Fast preparation method for spiral phase plates based on digital grayscale mask

Abstract

The wide application of spiral phase plate has promoted the rapid development of its production technology. Traditional spiral phase plate fabrication techniques such as electron beam lithography, focused ion beam lithography, laser direct writing have the disadvantages of high cost and low efficiency due to expensive equipment and point-by-point exposure. In this paper, we propose a fast preparation method for spiral phase plates based on digital grayscale mask. The 3D contours of the spiral phase plate are mapped into a grayscale mask by interval quantization, and the criteria for interval quantization are explored in detail. For the continuous spiral phase plate and step spiral phase plate, gray scale continuous digital mask and gray scale step digital mask are designed and used for digital lithography respectively, and the experimental results are tested and analyzed. The results show that spiral phase plates with different topological charges for specific wavelength can be fabricated by controlling the gray-scale digital mask. The fabricated spiral phase plates have smooth surfaces with well-defined edge contours and are capable of initially modulating the laser beam.