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Optical Fresnel zone plate flat lens: colored photoresist through I-line stepper
The specially developed color resist enables low-cost, mass-production of visible light Fresnel zone plates using only exposure and development through an i-line stepper used in the semiconductor industry.
In this study, we present a simplified method for fabricating visible Fresnel zone plate (FZP) planar lenses, a type of diffractive optical element, using an i-line stepper and a special photoresist (color resist) that only necessitates coating, exposure, and development, eliminating the need for etching or other post-processing steps. Despite the simple fabrication procedure of the presented method, these results demonstrate that each type of color-resist FZP lens is more than capable of focusing light down to approximately 1 μm, a size which typically can only be achieved by utilizing objective lenses with conventional refractive optics. Besides this point, two other factors can be identified in our experiment that contributed to such results: the non-ideal outer line width of the resist pattern in our fabricated structure and the polychromatic nature of the ultrashort pulsed light source used to evaluate the lens performance.
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