2-D Terahertz Metallic Photonic Crystals in Parallel-Plate Waveguides

Abstract

2-D metallic photonic crystals without defects, with point defects, and with a Fabry-Perot (F-P) defect are characterized by terahertz time-domain spectroscopy. The metal parallelplate waveguide (PPWG) with single TEM-mode propagation is used as a tool to simulate 2-D photonic crystals in free space. The 2-D metallic photonic-crystal structures were fabricated by coating Au on an SU-8 polymer cylinder array. Wide terahertz bandgaps were observed in the photonic crystals within the PPWG. The experimental measurements have excellent agreement to 2-D photonic-crystal theory without defects. Defect modes are observed in the samples with defects and show the F-P defect has a strong localization effect.

Improved Bend Waveguide Design for Terahertz Transmission

“…4, the transmission spectrum of 2D geometry coincides with that of the 3D geometry and is comparable to reported works [15,33,34]. The transmission characteristic of a linear waveguide matches the band-gap and dispersion characteristics of single-and double-line defect linear waveguides.…”

“…Metallic photonic crystals have been studied mostly in microwave and millimetre frequency range due to their low propagation losses [9][10][11]. They have also been used in THz frequency range to study their filtering and wave guiding capability [12][13][14][15][16]. However, to the best of the authors' knowledge, a study of THz metallic photonic crystal bends has not been carried out.…”

Terahertz conductivity of thin metal films

“…6,7 For our case of a 88 nm Al film with a conductivity of =16͑⍀͒ −1 , n 2 = ͑1+i͒370 at 1 THz, the resulting amplitude attenuation traversing a single pass within the metal film ͓i.e., exp͑−␣z͔͒ is only 49%, illustrating that the low transmission of these films is dominated by the high reflections from surfaces 1,2 and 2,3. Given the high reflectivity of these metal films, the amplitude transmission t tended to be low, on the order of 10 −2 -10 −3 , corresponding to a power transmission on the order of 10 −4 -10 −6 .…”

“…The amplitude transmission at a frequency f of the films and wafers can be modeled by the thin film formula where t ij and r ij are the complex Fresnel transmission and reflection coefficients, 4 respectively, medium 1 and 4 are vacuum, medium 3 is Si with a thickness d = 0.43 mm and with a THz frequency independent index n 3 = 3.4175 and negligible terahertz absorption, 5 and medium 2 is the metal film with a thickness of h and a complex index 4,6 of…”

Terahertz Wave Transmission Properties of Metallic Periodic Structures Printed on a Photo-paper

“…Metallic periodic structures are also useful in improving radiation efficiency and patterns of antennas in microwave and millimeter wave ranges [4,5]. Thus periodic structures are expected to be useful in manipulating THz waves and could act as functional devices in a THz frequency range [6][7][8][9][10].…”