Experimental research on spectrum and imaging of continuous-wave terahertz radiation based on interferometry

Abstract

A system for measuring terahertz spectrum is proposed based on optical interferometer theory, and is experimentally demonstrated by using a backward-wave oscillator as the terahertz source. A high-resolution, high-precision interferometer is constructed by using a pyroelectric detector and a chopper. The results show that the spectral resolution is better than 1 GHz and the relative error of frequency is less than 3%. The terahertz energy density distribution is calculated by an inverse Fourier transform and tested to verify the feasibility of the interferometric approach. Two kinds of carbon-fiber composites are imaged. The results confirm that the interferometer is useful for transmission imaging of materials with different thickness values.

High-precision terahertz frequency modulated continuous wave imaging method using continuous wavelet transform

“…1 Since THz could penetrate many nonmetallic materials that are opaque in the scope of infrared and visible, and it's not as radioactive as X-rays or attenuating fast like ultrasound, which is used extensively to detect the defects of air hole inside the heat shield in the field of aerospace. [2][3][4] The heat shield is made of the composite material that traditional detection method such as ultrasonic and infrared can't penetrate while THz imaging could provide the hidden information of such materials. In addition, although X-ray has strong penetration, it can't distinguish chemical information of the composite materials.…”