An optical drill for the fabrication of photonic crystals

An optical drill is proposed for the nanofabrication of three-dimensional ( 3D) (diamond-like) lattices in positive photoresists, thereby opening a way towards 3D photonic crystals at optical wavelengths. Basically, an ensembl e of coherent light beams is used to produce a holographic pattern in a pho toresist of strongly nonlinear response. Multiple exposures are then perfor med for different phase shifts of one (several) of the beams. By doing this , not only are atomic bonds simulated with the spatial shift of the hologra phic pattern, but also the interconnections allow the resist development af ter exposure. An experimental demonstration is shown in a 2D case where thr ee diffracted beams originating from the same UV Ar+ laser are combined to create a triangular lattice of circular holes. Results are given for variou s phase shifts of one of the diffracted beams and for different exposure ti mes of the photoresist. The extension to the four laser beam case necessary for the fabrication of 3D structures is discussed.