EZ-scan: single-beam measurement technique for thin-film nonlinearities

Experimental and theoretical results are given for studies of optical limiters designed to increase the functional range without incurring optical damage. In particular, we investigate a tandem geometry with two passive nonlinear elements, one placed in the focal plane of a lens and the second placed `upstream' of the focal position to protect the material at focus from damage. To provide a proof-of-principle demonstration of this geometry, simple limiters consisting of combinations of reverse saturable absorber dyes and a carbon black suspension in thin cells were tested. Our results show that a substantial increase in device performance can be achieved by use of a tandem limiter geometry. Simple modelling predicts that the dynamic range of a separate- element tandem limiter is given by the product of the dynamic ranges of the individual component limiting elements, in agreement with our experimental results. We also describe our numerical beam propagation code, which must be applied for thick limiting elements and in other cases where simple modelling is invalid.