Light-sensitive liquid films are used to produce cross modulation between light beams in an all-optical setup. Two light beams are superimposed in the same region of the film. The samples are black oils whose physical properties strongly depend on the temperature. The liquid film is deformed by heating with the first light beam, thus changing the divergence of the other one. In the first setup presented in this paper the power concentration per unit area of a laser beam (HeNe, cw, 1 mW) is switched from a maximum to a minimum value and conversely) following the intensity variations of another laser beam (HeNe, cw, 10 mW). The time required to change the power concentration from 0.1 mW/mm2 to 10-3 mW/mmz is about 100 ms. In another setup, large-scale deformations of the liquid film (diameter about 5 mm ) are induced by heating with a white-light beam. The deformed region behaves as a mirror whose curvature radius depends on the intensity of the light beam. This allows one to form the real image of a 3-D object through the mirror and to switch it on and off by chopping the light beam. A typical switching time is about 1 s.
German Da Costa,
"All-Optical Light Switch Using Interaction Between Low Power Light Beams In A Liquid Film," Optical Engineering 25(9), 251058 (1 September 1986). https://doi.org/10.1117/12.7973954