Polystyrene (PS) as a low index dielectric material in silver-coated hollow glass waveguides (HGW) has been studied as
an alternative to the more conventional Ag/AgI HGWs. Polystyrene was chosen because it has been well characterized
and it is easily dissolved in toluene. The waveguides were made using an electroless, wet chemistry technique. The
absorbance spectrum for polystyrene indicates it will transmit from 1 to 3 &mgr;m and thus, it is useful at the Er:YAG laser
wavelength of 2.94 &mgr;m. For multilayer HGWs, cadmium sulfide is the high index dielectric material.
Terahertz (THz) radiation has important applications in spectroscopy, imaging, and space science. For some of these applications, in particular spectroscopy, a flexible fiber optic could potentially simplify the THz system and enable the user to transmit radiation to remote locations without excessive absorption by atmospheric moisture. To date THz fiber optics and waveguides have been limited to rigid hollow metallic waveguides, solid wires, or short lengths of solid-core transparent dielectrics such as sapphire and plastic. In this paper we report on flexible, hollow polycarbonate waveguides with interior Cu coatings for broadband THz transmission fabricated using simple liquid-phase chemistry techniques. The losses for these hollow-core guides were measured using a tunable, cw single-mode far IR laser. The losses for the best guides were found to be less than four dB/m and the single mode of the laser was preserved for the smaller bore waveguides. Loss calculations of the loss for the HE11 mode reveal that the metal-coated hollow waveguides have much higher loss than for waveguides coated with both metallic and dielectric thin films.
We propose a chalcogenide glass 1-D photonic bandgap (PBG) hollow fiber for the transmission of mid-IR radiation. Its structure consists of an air-core surrounded by alternating rings of high and low refractive index chalcogenide glass supported by a thick polymer coating. Theoretical calculations demonstrate the potential to achieve low transmission losses at 10.6 μm for the HE11 mode. These calculations indicate that the chalcogenide glasses used in the PBG structure should have high index contrast and low extinction coefficients to minimize transmission losses. We present preliminary results of our ongoing efforts to identify a pair of chalcogenide glasses that meet this criterion. A strategy is developed for the fabrication of a drawable chalcogenide glass 1-D PBG hollow fiber preform.