Investigating the Production of Gradient Index Optics by Modulating Two-Photon Polymerisation Fabrication Parameters

Two-photon polymerisation (TPP) is an additive manufacturing technique allowing the fabrication of arbitrary 3D geometries with sub-micron features. As such, TPP is a promising technique for fabricating optical metamaterials. The electromagnetic (EM) properties of metamaterials arise from their geometrical structure rather than their material constituents alone. By introducing variations across the unit cells of a metamaterial spatially varying EM properties can be created. In this way, gradient index (GRIN) optics can be produced which are useful for reducing coupling losses and creating compact optical systems. This work looks at modulating fabrication parameters to achieve geometrical variations. Line widths of IP-L 780 are measured on an array of lines fabricated at different laser powers and scan speeds. Proof of concept woodpile structures are also fabricated where laser power is changed for individual lines in the structure resulting in geometrical changes. Changing fabrication parameters along a single scan line is also investigated.