Fine structure of Surface Relief Gratings: experiment and a generic stochastic Monte Carlo model of the photoinduced mass transport in azo-polymer

We study experimentally and theoretically a double-peak fine structure of Surface Relief Gratings in azo-functionalized poly(etherimide). For the theoretical analysis we develop a stochastic Monte Carlo model for photoinduced mass transport in azobenzene functionalized polymer matrix. The long sought-after transport of polymer chains from bright to dark places of the illumination pattern is demonstrated and characterized, various scenarios for the intertwined processes of build-up of density and SRG gratings are examined. Model predicts that for some azo-functionalized materials double-peak SRG maxima can develop in the permanent, quasi-permanent or transient regimes.