Hollow optical fibers loaded with an inner dielectric film for terahertz broadband spectroscopy

A design method for hollow optical fibers is shown that has a dielectric cover film loaded on the inner metal coating to obtain flexible fiberoptics transmitting a wide wavelength range in THz region with low loss. Spectral losses of fibers that are fabricated by two different methods are measured by using a broadband THz source. The loss of a fiber with an inner diameter of 3 mm was 1.3 dB/m at the wavelength of 200 μm, and the losses were lower than 3 dB in the wavelength region from 150 μm to > 250 μm. Because these fibers are flexible, robust, and highly efficient in a wide wavelength range, they are useful in remote THz spectroscopy.