Polarization-dependent colored conical emission in a quadratically nonlinear medium

Both supercontinuum conical emission (SCCE) and blue-green conical emission (CE) by means of second harmonic generation (SHG) were observed alternately in a β-barium borate (BBO) crystal induced by femtosecond laser pulses with vertical polarization state. Three theoretical models were analyzed to interpret the angular beam of SCCE. The experimental conical angles with different wavelengths in BBO crystal and BK-7 glass can be explained well by nonlinear X-wave model and Cerenkov type phase matching model other than four-wave mixing (FWM) model.