Circular grating, a.k.a flat axicon, is a space-variant retarder that transforms Gaussian beam into a Bessel-Gauss beam.
Circular grating | flat axicon is leading for its high damage threshold, comparing to alternative devices. It has laser irradiation resistance similar to uncoated fused silica substrates.
The structure of the element is unique due to formation birefringent nanograting’s inside a bulk of fused silica glass, sensitive to the incident polarization.
Circular grating can generate both – positive and negative Bessel-Gauss zones, separately with LHCP and RHCP polarizations. Also, positive and negative zones simultaneously with linear polarization. The working regime depends only on incident polarization.