Super-Collimation by Circular Grating near Mirror

We investigate numerically and experimentally the far field effects of a transmissive circular grating placed near mirror and demonstrate: (i) a strong enhancement of axial components of reflected laser beam (effect of super-collimation) at double- and multi-diffraction on circular grating outside and inside Fabry-Perot cavity (passive case), (ii) increasing brightness and beam quality of microlaser due to the circular grating next to one of the mirrors of the laser cavity (active case).