Optical limiting threshold in carbon suspensions and reverse saturable absorber materials.

I report on the measurement of threshold energy fluence for optical limiting of nanosecond and microsecond pulses in a high-performance carbon suspension known as Defence Research Establishment Valcartier carbon black suspension (CBS)-100. Thresholds as low as 24-mJ/cm(2) (nanosecond regime) and 100-mJ/cm(2) (microsecond regime) have been obtained. The measurement technique, based on an f/20 optical system and a small analysis aperture, has been tested by measurement of reverse saturable absorber materials and other carbon suspensions whose properties can be found in the technical literature. A factor of merit has emerged from these measurements that could be used to order by limiting performance the different types of carbon suspension. In this ordering, CBS-100 appears as the best choice in the set of suspensions tested for short and long pulses.