Mesoscopic radiation reaction in scattering of light by active boundary surfaces

by Prof. Sándor Varró (ELI-ALPS Research Institute, Szeged, Hungary)

Friday 6 Feb 2026, 14:00 → 15:00 Europe/Budapest

We shall discuss the dynamics of reflection and transmission of light pulses at active boundary surfaces, which are very thin conducting layers (metal, transient plasma, graphene) represented by current sheets (they may be embedded in dielectrics). The boundary conditions contain the unknown surface current components, whose electrons move under the action of the Lorentz force, which stems from the superposition of the incoming field and the unknown reflected and transmitted fields. This model gives a special closed set of coupled Maxwell-Lorentz equations, where a damping term automatically appears, as a result of a mesoscopic radiation reaction. The solutions of these equations allow us to predict several new effects, like the modification of the Fresnel coefficients, the appearance of frozen-in electromagnetic pulses [1], and the generation of rectangular optical waves [2]. The latter effect may perhaps be relevant for a physical realization of Haar wavelets [3] in the optical range. We shall also show our results on the time-dependent reflection and refraction of electromagnetic pulses on a system of two parallel current sheets [4]. Here the problem has been reduced to a hybrid system of two-delay differential equations for the electron motion in the layers and a recurrence relation for the scattered fields. The solution has been given as a limit of a singularly pertubed system. Finally, we plan to highlight some similarities of our analysis with the description of the classical radiation reaction problem concerning the early electron models [5].

References.

[1] Varró S : Linear and nonlinear absolute phase effects in interactions of ulrashort laser pulses with a metal nano-layer or with a thin plasma layer. Laser and Particle Beams 25, 379 (2007). E-print: arXiv: physics/0610266 [physics.plasm-ph].

[2] Varró S; Graphene-based carrier-envelope phase difference meter. AIP  Conf. Proceedings 1462, 128 (2012). [2a] Varró S, Generation of rectangular optical waves by relativistic clipping. Laser Physics 23, 056006 (2013). E-print: arXiv:1301.6103 [physics.optics].

[3] Haar A, Zur Theorie der orthogonalen Funktionensysteme (Inaugural Dissertation zur Erlangung der Doktorwürde der hohen philosophischen Fakultät der Georg-August-Universität zu Göttingen, vorgelegt von Alfred Haar aus Budapest). 1909, 1-49; [3a] Haar A, Mathematische Annalen 69, 331-371 (1910); [3b] Haar A, Mathematische Annalen 71, 38-53 (1911).

[4] Polner M, Varró S and Vörös‐Kiss A, The role of the time delay in the reflection and transmission of ultrashort electromagnetic pulses on a system of parallel current sheets. Physica Scripta 94, 045205 (2019). E-print: arXiv: 1812.03857v1 [physics.class-ph].

[5] Spohn H, The critical manifold of the Lorentz-Dirac equation. Europhys. Lett. 50, 287 (2000). [5a] Rohrlich F, The correct equation of motion of a classical point charge. Physics Letters A 283, 276-278 (2001). [5b] Yaghjian A D, Relativistic Dynamics of a Charged Sphere. Updating the Lorentz-Abraham Model, 2nd ed. Lect. Notes Phys. 686 (Springer, New York 2006).