We report on the realization of a light beam splitting effect based on a light sensitive diffractive structure. The periodic structure is realized in soft composite materials doped with an high performance light sensitive Liquid Crystal. The capability of the structure as tunable beam splitter, is monitored by combining its zero and first diffracted orders in a MC-Zehnder geometry interferometer. The fringe visibility of the interference pattern can be finely controlled by means of an external pump source. Low driving power and short response time are the main features of this light controlled beam splitter.