Fabrication of 3D photonic structures

Abstract

This paper reports first results of a method for the fabrication of 3D photonic structures consisting of “bubbles” within a polymer matrix. A multi-layer resist is exposed with electron-beam lithography, and then developed to form “bubbles” in an underlayer. The layer with “bubbles” is stabilized, another layer is deposited, and a new set of “bubbles” is created after alignment. The advantage of the method is that it allows control of bubble positions with the accuracy of electron-beam lithography, control of the bubble size (0.2–5 μm), fabrication of 3D structures (structures more than 10 μm thick with more than 10 layers were fabricated), creation of bubbles of various shapes (disks, ellipsoids, squares, triangles, etc.), and production of photonic crystals with composite cells. Moreover, aperiodic (almost arbitrary) structures can be fabricated, so that arbitrary refractive index distribution could be arranged in 3D space. Optical experiments were made to study light transmission through a 3D photon crystal. A fcc crystal consisting of five layers was used. Light transmission was measured normal to the crystal and the results obtained agreed with those expected for a photon crystal of this thickness.