Ultrafast all-optical tunable Fano resonance in nonlinear ferroelectric photonic crystals

We report an ultrafast all-optical tunable Fano resonance in a nonlinear ferroelectric photonic crystal made of polycrystal lithium niobate, which provides a large nonlinear susceptibility because of strong quantum size effect of nanoscale crystal grains. The femtosecond pump and probe method is adopted to measure the tunability of the Fano resonance based on the nonlinear optical Kerr effect. A 37-nm shift in the Fano resonance wavelength is obtained under excitation of a 30 MW/cm2 pump laser. An ultrafast response time of 43 ps is achieved due to fast relaxation dynamics of bound electrons in polycrystal lithium niobate.