Generation and characterization of intense terahertz pulses from DSTMS crystal

Matter manipulation in terahertz range calls for strong-field broadband light source. Here, we present a scheme for intense terahertz generation from DSTMS crystal driven by a high power OPCPA with 13 mJ pulse energy, 137 fs pulse duration, 1.45 μm center wavelength and 20 Hz repetition rate. The DSTMS crystal is a single crystal with 12 × 8 mm2 usable area and 420 μm thickness. The electric field and spectrum of the THz radiation are characterized by electro-optical (EO) sampling measurement. The main lobe of THz pulse contains about 1.5 THz cycles. The THz spectrum covers 0.1-4.5 THz. The carrier frequency of the pulse can be calculated to be about 2 THz according to the spectrum. The relationship between terahertz energy, conversion efficiency and pump fluence is demonstrated. With the increase of pump fluence, the THz energy basically increases, while the conversion efficiency increases to saturation and then decreases slightly. In the experiment, the pump fluence of 15.6 mJ/cm2 is the inflection point of the THz energy curve and also the starting point of saturation of conversion efficiency. With 10 mJ pump energy (corresponding to ~26 mJ/cm2 pump fluence), the generated THz pulse energy reaches 175 μJ, the conversion efficiency correspondingly reaches 1.73%, and the electric field is about 17 MV/cm at the focus. This study promotes the intense THz generation based on OPCPA facilities and provides the possibility for multiband high field terahertz pump-probe experiments.