Fabrication of fine metal structures based on laser drawing method using interference pattern from co-propagating optical vortices

We propose and demonstrate a photolithography method for fine metal structure fabrication based on laser drawing that uses the interference pattern generated by co-propagating optical vortices. A tiny dark core region of the optical vortex allows us to overcome the diffraction limit for Gaussian beams. This means that the proposed method can be used to fabricate finer structures than those produced by the conventional laser drawing method while using a Gaussian beam, even under low numerical aperture conditions. The feasibility of the proposed method was demonstrated experimentally using a system that included an axially symmetrical polarization element that can generate the co-propagating optical vortices using a common path optical system. Our method has potential to fabricate few tens of nanometer scale metal line structures by increasing numerical aperture conditions and should be applicable to the development of nanometer scale electronic and optical devices and structures, such as integrated circuits and metamaterials, without using electron beam lithography.