We present a novel type of diffractive optical elements - a nonlinear spiral phase plate whose transmission function is described as exp(iφmn). The light field generated by the element has a spiral-shaped intensity and phase distribution, a non-uniform orbital angular momentum (OAM) distribution and spiral-shaped energy flow. Because of the non-linear azimuthal phase variation, the nonlinear spiral phase plates demonstrate angle-dependent distortion resistance properties. We believe that the proposed nonlinear spiral phase plates will be useful for the realization of OAM-Mode Division Multiplexing in optical communication systems as well as in the area of laser manipulation and laser-matter interaction for fabrication of unique chiral metasurfaces that can be used in optical communication systems too.
We experimentally investigate a novel type of diffractive optical element – a nonlinear spiral phase plate. In contrast to the conventional spiral phase plates, the transmission function of the new element is described as exp(imφn ). The intensity distributions generated by these elements have a spiral shape with an intensity gradient. The phase distribution of the generated light fields is also spiral shaped. We believe that the proposed diffractive element will be useful in the area of laser manipulation and laser–matter interaction.