Two-Photon Direct Laser Writing of Inverse-Designed Free-Form Near-Infrared Polarization Beamsplitter

This paper presents an inverse-designed 3D-printed polymer-based broadband free-form polarization beamsplitter in the near-infrared. A computational inverse-design method is used to design a thin free-form meta-grating to split normally incident light with different polarizations to different diffraction orders, one toward the left first order and one toward the right first order. The grating is 3D-printed using two-photon direct laser writing. Polarization splitting behavior is experimentally observed in the near-infrared region for wavelengths of 1.3 and 1.55 µm, and with performance metrics close to the simulation values. The proposed platform combining inverse-design and 3D-printing can be extended to the design, fabrication, and integration of multiple broadband photonic structures to build devices with complex functionalities.