High efficiency fast diffractive lens for beam coupling

Diffractive lenses for laser diode beam focusing collimating and coupling have wide applications. Large numerical aperture and high light efficiency are important issues for the coupling lenses. Numerical aperture of a typical laser diode beam can be as large as NA ~ 0.5. To capture the highly divergent beam the lens must have a low F-number of F/1 ~ F/2. Coupling the laser beam into an optic fiber with an acceptance angle of NA ~ 0.1 - 0.2 needs even larger numerical aperture of the lens.