Double-groove terahertz chirped grating waveguide tube for gas pressure detection

A PMMA grating waveguide tube-based terahertz (THz) gas pressure sensor was developed, and the transmission properties were investigated experimentally and theoretically. A double-groove chirped grating structure with a gradient etching depth was adopted to enhance the extinction ratio and improve the detection sensitivity. Nitrogen pressure detection was realized and compared between the tube waveguides with and without the grating structure by a THz time-domain spectroscopy system. The results indicate that a better extinction ratio and detection sensitivity can be realized with the double-groove chirped grating waveguide tube, which can achieve a pressure detection sensitivity of 26.33 dB MPa^-1. The presented double-groove chirped grating waveguide tube with a gradient etching depth is expected to have wide application prospects for THz gas sensing applications.