Thermo-optical Fresnel zone plates with polymer-coated patterned chromium for coma aberration correction

Abstract In optical systems, where miniaturization is the dominant trend, flat optical components capable of active aberration correction are increasingly required. SmartLens enables tunable wavefront control by locally modifying the refractive index of a transparent thermo-optic polymer using a microscale heater. However, such heaters are typically fabricated through complex multistep photolithography. In this study, we designed and simulated a Fresnel zone plate (FZP)-based microheater geometry to optimize optical efficiency and aberration control. The optimized FZP-shaped heater is fabricated by direct laser writing on a 70 nm-thick chromium (Cr) film and coated with a 1.1 mm-thick polydimethylsiloxane layer to enable thermo-optic modulation. A pronounced coma aberration was generated under off-axis conditions and subsequently compensated through electrically induced thermo-optic wavefront modulation. The fabricated SmartLens demonstrated correction of the off-axis coma aberration, which was quantitatively verified using point spread function and modulation transfer function analyses, including the reduction of directional anisotropy and the convergence of orthogonal full width at half maximum values.