Propagation of Terahertz Pulses on Coplanar Strip-lines on Low Permittivity Substrates and a Spectroscopy Application

Abstract

The authors have investigated the propagation characteristics of the terahertz electrical pulses on the coplanar strip-lines (CPSs) made on low permittivity substrates. By the use of a commercially available plastic whose permittivity is about 2.3 in 1-3 THz, the radiation loss could be made low, and the total attenuation of about 0.2 neper/mm was achieved at 1 THz. As a result, the spectra reaching 3 THz with a dynamic range of about 60 dB were realized even after the 1 mm propagation. Using the CPS device, a spectroscopy of biotin powder is demonstrated over a frequency range up to 2 THz. #

THz wave propagation on strip lines: Devices, properties, and applications

“…In particular, we show that, by the use of low-permittivity dielectric materials, they can support the propagation of electrical pulses whose spectra reaching 3 THz for a distance as long as 1 mm. As an application of these devices, also we demonstrate the THz spectroscopic characterization of liquid and powder specimens [11][12][13]. In addition, we show that even lower attenuation can be realized in quadrupole mode in threestrip CPS (TSCPS) on low permittivity substrate.…”

Integrated On-Chip THz Sensors for Fluidic Systems Fabricated Using Flexible Polyimide Films

“…1(b) and section III) [11]. The generated THz signal propagates along the PGL, which is wrapped around a fluid filled capillary, and is reflected back to the detector from an open-circuit termination.…”

“…In each of these systems, the evanescent electric field propagating along the waveguide can be employed for the analysis of overlaid dielectric materials, by observing changes induced by proximal samples in the transmission of pulses over the length of the waveguide, such as the attenuation or the propagation velocity. Typically, such waveguides are fabricated on crystalline substrates including quartz [6,11], sapphire [12] and GaAs [12], inter alia. The bandwidth of these devices is then often enhanced by mechanical lapping of the substrate material [6], or, more recently by using polymer substrates such as Tsurupica [11] and polyimide [13], which are available as thin films (10s of microns thick).…”

“…Typically, such waveguides are fabricated on crystalline substrates including quartz [6,11], sapphire [12] and GaAs [12], inter alia. The bandwidth of these devices is then often enhanced by mechanical lapping of the substrate material [6], or, more recently by using polymer substrates such as Tsurupica [11] and polyimide [13], which are available as thin films (10s of microns thick). These allow both improved bandwidth and sensitivity whilst also offering the additional benefits of reduced cost and increased durability.…”

Spectroscopy of polycrystalline materials using thinned-substrate planar Goubau line at cryogenic temperatures

“…removing the need for purging, providing an improved frequency resolution and, by confining the evanescent field to a defined area, improving the spatial resolution). 30 Of the three more commonly used on-chip geometries (microstrip-line (MSL), 6 coplanar waveguide (CPW) 7 and planar Goubau lines (PGL)), the greater evanescent field extent 8 of PGLs make them better suited for spectroscopic applications owing to stronger interaction with overlaid materials. However, 35 PGLs have so far been limited to a maximum operational frequency of < 800 GHz for a 1-mm-long transmission line.…”