Terahertz optical scanning imaging of motionless polyurethane insulation materials

Abstract

The authors demonstrate a terahertz optical scanning imaging system which utilises a combined 3D translation platform. Three mirrors are installed on the three sliders of the platform to realise the terahertz beam scanning of the motionless object. A pulsed quantum-cascade laser at the frequency of 4.3 THz and a fast quantum-well photodetector are employed in this terahertz imaging system to research the polyurethane insulation materials. A Fourier transform spectrometer is applied to measure the transmittance of the polyurethane insulation materials from 2 to 8 THz. The terahertz images of the polyurethane foams with a badge or three drops of water are obtained with great contrast.