3D-printed facet-attached optical elements for beam shaping in optical phased arrays

We demonstrate an optical phased-array equipped with a 3D-printed facet-attached element for shaping and deflection of the emitted beam. The beam shaper combines freeform refractive surfaces with total-internal-reflection mirrors and is in-situ printed to edge-emitting waveguide facets using high-resolution multi-photon lithography, thereby ensuring precise alignment with respect to on-chip waveguide structures. In a proof-of-concept experiment, we achieve a grating-lobe free steering range of $\pm$30$^{\circ}$ and a full-width-half-maximum beam divergence of approximately 2$^{\circ}$. The concept opens an attractive alternative to currently used grating structures and is applicable to a wide range of integration platforms.