Diffractive optical elements: design and fabrication at TASC-INFM

Diffractive optical elements (DOE's) can be used to manipulate the amplitude, the phase and the polarization of light beams. They can operate over a wide range of wavelength from UV to X ray radiation. Interest in DOE's has grown rapidly in recent years since they are smaller and lower in size and weight than conventional optical elements and in addition allow optical functions impossible to reach with other refractive or reflective optical elements. In this paper we report results obtained in DOE's design and fabrication at the LILIT Nanolithography beam line developed at the national laboratory TASC-INFM, Among the design methods we have used, the phase retrieval iterative algorithm approach is presented in more detail here. There are also presented aspects involved in the fabrication of high resolution zone plates for focusing soft X-rays. The fabrication process is based on e-beam lithography and etching techniques similar to those used in the microelectronic technology, allowing structures sized down to few tens of nanometers. Experimental results are presented for some applications of our DOE's: laser beam shaping, optical tweezers array generation and X-ray microscopy.