Design and fabrication of metasurface engineered antiresonant fibers for polarization dependent terahertz wave modulation.

Fiber-integrated devices give THz applications advanced characteristics of connection with low insert loss, resistance on water vapor absorption, and flexible optical path adjustments. In this paper, an antiresonant fiber (ARF) structure with metasurfaced fiber core was proposed for polarization-dependent THz wave modulation, and the introduction of metasurface on the fiber core makes ARF have a high extinction with the modulation light and a low loss with the transmission light. Constructed by the metasurface coated low-density polyethylene (LDPE) film, the cladding tubes of the ARF were then sealed in a polytetrafluoroethylene (PTFE) shrinkable tube, forming the metasurfaced-core ARF. For the 1-THz wave, a 4-mm core-diameter ARF demonstrated a simulated loss of 0.18 dB for the transmission polarized light, whereas the absorption polarized loss exceeded 100 dB/m. A reasonable fabrication processing was proposed based on the method of "thin-film to optical fiber," and a metasurfaced-core ARF sample with a core diameter of 4 mm and a length of 16 cm was fabricated. Measured with THz time-domain spectroscopy (THz-TDS), the 16.cm length fiber sample showed a light transmission band at approximately the designed 1 THz and a strong polarization-dependent filtering capability with an approximately 7-dB difference in power spectral density.