Terahertz generation from chirped and delayed laser pulses in a periodically poled lithium niobate waveguide

THz generation from chirped and delayed laser pulses using periodically poled lithium niobate (PPLN) traditionally requires high-energy sources and bulky PPLN crystals. However, for compact, integrated, and miniaturized THz-based applications, such systems must be downsized. In this work, we numerically and experimentally demonstrate THz generation in a PPLN waveguide with a cross-section of 500 × 500 µm², pumped with low pulse energies in the microjoule range at a wavelength of 1 µm. Simulations show that tightly focused optical pulses in this configuration achieve significantly higher THz generation efficiency compared to collimated pumping. For a propagation length of 1.6 cm, optimal parameters are identified as a pulse duration of 5 ps and a pump energy between 0.5 and 1 µJ. Experimental validation confirms these findings, yielding a narrowband THz spectrum centered around 488 GHz. This work opens new perspectives for the development of efficient, integrated THz sources for advanced applications in THz photonics, spectroscopy, and high-speed communications.