Spectral investigation of higher-order Kerr effects in a tight-focusing geometry.

The role of the Higher-Order Kerr Effects (HOKE) in intensity clamping is experimentally investigated. We fail to observe any evidence of HOKE-based intensity clamping in a tight geometrical focusing experiment. We introduce a polarization-based technique that can distinguish between spectral components from the leading and trailing edges of the pulse. The results of this time-resolved measurement support the ionization theory of intensity clamping.