Nonlinear optical limitation of laser radiation power in the ultraviolet and visible ranges by bis-phthalocyanines of the clamshell type

UV and visible laser radiation poses a high risk to the eyes. Interaction of a beam with a high energy fluence with eye tissues causes damages, including irreversible damage to the cornea or lens. The visible laser radiation destroys a retina. Dangerous level of radiation is achieved in nanosecond pulses, which makes it difficult to use active protective equipment. In a time shorter than the pulse duration, the attenuation of laser radiation is ensured by the use of nonlinear optical materials, for which clamshell-type bis-phthalocyanines were studied and metal complexes $\mathbf{1a,b}$ ($\mathbf{a}$ – Zn, $\mathbf{b}$ – Mg) and the original ligand $\mathbf{2}$. The experiments were carried out in UV and visible range of the spectrum at wavelengths 355, 405 and 532 nm. Using the correlation method for assessing the efficiency of optical limitation (CORRELATO algorithm), it was shown that metal complexes have priority over the ligand, while the maximum efficiency was found for zinc complex $\mathbf{1a}$ in the UV range.