1.Key Laboratory of Opto-Electronic Information Processing, Shenyang Institute of Automation, Chinese Academy of Sciences, Shenyang 110169, China 2.The 46th Research Institute of China Electronics Technology Group Corporation, Tianjin 300220, China 3.Institutes for Robotics and Intelligent Manufacturing, Chinese Academy of Sciences, Shenyang 110169, China 4.University of Chinese Academy of Sciences, Beijing 100049, China
Fund Project:Project supported by Youth Innovation Promotion Association of Chinese Academy of Sciences (Grant No. 2019204), the National Natural Science Foundation of China (Grant Nos. 61505089, 61605235), and the Independent Project of Institutes for Robotics and Intelligent Manufacturing, Chinese Academy of Sciences (Grant No. C2019001)
Received Date:12 November 2020
Accepted Date:07 December 2020
Available Online:23 February 2021
Published Online:05 March 2021
Abstract:Laser pumped terahertz (THz) wave up-conversion detection with high sensitivity, fast responsivity and wide frequency band is achieved at room temperature, based on home-made organic nonlinear crystals 4-N,N-dimethylamino-4′-N′-methyl-stilbazolium tosylate (DAST). Green laser pulses pumped KTiOPO4 optical parametric oscillators are utilized as the sources of dual-wavelength near-infrared (NIR) beams (1.3–1.6 μm, for THz-wave difference frequency generation (DFG)) and a single NIR beam (1.2–1.4 μm, for up-conversion detection). The nonlinear medium for both THz-DFG and detection is DAST (grown by CETC-46). A nanosecond-time-resolved THz pulse is obtained with an InGaAs p-i-n photo-diode. The spectrum of the up-converted NIR light is acquired, which allows us to measure the THz frequency indirectly. The sensitivity (also at room temperature) is 4 orders better at 19 THz than the sensitivity of a commercial thermal detector (Golay Cell). The wide frequency band operation is realized with different sets of band-pass filters, which cover the entire range from 3.15 to 29.82 THz except 8.4 THz of the strong absorption peak of DAST. The dynamic range of a THz source based on DFG can be commonly improved by 2–3 orders, by changing the traditional thermal detector with the up-conversion detection. The presented technology can promote the applications of DFG THz source in the fields of high-resolution spectroscopy and imaging. Keywords:terahertz-wave detection/ nonlinear optics/ organic nonlinear crystal/ frequency up-conversion