Light Coupling Devices for Subwavelength Waveguides Based on Second-Order Surfaces, Fabricated by Two-Photon Laser Lithography

Light input/output devices are essential for coupling between bulk and bre optics devices and photonic integrated circuits (PICs). In this work, broadband couplers for optical waveguides lifted from the surface were fabricated using two-photon laser lithography, and comparison with numerical modelling was carried out. It was demonstrated experimentally that the ellipsoid-based coupler is optimal for coupling light into the waveguide. The average transmittance of a system comprising two adapters in the spectral range 700-1000 nm for s-polarised radiation amounted to at least 27%.