Functional facets for nonlinear crystals

We report on a new optical device allowing to efficiently add desired functionalities to a nonlinear interaction. This is achieved by focused ion beam patterning of a nano-layer of gold sputtered at the exit facet of a nonlinear crystal. The functionality is experimentally demonstrated with three examples: spatial filtering where a fundamental beam with a poor mode quality and its' frequency-doubled beam are filtered thereby providing high mode quality beams, focusing of a generated second harmonic beam and beam shaping where a fundamental Gaussian beam is transformed into any arbitrary desired frequency-doubled beam. For the latter two examples, the functional facet also provides angular separation of the fundamental and second harmonic beams.