Diffractive optical elements for optical identification

We present the design and fabrication of diffractive optical elements for optical identification purposes. Two methods for optical identification are discussed. In this feasibility study, approaches using one and two binary reflective diffraction gratings are demonstrated. The diffraction orders of the grating/gratings are used as a binary code for optical identification. The gratings are designed using the iterative Fourier transform algorithm for an incoming coherent monochromatic laser beam (633 nm, He-Ne laser). The microrelief structures are fabricated by a combination of atomic layer deposition and electron beam lithography. The scanning electron microscope images show good quality of diffraction gratings. Optical characterization and measurement results demonstrate the feasibility of the proposed identification methods.