Multicolor Cerenkov conical beams generation by cascaded-x~(2) processes in radially poled nonlinear photonic crystals

摘要

We observe multiple simultaneous cascaded-x~(2) Cerenkov conical radiations in radially poled nonlinear photonic crystals. By using two incident fundamental waves ω_1 and ω_2, a variety of cascaded nonlinear up-conversion processes occur which result in high-frequency Cerenkov radiations at 2ω_i + ω_j(i,j = 1,2) exhibiting as multicolor conical beams. Two types of phase-matching geometries with different emission angles are demonstrated for each kind of cascaded-x~(2) Cerenkov radiation. The external angle of the Cerenkov radiation exhibits strong dependence on the fundamental wavelengths. The experimental results agree well with the theoretical calculations.