Polar coordinate laser pattern generator for fabrication of diffractive optical elements with arbitrary structure

A precision laser pattern generator for writing arbitrary diffractive elements was developed as an alternative to Cartesian coordinate laser/electron-beam writers. This system allows for the fabrication of concentric continuous-relief and arbitrary binary patterns with minimum feature sizes of less than 0.6 µm and position accuracy of 0.1 µm over 300-mm substrates. Two resistless technologies of writing on chromium and on amorphous silicon films were developed and implemented. We investigated limit characteristics by writing special test structures. A 58-mm f/1.1 zone plate written directly is demonstrated at a λ/50 rms wave-front error corresponding to a 0.06-µm pattern accuracy. Several examples of fabricated diffractive elements are presented.