Broadband second harmonic generation in potassium tantalate niobate crystals with "2T" engineered domain...

Domain engineering facilitates material property optimization through controlled domain configurations. However, the modulation mechanism of such engineered domains on nonlinear optical (NLO) responses remains unclear. Here, we study second-harmonic generation (SHG) in [110]_c-poled potassium tantalate niobate (KTa_1-xNb_xO₃, KTN) crystals with "2T" domain configuration. Polarization- and wavelength-dependent SHG measurements reveal that such domain configurations achieve type-0 quasi-phase matching (QPM), enabling broadband SHG. Combined experimental and theoretical analyses elucidate the underlying mechanisms responsible for the broadband SHG in KTN crystals. These findings deepen the understanding of the NLO properties of KTN crystals and guide the design of broadband nonlinear optical devices.