Photoreversible optical nonlinearities of polymeric films containing spiropyran with long alkyl chains

Abstract

It was demonstrated that the third-order optical nonlinearity of polymer films could be reversibly controlled by the photochromic conversion and following J-aggregate formation of spiropyran embedded in an inert polymer matrix. Patterns consisting of areas with high and low third-order nonlinear optical activities were prepared by imagewise exposure of the photochromic films followed by thermal treatment to form thermally stable J aggregates of photoinduced merocyanine in the exposed area. This system could be useful in developing new unconventional optical devices based on optical nonlinearities, including new types of spatial light modulators.

Spiro-oxazine photochromic fiber optical switch

“…For example, spiro-oxazines have recently attracted much attention due to the high yield cleavage of spiro-C-O bond under ultraviolet ͑UV͒ exposure and the nearly total recovery of the back reaction after UV exposure. 4,5 A photochromic optical switch can be based on either the conformational changes 6,7 or the absorption changes 8,9 of the chromophores. For spiro-oxazines, the colorless closed form ͓I, Fig.…”

One- and Two-Photon Absorption of a Spiropyran–Merocyanine System: Experimental and Theoretical Studies

“…Photochromism is defined as the ability to switch an absorbing species between two states differing in their absorption spectra using irradiation with light of a proper wavelength. A number of organic systems are known to exhibit such characteristics including, inter alia, azobenzenes (where the change of the absorption spectra is due to light-induced trans – cis / cis – trans reaction) and spiropyran and diarylethene systems (where light-induced ring closing–opening takes place). − A photochemically induced change of the absorption spectrum of a material is accompanied by changes in other physical properties; in particular, one can expect changes in the material refractive index through the Kramers–Kronig transformation, and because the photochromism leads to changes of the energy levels of the material, it must also have an influence on its nonlinear optical (NLO) properties. − Indeed, previously it has been evidenced that photochromic systems of the spiropyran type could be interesting as second-order NLO switches, i.e., systems in which the second-harmonic generation could be switched on and off, or third-order NLO switches, , where the switching concerns third-harmonic generation. Two-photon phenomena were also used to induce the photochromic reaction. , …”

“…1−3 A photochemically induced change of the absorption spectrum of a material is accompanied by changes in other physical properties; in particular, one can expect changes in the material refractive index through the Kramers−Kronig transformation, and because the photochromism leads to changes of the energy levels of the material, it must also have an influence on its nonlinear optical (NLO) properties. 4−7 Indeed, previously it has been evidenced that photochromic systems of the spiropyran type could be interesting as second-order NLO switches, 8 i.e., systems in which the second-harmonic generation could be switched on and off, or third-order NLO switches, 9,10 where the switching concerns third-harmonic generation. Two-photon phenomena were also used to induce the photochromic reaction.…”

Reversible Diffraction Efficiency of Photochromic Polymer Gratings Related to Photoinduced Dimensional Changes

“…[19] The reversible response of the photochromic compounds to light exposure is proved to be retained when the photochromic molecules are incorporated in macromolecular matrices, where they are homogeneously dispersed forming miscible systems. [19][20][21][22] In addition, in a previous study it was proved that the photochromic transformation between the SP and MC molecules can alter the macroscopic volume of their host polymer matrices reversibly upon light irradiation. In particular, reversible bending of a free-standing SP polymer film, caused by mechanical cycles of contraction/lengthening that are induced and controlled by UV-and green-laser pulses, was monitored.…”