Symmetry and Finite-Size Effects in Quasi-Optical Extraordinarily THz Transmitting Arrays of Tilted Slots

Miguel Camacho,Suzanna Freer,Stefan Dimov,Ajla Nekovic,Rafael R Boix,Pavel Penchev,Miguel Navarro-Cia

doi:10.1109/tap.2020.2985770

Abstract

Extraordinarily transmitting arrays are promising candidates for quasi-optical (QO) components due to their high frequency selectivity and beam scanning capabilities owing to the leaky-wave mechanism involved. We show here how by breaking certain unit cell and lattice symmetries, one can achieve a rich family of transmission resonances associated with the leaky-wave dispersion along the surface of the array. By combining 2-D and 1-D periodic method of moments (MoM) calculations with QO terahertz (THz) time-domain measurements, we provide physical insights, numerical, and experimental demonstration of the different mechanisms involved in the resonances associated with the extraordinary transmission peaks and how these evolve with the number of slots. Thanks to the THz instrument used, we are also able to explore the time-dependent emission of the different frequency components involved.

Highlights

I N THE early 1990s, the extraordinary optical transmission (EOT) phenomenon through subwavelength apertures was discovered [1]–[3] opening the door to new and exciting physics
In contrast to what we find when exploring the dispersion along the x-axis in Fig. 2, at both planes of incidence associated with transverse electric (TE) and transverse magnetic (TM) incidence, the two lightlines associated with the (1,0) and (0,1) harmonics show very similar dispersion relation, enforcing a similar angle-dependence on the EOT peaks
We have provided an extensive study of the EOT phenomenon through periodic and finite arrays of tilted slots, which allows for a very distinguishable simultaneous coupling to two different EOT resonances, in contrast to the highly symmetric arrays traditionally studied in the literature

Summary

INTRODUCTION

I N THE early 1990s, the extraordinary optical transmission (EOT) phenomenon through subwavelength apertures was discovered [1]–[3] opening the door to new and exciting physics. The relationship between the high transmissivity and the periodicity became apparent when the transmission spectrum was mapped for different planes of incidence [5], finding that these peaks correspond to the excitation of optical-frequency surface waves known as surface plasmons [6], [7] These surface waves, usually tightly bound to the surface of a plasmonic material, can become leaky when supported by periodic structures, following the same principle used nowadays by periodically modulated leaky wave antennas [8] and that can be traced back to [9]. We explore both the time-response of the system through spectrography and illumination effects such as polarization and angle of incidence dependencies

THEORY

CONCLUSION