Optical limiting of ultrashort pulses by carbon black suspension

This work reports on the performance of a carbon black suspension (CBS) working as an optical limiter at the sub-nanosecond regime. Although this material is known to be inefficient at this time scale, we show that its limiting action can be enhanced with a multipass configuration due to the accumulative effect that is provided when the laser beam is repeatedly focused inside the nonlinear medium. We also show that the focusing produced by the self-phase modulation of femtosecond pulses is deleterious to the accumulative process and the limiting is not as good as for picosecond pulses. PACS PACS 42.65.-k; 42.65.Sf; 78.40.Dw