Modelling of adaptive phase-shifting filter cells with optical control based on multilayer structures of phase-change materials

The paper presents the results of modelling the phase shift of a passing optical beam caused by the formation of a layered structure in a controllable cell made of the phase-change material Ge₂Sb₂Te₅ induced by the controlling influence of pulsed laser radiation of short and ultrashort duration. The crystallization of a thin film of Ge₂Sb₂Te₅ is analyzed on the basis of the thermokinetic approach, taking into account the kinetic properties of the material, the energy and duration of the applied laser radiation, the amorphization of the upper layers of the film during rapid heating and the temperature dependence of the kinetic properties. Graphs of the thickness of the crystalline layer in the film material were plotted for each influencing pulsed radiation. From the data on the position of the crystalline layer, the phase shift of the transmitted optical radiation is calculated. Based on the modelling data of the investigated cell, a phase shifter can be constructed to transform an optical beam of arbitrary aperture. The proposed method of controlling the optical beam front by changing the structural state of a thin film can be very promising when accurate and fast tuning of the optical phase transparency is required.

phase shift, optical filters, chalcogenides, Phase Change Materials, thin films, crystallization