Highly sensitive multi-stage terahertz parametric upconversion detection based on a KTiOPO4 crystal

In this Letter, we demonstrate a highly sensitive multi-stage terahertz (THz) wave parametric upconversion detector based on a KTiOPO4 (KTP) crystal pumped by a 1064-nm pulsed-laser (10 ns, 10 Hz). The THz wave was upconverted to near-infrared light in a trapezoidal KTP crystal based on stimulated polariton scattering. The upconversion signal was amplified in two KTP crystals based on non-collinear and collinear phase matching, respectively, to improve detection sensitivity. A rapid-response detection in the THz frequency ranges of 4.26-4.50 THz and 4.80-4.92 THz was achieved. Moreover, a dual-color THz wave generated from THz parametric oscillator using KTP crystal was detected simultaneously based on dual-wavelength upconversion. The minimum detectable energy of 2.35 fJ was realized with a dynamic range of 84 dB at 4.85 THz, which gives a noise equivalent power (NEP) of the order of 21.3 pW/Hz(1/2). By changing the phase-matching angle or the wavelength of the pump laser, it is suggested that the detection of the THz frequency band of interest in a wide range from approximately 1 to 14 THz is possible. (c) 2022 Optica Publishing Group

Automated summary

This study demonstrates a highly sensitive multi-stage terahertz wave detector based on parametric upconversion. By utilizing a KTiOPO4 crystal, the terahertz wave is converted into near-infrared light, and detection sensitivity is improved through signal amplification using phase matching techniques. The detector exhibits rapid response in the frequency ranges of 4.26-4.50 THz and 4.80-4.92 THz, and simultaneous detection of dual-color terahertz waves is achieved.