THz imaging by a compact free-electron laser

We have developed a laboratory-scale users facility with a compact TeraHertz (THz) Free Electron Laser (FEL). The FEL operates in the wavelength range of 100-1200μm, which corresponds to 0.3-3 THz. THz radiation from the FEL shows well collimated Gaussian spatial distribution and narrow spectral width of Δλ/λ∼0.003, which is Fourier transform limited by the estimated pulse duration of 20 ps. The main application of the FEL is THz imaging for bio-medical researches. We are developing THz imaging techniques by 2-dimensional (2-D) scanning, single pulse capturing with the electro-optic method, and 3-D holography. High power, coherent, and pulsed feature of the FEL radiation is expected to show much better performance in advanced THz imaging of 3-D tomography. The coherent length of the FEL micropulse is measured to be 8-12 mm. In this paper we will show and discuss the main results of THz imaging by using the KAERI compact FEL