Figure 6

A large-scale POPA that is fabricated and experimentally characterized. (a) Image of the fabricated sample under microscopy showing the excitation via a fiber. (b) SEM images of the fabricated sample. (c) Measured (left one) and theoretically calculated (right one) far-field power emission patterns at 1540 nm. Both figures share the same coordinate ranges in the u-v space (u = sin(θ)cos(φ), v = sin(θ)sin(φ)), i.e. v from −0.283 to 0.283, u from −0.203 to 0.2205. (d) Measured and theoretically calculated far-field power profiles along the reference line 1 at various wavelengths, indicating a clear scanning behavior. (e) Measured and theoretically calculated power profiles along the reference line 2 at 1540 nm. The inset shows the theoretically calculated directivity of the fabricated POPA. The results in (c,d and e) are obtained under the quadratic phase distribution of φ _n with a = −0.125 (Supplementary Information Section 8).