1-D laser beam shaping using an adjustable binary diffractive optical element

We present a theoretical and experimental investigation of a very simple binary Diffractive Optical element referred as a phase slit. The latter is made up of two transparent plates of glass in which a phase step has been patterned using ion beam etching. The two phase steps are set parallel and are able to slide each on the other so that one can adjust continuously the width of the phase shifting zone that suffers an incident Gaussian beam. It is shown that the phase slit is able to make a 1-D transformation of a Gaussian beam either into a uniform profile or a hollow profile having a central depression whose depth can be continuously adjusted just by changing the width of the slit.