Optically controlled fine-tuning phase shift cell based on thin-film Ge$_2$Sb$_2$Te$_5$ for light beam phase modulation

Presented the experimental study of free-space optical control of the optical beam phase shift caused by the formation of a layered structure in an elementary controllable cell made of phase-change material Ge$_2$Sb$_2$Te$_5$ subjected to the controlling effect of pulsed laser radiation. The phase change of the signal optical beam passing through the controlled cell from phase-change material relative to the control beam in the Jamin interferometer is demonstrated.