Energy scaling and extended tunability of a ring cavity terahertz parametric oscillator based on KTiOPO4 crystal**Project supported by the National Basic Research Program of China (Grant Nos. 2015CB755403 and 2014CB339802), the National Key Research and Development Program of China (Grant No. 2016YFC0101001), the National Natural Science Foundation of China (Grant Nos. 61775160, 61771332, and 61471257), China Postdoctoral Science Foundation (Grant

Abstract

A wide terahertz tuning range from 0.96 THz to 7.01 THz has been demonstrated based on ring-cavity THz wave parametric oscillator with a KTiOPO4 (KTP) crystal. The tuning range was observed intermittently from 0.96 THz to 1.87 THz, from 3.04 THz to 3.33 THz, from 4.17 THz to 4.48 THz, from 4.78 THz to 4.97 THz, from 5.125 THz to 5.168 THz, from 5.44 THz to 5.97 THz, and from 6.74 THz to 7.01 THz. The dual-Stokes wavelengths resonance phenomena were observed in some certain tuning angle ranges. Through the theoretical analysis of the dispersion curve of the KTP crystal, the intermittent THz wave tuning range and dual-wavelength Stokes waves operation during angle tuning process were explained. The theoretical analysis was in good agreement with the experiment results. The maximum THz output voltage detected by Golay cell was 1.7 V at 5.7 THz under the pump energy of 210 mJ, corresponding to the THz wave output energy of 5.47 μJ and conversion efficiency of 2.6 × 10−5.