–sized cavities in order to elucidate some basic phenomena in the field of cavity quantum electrodynamics (QED). The first of these was the inhibition of spontaneous emission from an atom inside a cavity. This was followed by a laser spectroscopic measurement of the van der Waals interaction between a single Rydberg atom and a gold cavity, which showed that a simple electrostatic model of the atom–cavity interaction is correct when the cavity is small enough. More recently, the retarded Casimir–Polder force was measured between a ground state sodium atom and a large cavity, demonstrating that the van der Waals potential fails at long enough range and that the vacuum fluctuations of the field then have an important role in the interaction of the atom with the cavity. Our group is now pushing forward these investigations to study cavities whose walls have losses and dispersion, where the theory of cavity QED is significantly more complicated. With real surfaces, we have to deal with the complex dielectric response ε(ω) of the material, which exhibits frequency–dependent absorption and dispersion. One particularly interesting case is when a downward transition in the atom is resonant with an excitation of the cavity walls. This opens a new branch for the atomic decay: as an alternative to creating a photon within the space surrounded by the cavity walls the atomic decay can now create an electromagnetic excitation of the walls themselves. Another novel feature of our experiments is that the Bohr frequencies of the atom are close to the kT/h, where T is room temperature. We therefore expect to be able to measure effects associated with QED at finite temperature; in other words, to study how the blackbody radiation affects our experiments. By conducting experiments with real surfaces, we hope to elucidate and perhaps simplify the theoretical models used to describe these systems.
Several experimental schemes of vacuum-confinement in electromagnetic-bounded structures are presented together with related results involving Spontaneously Emitting (SE) molecules. Striking anomalies in the SE spatial-distribution and decay-times are detected. In addition, an anomalous "zero-threshold-laser" behaviour of molecular Stimulated Emission (StE) in a single-mode Casimir-type microscopic cavity is reported. This novel effect is due to an unexpected collective molecular process taking place at an exceedingly low excitation level in the optical-pumping scheme. In the framework of "Phase-transition" theory this effect corresponds to an order-disorder transition taking place at a critical-temperature T c which is virtually infinite.