High-energy and ultra-wideband tunable monochromatic terahertz source and frequency domain spectroscopy system based on DAST crystal

摘要

We have demonstrated a high-energy and broadly tunable monochromatic terahertz (THz) source via differencefrequency generation (DFG) in DAST crystal. The THz frequency is tuned randomly in the range of 0.3-19.6 THz, whichis much wider than the THz source based on the inorganic crystal and the photoconductive antenna. The highest energyof 2.53μJ/pulse is obtained at 18.9 THz corresponding to the optical-to-optical conversion efficiency of 1.31×10~（-4）. TheTHz output spectroscopy is theoretically and experimentally explained by DFG process and Raman spectroscopy.Meanwhile, a phenomenon of blue light from the KTP-OPO with tunable and multiple wavelengths was firstly observedand explained. Based on our THz source, an ultra-wideband THz frequency domain system (THz-FDS) withtransmission mode is realized to measure the ultra-wideband THz spectroscopies of typical materials in solid and liquidstates, such as Si, SiC, White PE, water, isopropyl myristate, simethicone, atonlein and oleic acid, etc.. Furthermore, wehave studied the THz spectral characteristic of biomedical tissue in the ultra-wideband THz frequency range of 0.3-15THz to study the biomedical response in the entire THz frequency range, which contains more abundant spectralinformation and was rarely focused with the limit of the THz source.