Vortex Generation and Pixel Calibration Using a Spatial Light Modulator for Maskless Lithography

We present aerial images demonstrating the generation of an isolated optical vortex via and its through-focus characteristics using a SLM (spatial light modulator) for optical maskless lithography. Aerial images show that a 4 phase step vortex can be formed by a group of 2 x 2 pixels. The vortex showed that there is minimal through-focus drift in the intensity profile whereas an isolated feature generated without a phase singularity showed noticeable drift of the profile. We also present experimental results in utilizing a method to improve the sensitivity in pixel calibration for an optical maskless lithography system. Using an optimized configuration of the surrounding mirrors, the calibration sensitivity of the pixel under test can be increased and even maximized at a certain defocus. The calibration sensitivity is improved by ~1.8x for our surrounding mirror configuration without defocus.