Characterization of saturable absorbers using an open-aperture Gaussian-beamZscan

Abstract

We present a theoretical investigation on the open-aperture Gaussian-beam $Z$-scan technique for two dominant saturable absorption models, by using the Adomian decomposition method. Analytic expressions of the $Z$-scan traces are deduced for a cw laser and a pulsed laser, respectively; in particular, for performable simulations, the optimal sum upper limit is found. We give an experimental demonstration, in which a side-chain azobenzene polymer poly [6-[1-(4-(4-nitrophenylazo)phenyl) piperazine] hexyl methacrylate] (Pda) film behaves as a test sample. The results manifest that our theory is reasonable and the Pda film is a good saturable absorber at the wavelength of $532\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$.