ABSTRACT
Grating lenses for optical branching were designed by introducing a phase-modulation function. The lenses have the dual functions of focusing and branching. The phase-modulation function was optimized to balance the optical intensity values for the required branchings and to suppress those for undesirable branchings. Phase-modulated grating lenses, with three and five branchings, were fabricated by using a computer and an electron-beam exposure system. The focusing and branching characteristics obtained by these lenses show excellent agreement with the theoretically predicted profiles.
ABSTRACT
An axicon optical element that utilizes a diffraction grating has been fabricated for collimating the Cerenkov radiation wave. The grating axicon has the advantage of a simple structure, which can easily be fabricated by the computerized numerical control machining technique. The collimation function of the grating axicon is confirmed for Cerenkov-type second-harmonic generation in LiNbO(3) waveguides, and correction of the aberration caused by substrate anisotropy is investigated. The aberration can be compensated by appropriately inclining either the substrate facet or the grating axicon.