All‐Glass Nanohole Metalens by Non‐Diffracting Laser Lithography

Abstract

Traditional nanopillar metalenses are usually confronted with problems of limited phase delay due to restricted aspect ratio and duty cycle of structural units. A new design and ultrafast laser fabrication method of an all‐glass nanohole metasurface is proposed. High‐aspect‐ratio nanoholes with subwavelength periods, tunable depths, and fixed duty cycle function as phase shift units, realizing idealized linear 2π phase delay to support great light modulation performance. A non‐diffracting laser lithography approach is developed to fabricate nanohole arrays, using a unique Bessel beam modulated by a reversed‐axicon phase diagram to guarantee hole diameter consistency along the depth. Combining with thermal annealing and chemical etching, surface and subsurface damage‐free nanohole arrays are produced with periods down to 800 and precisely controlled depths over 10 µm. The capability helps realize the rapid fabrication of a high‐performance all‐glass nanohole metalens with ≈97% modulation efficiency at 1.55 µm. A large 2 cm‐diameter metalens and diverse optical devices like axicon, vortex wave plate, and blazed grating are also demonstrated. The study provides a new avenue of all‐glass metalens, and makes custom metalens more economical and easily accessible.