13 Jun 2006
Taiwanese researchers make a low-loss terahertz waveguide out of readily available polyethylene fiber.
A terahertz (THz) waveguide made from plastic wire could one day lead to devices such THz fiber endoscopes for medical applications say scientists in Taiwan. To test the idea, the team from National Taiwan University (NTU) successfully used a 17.5 cm long piece of polyethylene fiber to guide 0.310 - 0.360 THz radiation between a photonic transmitter and Si bolometer. (Optics Letters 31 308)
According to the group, most of today's THz set-ups still feature planar or curved metal reflectors. "The fiber makes THz waveguiding more controllable, reliable and flexible compared with the free-space propagation," Chi-Kuang Sun of NTU's Ultrafast Optics Group told Optics.org. "Sensing and spectroscopy applications are likely to benefit, and we are currently developing a THz fiber endoscope."
Sourced from the fishing industry, the 200 micron diameter plastic wire is pre-treated with steam to remove kinks and bends and end polished. Chi-Kuang Sun and his colleagues use a pair of off-axis parabolic mirrors to collimate and couple THz radiation into the fiber with an efficiency as high as 20%.
Once coupled, a large portion of the THz radiation is guided outside the fiber's lossy core with an attenuation constant of less than 0.01 cm-1. The 200 micron diameter fiber is held in place using paper supports, which have low absorption properties in the THz regime.
Encouraged by the performance of its prototype waveguide, the group is looking to commercialize the technology. The project is sponsored by the National Science Council of Taiwan.