Armored Nanocones Engraved by Selective Laser Doping Enhanced Plasma Etching for Robust Supertransmissivity.

Abstract

Optical antireflection surfaces equipped with subwavelength nanocone arrays are commonly used to reach broadband supertransmissivity but are limited by the lack of wear resistance. We design and manufacture a structured surface with robust antireflection structures (R-ARS) composed of substrate-engraved nanocone arrays with micro-grid-shaped walls as protective armor. An ultrafast laser beam is used to selectively ablate and dope the metal from the deposited film into the subsurface of optical substrates to strengthen self-assembled nanoparticles formed during plasma etching as masks for nanocones. The untreated microscale metal grids serve as etching masks for the remaining protective armor. The geometrical features of nanocones and spatial distribution of protective armor with a proper duty cycle are theoretically optimized for improvement in both transmissivity and mechanical robustness. We demonstrate armored dense engraved nanocone arrays (with tip diameters of ∼50 nm and heights of ∼0.8 μm) on visible fused silica and infrared semi-insulating SiC with protective micro-square-grid armor. The average transmittances are improved from 93% to over 97% (on 0.4-1.2 μm) for double-face-structured fused silica, and from 60 to 65% (on 3-5 μm) for single-face-structured SiC, with few reductions of fused silica after 150 cycles of severe abrasion (under a pressure of 5.34 MPa) proving the excellent mechanical robust performance of R-ARS.