3D Super-Resolution Using a Phase Mask Fabricated via Grey-Level Lithography

Three dimensional (3D) super-resolution can be achieved in microscopy instruments by means of phase masks that shape the point spread function [1]. Grey level lithography is an attractive procedure for the generation of these phase masks. The photolithographic phase masks (PPM) encode the light emitted from a specimen via a topographical index of refraction variation consisting of a series of phase-singularities [2]. In our case, the mask produces a double helix point-spread function (DH-PSF), which allows for the estimation of the object position throughout the depth of focus of a typical system [3]. The goal of this project was to develop processes to fabricate and characterize PPMs. We manipulated the grey-scale lithography capabilities of a maskless lithography system by priming the photoresist with multiple exposures prior to the final exposure pattern. This procedure allowed us to produce the desired topography expressed by the photoresist after exposure and development (with feature sizes on the order of 10-6m). Upon testing these phase masks in an optical system, we were able to observe the desired DH-PSF. Currently, experiments are being done to translate the fabricated topography of the photoresist into quartz through reactive ion etching. Introduction: 3D Super-Resolution Using a Phase Mask Fabricated via Grey-Level Lithography