Design and experimental verification of terahertz
wideband filter based on double-layered
metal hole arrays
Lei Rao,
1
Dongxiao Yang,
1,2,
* Le Zhang,
1
Tao Li,
1
and Song Xia
1
1
Department of Information Science & Electronic Engineering, Zhejiang University, Hangzhou 310027, China
2
Research Center for Terahertz Technology, Zhejiang University, Hangzhou 310027, China
*Corresponding author: yangdx@zju.edu.cn
Received 12 August 2011; revised 16 November 2011; accepted 20 November 2011;
posted 23 November 2011 (Doc. ID 152810); published 28 February 2012
A terahertz wideband filter based on double layer metal hole arrays is designed in this paper. A metal
hole array is perforated on a metal layer with a square array of circular air holes. The transmission
characteristics of the electromagnetic waves through the metal hole array can be determined by the ac-
cumulation of in-phase scattering, spoof surface plasmon polaritons, and waveguide modes. The trans-
mission spectrum is tuned by adding another identical layer metal hole array, and a wideband filter can
be formed accordingly. Samples containing double-layered metal hole arrays were fabricated by micro-
machining technology. A wideband filter with center frequency located at 0.8 THz and FWHM reaching
400 GHz was experimentally achieved. © 2012 Optical Society of America
OCIS codes: 240.6680, 050.1220, 120.2440, 260.3090.
1. Introduction
Nowadays, the terahertz (THz) frequency region,
generally referring to the electromagnetic spectrum
from 100 GHz to 10 THz, has drawn much attention
because of the unique properties of THz radiation
and many demonstrated THz applications [
1]. But
technical challenges still exist, and some typical
functional devices such as filters, polarizers, compen-
sators, and modulators are required for further THz
research. There have been reports of various THz fil-
ters such as stopband filter based on nanoporous si-
licon multilayers [
2], tunable filter based on liquid
crystal [
3], and passband filter based on metallic
photonic crystal [
4]. A universal THz filter is pro-
posed recently which can provide low-pass, high-
pass, bandpass and bandstop filtering functionalities
[
5]. However, relatively few studies on broadband fil-
ters are reported. To the best of our knowledge, an
experimental result of ultrabroadband THz filter
has been achieved of one decade width between
0.2 THz and 2.0 THz with an average of 70% trans-
mittance [
6]; for filter design, a passband centered at
1.25 THz with bandwidth of 500 GHz has been rea-
lized [
7]. The structures of these two broadband THz
filters are relatively complicated. The ultrabroad-
band THz filter [
6] contains ten rectangular air holes
with four different lengths and high length-to-width
ratios per unit cell. In our paper, a simple profile de-
sign of a wideband THz filter is proposed, and the
samples have been fabricated by a common mechan-
ical drilling machine.
It is believed that the diffracted evanescent waves
play an important role in determining the dispersion
of the spoof surface plasmon polaritons (SPPs) on the
corrugated perfect electric conductor (PEC) surface
[
8]. These spoof SPPs can give rise to extraordinary
transmissions through a PEC layer perforated with
arrays of subwavelength apertures [
9]. By utilizing
the characteristics of the spoof SPPs, THz wideband
filters based on double-layered metal hole arrays are
1559-128X/12/070912-05$15.00/0
© 2012 Optical Society of America
912 APPLIED OPTICS / Vol. 51, No. 7 / 1 March 2012