Lagrangian dynamics of the coupled field-medium state of light

Optical Trapping and Optical Micromanipulation XVI

Tulkki

2019

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The recently introduced mass-polariton (MP) theory of light describes light in a medium as a coupled state of the field and matter [Phys. Rev. A 95, 063850 (2017)]. In the MP theory, the optical force density drives forward an atomic mass density wave (MDW) that accompanies electromagnetic waves in a medium. The MDW is necessary for the fulfilment of the conservation laws and the Lorentz covariance of light. In silicon at wavelength λ 0 = 1550 nm, the atomic MDW carries 92% of the total momentum and angular momentum of light. The MDW of a light pulse having field energy E propagating in a dielectric also transfers a net mass equal to δM = (n p n g − 1)E/c 2 , where n p and n g are the phase and group refractive indices. In this work, we present a schematic experimental setup for the measurement of the MDW in a silicon crystal. This setup overcomes many challenges that have been present in previously introduced setups and that have made the experimental observation of the MDW effect difficult due to its smallness in comparison with other effects, such as the momentum transfer by absorption and reflections. The present setup also overcomes challenges with elastic relaxation effects while extending possible measurement time scales beyond the time scale of sound waves in the setup geometry. For the proposed setup, we also compare the predictions of the MP theory of light to the predictions of the conventional Minkowski theory, where the total momentum of light is carried by the electromagnetic field. We also aim at optimizing experimental studies of the MDW effect using the proposed setup.

Section: Optical and Elastic Forces And Newton's Equation Of Motionsupporting

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Design of an experimental setup for the measurement of light-driven atomic mass density waves in a silicon crystal

Optical Trapping and Optical Micromanipulation XVI

Tulkki

2019

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“…We have also shown in the Appendix that the four-divergence of the MP SEM tensor is zero. For detailed classical field-theoretical foundations of the MP theory of light, see the follow-up works [12,14]. We have finally argued that the GO surface deformations observed in the experiment of Kundu et al [2] are irreversible.…”

Section: Discussionmentioning

confidence: 72%

Comment on “Analysis of recent interpretations of the Abraham-Minkowski problem”

Tulkki

2019

Phys. Rev. A

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In a recent paper [I. Brevik, Phys. Rev. A 98, 043847 (2018)], Brevik analyzed the experiment by Kundu et al. [A. Kundu et al., Sci. Rep. 7, 42538 (2017)] reporting deformation of a graphene oxide (GO) film after it has been irradiated by a laser beam. The two-dimensional atomic force microscope (AFM) line scanning of the deformation of the GO film after switching off the laser beam takes by far too much time for any elastic changes to remain in the AFM scans. Thus, the changes in the GO film are irreversible and the optoelastic model used by Brevik is not applicable. The rough estimates of the kinetic energy and displacement of atoms by the optical force of a light pulse calculated by Brevik are correct, but in making a comparison with the corresponding high-precision results for the kinetic energy and displacement of atoms in our work [M. Partanen et al., Phys. Rev. A 95, 063850 (2017)], the kinetic energy of atoms is confused with their rest energy. The atoms and their masses are displaced forward by the field and their displaced rest energies give rise to an energy flux. The difference of arguments between ours and Brevik's culminates on the question whether the flux of rest energy caused by the displacement of the medium moving with light should be included in the total energy flux. We also show that the four-divergence of the stress-energy-momentum tensor of the mass polariton theory of light is zero.

“…The topologically quantized values of the orbital and spin angular momentum are then obtained by using the photon number calculated as a ratio of the total field energy and the single photon energy in the approximately monochromatic field. This approach is used not only for vacuum but also in dielectrics and it is essentially included also in the recent classical formulation of the mass-polariton theory of light, [2][3][4] which accounts for the optical force-mediated coupling of the field-medium dynamics. In the mass-polariton theory, the quantized value of the angular momentum is shared between the field and the medium.…”

Section: Introductionmentioning

confidence: 99%

Quantum signatures in the classical limit of electromagnetic waves

Tulkki¹,

Complex Light and Optical Forces XIV

2020

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It is common both in the classical and quantum optics to describe the optical field as a superposition of plane waves. However, it is well known that optically active materials emit photons vastly dominantly in the electric dipole approximation. The photons emitted in the electric dipole transitions are not plane waves, but spherical photon states corresponding to eigenstates J = 1 of the total angular momentum and M = ±1 of the z component of the total angular momentum. In addition, electric dipole photons are separated from the magnetic photons by the state index η = e for electric photons in distinction to η = m for magnetic photons. In this work, we study the far-field that is generated when a two-dimensional matrix of atoms emits electric dipole photons and compare this far-field at large distance from the emitting atomic matrix with a plane wave. The goal of our work is to find out if the light emitted from the electric dipole transitions carry the memory of being electric dipole photons when they are far from the emitting atoms. In particular, it is well known that a plane wave includes all angular momentum components corresponding to quantum numbers J = 1, 2, 3, ..., while the far field of the electric dipole photons emitted by the atomic matrix can include only the angular momentum component J = 1. Although the two-dimensional atomic matrix used as a light source in our simulations is certainly nontrivial to fabricate, it is nevertheless fully physical and we expect that with some modifications, the conclusions from the present simulations can be generalized to atomic light sources that are more easy to realize experimentally.