High-sensitive terahertz parametric upconversion detection up to 6 THz in KTP crystal

A highly sensitive terahertz (THz) wave parametric upconversion detector was demonstrated based on KTiOPO_4 (KTP) crystal pumped by a nanosecond 1064-nm laser. The effects of pump energy on the detection sensitivity were studied in this experiment, where the upconversion signal and spontaneous noise were both amplified linearly with the increase of pump energy. The minimum detectable THz wave energy of 57.6 aJ was realized at 5.74 THz under higher pump energy, which gives the dynamic range of 104 dB and noise equivalent power (NEP) of 147.8 fW/Hz^1/2. It was three orders of magnitude higher than that of bolometer. Moreover, a rapid-response detection in the THz frequency range of 5.24 THz-6.14 THz was achieved. This THz parametric upconversion detector based on KTP crystal can provide a technical solution to achieve high-sensitive THz detection in a wide THz region.