Optimization of third harmonic generation in one PPLN ridge waveguide using dual temperature control technique

We fabricate a 20mm periodical poled lithium niobate ridge waveguide for third harmonic generation in C band using the cascade single + single poling structure. Combine with a dual temperature control technique, both SHG and SFG can be optimized individually to have better THG output. The previous reported issues such as the SHG/SFG temperature mismatch due to the material uncertainty and the green absorption under high green output power can therefore be overcome. Temperature-optimized THG therefore can be achieved in one single waveguide unit from low to high power, we achieve >130%/W/W intrinsic THG conversion efficiency in low input power, and >350mW THG output in 520nm under <1W coupled 1560nm input, both the efficiency and the output power are the highest value in the single pass single waveguide configuration to the best of our knowledge.