High-Repetition-Rate Terahertz Generation in QPM GaAs With a Compact Efficient 2- <tex-math notation='LaTeX'>$\mu \text{m}$ </tex-math> KTP OPO

An efficient tunable high-repetition-rate KTiOPO4 (KTP) optical parametric oscillator (OPO) was deployed as a compact terahertz (THz) source for the first time. The KTP OPO was intracavity pumped by an acousto-optical Q-switched Nd:YVO4 laser and emitted two tunable wavelengths near degeneracy. The OPO tuning range extended continuously from 2.068 to 2.191 $\mu \text{m}$ with a maximum output power of 3.29 W at 24 kHz, corresponding to an optical–optical conversion efficiency of 20.69%, believed to be among the highest reported. A periodically inverted quasi-phase-matched GaAs crystal was used to generate the THz wave by the difference frequency generation (DFG) method based on a dual-wavelength laser. The maximum output THz power was $0.6~\mu \text{W}$ at 1.244 THz, and the DFG energy conversion efficiency was $4.32\times 10^{\mathrm {-7}}$ . This provides a potential practical palm-top tunable THz sources for portable applications.