Broadband Asymmetric Conical Emission via Cascaded Second-Order Nonlinear Polarization during the Propagation of Femtosecond Laser Pulses in a BBO Crystal

We investigate the propagation of femtosecond laser pulses in a 5-mm-thick BBO crystal along the direction of type-I phase-matched second-harmonic generation. An intensity-asymmetric broadband conical emission (500–2000 nm) is demonstrated when a suitable chirp is introduced. It is generated by optical parametric amplification pumped by the second-harmonic light and seeded by the fundamental light which is broadened by cascaded nonlinear processes during second-harmonic generation.