Fabrication and characterization of improved Ag/PS hollow-glass waveguides for THz transmission

Abstract

This study involves the fabrication and characterization of improved quality silver (Ag)/polystyrene (PS) thin-film-coated hollow-glass waveguides for the low-loss transmission of terahertz radiation via modified dynamic liquid phase deposition techniques. High-quality PS thin films were deposited from aqueous PS solutions, and the spectral response of fabricated samples was measured from λ=1-100 μm. Fabricated samples exhibited highly defined spectral responses throughout this entire range indicative of PS films of excellent quality. The spectra of experimental samples were compared to the theoretical and bulk PS spectra in the near-IR and far-IR regions. The thickness of deposited PS thin films was found to depend on total sample length and to vary from approximately 10-16 μm for sample lengths ranging from 115 to 140 cm. Such PS film thicknesses are adequate for low-loss delivery from approximately 2-4 THz. Furthermore, film thickness was found to vary minimally along the waveguide length regardless of total sample length.

Terahertz wave transmission in flexible polystyrene-lined hollow metallic waveguides for the 25-5 THz band

“…The experimental spectrum is consistent with the prediction that transmission loss is minimal for this waveguide at ~3-4 THz [14]. The small amount of power output at frequencies above 2.5 THz in the TDS system however does not allow us to characterize transmission in this frequency range.…”

“…The PS-lined hollow metallic waveguide under study here consists of a 1 mm bore diameter fused silica capillary tube with a ~0.6 μm thick Ag film on the internal face and additional 10 ± 1 μm thick PS inner coating [14]. Details of the fabrication can be found in Ref.…”

“…Outside the transmission band, waveguide absorption increases to a level over 20 dB/m due to changes in the hybrid mode profile. The experiments discussed below are designed to verify the predicted behavior [14].…”

“…3(a), 3(b)]. The measured frequency range covers both the lowfrequency absorption band and a large portion of the transmission band [8,14]. The rapid oscillations observed in both waveform spectra on top of a base line, which is associated to the HE 11 mode, accounts for the presence of the HE 12 mode [ Fig.…”

“…Although the loss can be minimized by increasing the waveguide diameter, waveguide flexibility for large diameters reduces and the number of undesired modes increases. Flexible waveguides have been recently fabricated using small diameter (~1 mm) glass tubes coated with silver and polystyrene (PS) layers and the quality of the PS film investigated at midinfrared wavelengths [14]. The small diameter permits bending this waveguide to a radius of 100-150 mm [ Fig.…”