Far‐Field Polarization Engineering from Nonlinear Nanoresonators

Nanoresonators fabricated from low-loss dielectrics with second-order nonlinearity have emerged as a widespread platform for nonlinear frequency conversion at the nanoscale. However, persisting challenge in this research is generated complex far-field polarization state of upconverted light, which limiting factor many applications. It will be highly desirable to generate uniform states across all propagation directions, control truly along optical axis and simultaneously able tune entire circumference Poincaré sphere by solely modifying excitation polarization. Here, nanoresonator combining these properties theoretically proposed experimentally demonstrated. At first, an analytical model connecting induced multipolar content desired derived. Based on this, dielectric designed enable sum-frequency generation (SFG) pure tuneable states. In experiment, nanoresonators III-V semiconductor gallium arsenide (110)-orientation are excited SFG scheme individually controllable beams. The demonstrated back-focal plane measurements Stokes polarimetry.