Boundary-layer effects on electromagnetic and acoustic extraordinary transmission through narrow slits. (28th October 2020)

• Record Type: Journal Article
• Authors: Brandão, Rodolfo; Holley, Jacob R.; Schnitzer, Ory
• Is Part Of: Proceedings. Volume 476:Number 2242(2020)
• Publication Date: 2020-10-28
• Subjects: extraordinary transmission -- boundary layers -- thermoviscous effects -- matched asymptotic expansions; Physical sciences -- Periodicals; Engineering -- Periodicals; Mathematics -- Periodicals; 500
• DOI: 10.1098/rspa.2020.0444
• Languages: English
• ISSNs: 1364-5021

Abstract

Abstract : We study the problem of resonant extraordinary transmission of electromagnetic and acoustic waves through subwavelength slits in an infinite plate, whose thickness is close to a half-multiple of the wavelength. We build on the matched-asymptotics analysis of Holley & Schnitzer (2019 Wave Motion 91, 102381 (doi:10.1016/j.wavemoti.2019.102381)), who considered a single-slit system assuming an idealized formulation where dissipation is neglected and the electromagnetic and acoustic problems are analogous. We here extend that theory to include thin dissipative boundary layers associated with finite conductivity of the plate in the electromagnetic problem and viscous and thermal effects in the acoustic problem, considering both single-slit and slit-array configurations. By considering a distinguished boundary-layer scaling where dissipative and diffractive effects are comparable, we develop accurate analytical approximations that are generally valid near resonance; the electromagnetic–acoustic analogy is preserved up to a single parameter that is provided explicitly for both scenarios. The theory is shown to be in excellent agreement with GHz-microwave and kHz-acoustic experiments in the literature.