Sub-THz generation device based on optical difference frequency generation using T-branch LiTaO<sub>3</sub> rectangular waveguide and sapphire (Al<sub>2</sub>O<sub>3</sub>) dielectric waveguide

We propose a novel device for sub-terahertz (sub-THz) signal generation via optical difference frequency generation (DFG). The device features a T-branch waveguide with two components: a LiTaO3 crystal-embedded main waveguide for sub-THz signal generation and a sapphire (Al2O3) dielectric waveguide side branch that acts as a coupler. In the experiment, a 100 GHz signal is successfully generated, and the T-branch configuration efficiently separates the lightwaves from the generated signal, facilitating integration into advanced sub-THz applications. The measured frequency response of the proposed device is in very good agreement with the calculated results.