Two-level binary diffractive optical elements for symmetric line-patterns generation from laser diodes

Abstract

Numerous tasks of laser pointing, visual adjustment, targeting and laser radar require shaping of laser diode beam into the line contour patterns. The examples of the line patterns are straight-line segment, cross, contour of rectangle, system of points. One more task is to circularize the elliptical beam that is typical for laser diodes even after passing through standard collimators. The traditional approach is either to use cylindrical lenses1 or to apply computer-generated phase holograms reconstructing the system of points2. The usual problem in computer-generated holograms is the dot-type structure of the image, limited possibilities to achieve uniform intensity distribution along lines. Patterns containing several lines can be formed by faceted diffractive optical elements (DOEs), which use some part of clear aperture for line segment generation. However splitting the aperture adds problems in line uniformity, width, interference between lines. Other way is to use multi-channel DOEs3 utilizing several diffraction orders of DOE at once. We propose a special way to generate symmetrical patterns based on the full use of symmetrical diffraction orders of binary diffraction grating. Full cycle of design, computer simulation, fabrication and experimental investigation of DOEs for laser diodes is described in this report.