摘要
Terahertz(THz=10^(12) cycles per second,or T-ray)radiation sources are indispensable for modern materials science,chemical and biomedical imaging and sensing,as well as for a broad range of applications in diagnostic systems and advanced telecommunications1,2.The electromagnetic spectrum of the THz radiation is loosely characterized by the frequency range of 0.1−10 THz,or wavelengths between 30μm and 3 mm.In particular,a low photon energy of 4.2 meV or 48 K at 1 THz,which is less than the thermal energy at room temperature,allows precise measurements with a simplified setup and very high signal-to-noise ratio in time-domain pulsed THz spectroscopy2.Since the spectral region is located on the boundary between electronics and photonics,the diversity of the THz sources relies on either frequency up-conversion of electronic sources,such as solid-state photo-switches and radio-frequency(RF)electron-beam accelerators3,or frequency down-conversion of optical sources,such as optical rectification2,3 in nonlinear optical processes and laser-gas interaction induced by twocolor lasers3.Both technologies,however,exploit ultrashort pulse lasers as a driver.In a recent publication,Tian et al.4 at Shanghai Institute of Optics and Fine Mechanics(SIOM)and Nankai University developed a new THz radiation source using a laser-driven wire that generates a femtosecond electron bunch and helical undulator fields to emit THz synchrotron radiation with high efficiency.
