Femtosecond Laser Non‐Diffracting‐Beam Lithography via Phase Modulation for Dielectric Metasurface Fabrication

Abstract

ABSTRACT Dielectric phase‐change metasurfaces enable programmable light control and show great application potential in optoelectronics. However, current technologies are limited by challenges in achieving high‐uniformity, high‐precision fabrication over large areas, as well as selective phase‐state modulation of individual meta‐atoms. To address these challenges, a femtosecond (fs)‐laser phase‐modulated non‐diffracting‐beam lithography (PNDL) technique is proposed. By superimposing axicon and blazed grating phases, the fs‐laser beam is shaped into a quasi‐Bessel non‐diffracting‐beam with a depth of focus over 10 times greater than that of a tightly focused Gaussian beam, thereby reducing the need for refocusing and minimizing focal drift. The dynamic beam deflection during fabrication can be controlled with 7 nm precision. The voxel metasurfaces composed of phase‐change regions are then chemically processed to achieve maskless lithography. PNDL is used to fabricate a tunable Ge 2 Sb 2 Te 5 metasurface with a structural feature size of 9 nm. Furthermore, multifunctional programmable photonic logic devices are fabricated and modulated, demonstrating high‐precision capabilities. This approach provides a novel paradigm for active metasurface fabrication and modulation, laying the foundation for next‐generation photonic devices.