Highly conducting wire gratings in the resonance region

Abstract

We present a theoretical approach for calculating the fields diffracted by gratings made of highlyconducting wires that have a rectangular shape. The fields between the wires are represented in terms of modal expansions that satisfy the approximated impedance boundary condition. Our results show thatthis procedure is particularly suited to dealing with gold gratings used in the infrared range, a spectral region where the assumption of a perfect conductor does not hold, and where the rigorous modal method assuming penetrable wires exhibits numerical instabilities linked with the high conductivity of gold. Numerical results are presented, and the theory is used to determine wire parameters by fitting theoretical and experimental data.

Shape resonance omni-directional terahertz filters with near-unity transmittance

“…With the assumption that the metal is a perfect conductor, an excellent approximation in the terahertz range, we obtain an exact solution. Boundary matching between cavity mode expansion inside the holes and Rayleigh expansion outside the holes [31] result in the following zeroth order transmittance for the x-polarization: In addition, electric field profile inside the rectangular hole indeed is close to that of the half wavelength mode (not shown). Since the lowest shape resonance frequency is determined by the rectangular dimension in the direction perpendicular to the polarization, we expect that when we rotate the sample by 90 degrees, the shape resonance frequency switches from b c 2 to a c 2 .…”

Fundamental Role of Periodicity and Geometric Shape to Resonant Terahertz Transmission

“…The fields can be expressed in terms of Rayleigh expansions in region I and III and modal expansion in region II [11,46]. The boundary matching is only carried out at the metaldielectric interfaces of I-II and II-III since which are semi-infinite.…”

“…On the other hand, since the 1970s, the optical properties of transmission gratings or grids have been occasionally studied in the microwave, terahertz (THz), and infrared regions [6][7][8][9][10]. In particular, Lochbihler and Depine in 1993 presented a theoretical approach for calculating the fields diffracted by the gratings made of highly conducting wires [11]. Here they calculated Maxwell's equations based on modal expansions inside the metal and Rayleigh expansions outside the metal, applying the theoretical treatments by means of surface impedance boundary condition method [11,12].…”

“…In particular, Lochbihler and Depine in 1993 presented a theoretical approach for calculating the fields diffracted by the gratings made of highly conducting wires [11]. Here they calculated Maxwell's equations based on modal expansions inside the metal and Rayleigh expansions outside the metal, applying the theoretical treatments by means of surface impedance boundary condition method [11,12].…”

Polarization sensitive silicon photodiodes using nanostructured metallic grids

“…16 The dielectric constant of gold is taken from SOPRA database, 17 whereas the refractive index of the glass substrate is considered to be constant ͑1.525͒. Calculated zero order transmission spectra for various wire grids with w = 150 nm, h = 285 nm, and periods ranging from 350 to 600 nm are reported in Fig.…”