Off-Axis Spiral Phase Mirrors To Create Vortex Beams


There has been an increased interest in taking advantage of the orbital angular momentum properties of light via helical wavefronts for various applications in manufacturing, imaging, and communications. By manipulating and enhancing these ‘vortex’ beams, new and more efficient applications in various industries can be realized using high powered or ultra-fast lasers. Previously, vortex beams have been generated using spiral phase plates (SPP’s), either as a transmissive in-line optical element or as a 180 degree direct backscatter mirror element. Transmissive elements can however distort the laser beam spatial and temporal profile at high powers or ultra-fast pulses due to unwanted self-phase modulation and spectral dispersion. Reflective optics at 180 degrees require additional beam switching elements (usually also transmissive), in which a small fraction of the beam can be back reflected risking damage to the laser system. These limitations have prevented the application of such spiral phase plates in high power and ultrafast laser systems to date.

Researchers at the University of Alberta have developed a cost effective, high damage threshold off axis spiral phase mirror (OASPM) to generate vortex beams in high power and ultrafast lasers. These OASPM’s, which can be manufactured using a set of discrete steps or a continuous surface, can be used in the output beam lines of high power laser systems in place of one of the turning mirrors. OASPM’s are manufactured to match any desired laser wavelength, incidence angle and diameter using standard deposition techniques. They can be coated with metal reflective coatings or high power dielectric mirror coatings for high damage threshold applications.


Figure 1: Illustration of an incident planar wave laser converting to a helically phased laser


Longman, A and Fedosejevs, R., “Mode conversion efficiency to Laguerre-Gaussian OAM modes using spiral phase optics,” Opt. Express 25, 17382-17392 (2017).


  • Low manufacturing cost by standard deposition techniques;
  • Extremely customizable to any laser system;
  • Very high conversion efficiency (up to 93%);
  • Applicable to any optical wavelength, incidence angle or beam size

Potential Markets

  • Signal multiplexing in fiber and wireless communications
  • Laser manufacturing/welding/cutting/3D printing
  • Enhanced imaging techniques
  • Atom trapping
  • Research grade high power laser facilities

Protection Status

Patent pending

Product Number


Contact Information

Shalon McFarlane
Technology Management Group
TEC Edmonton – University of Alberta
Phone: 780-492-0230