Femtosecond Laser Processing Technology for Anti-Reflection Surfaces of Hard Materials

Abstract

The anti-reflection properties of hard material surfaces are of great significance in the fields of infrared imaging, optoelectronic devices, and aerospace. Femtosecond laser processing has drawn a lot of attentions in the field of optics as an innovative, efficient, and green micro-nano processing method. The anti-reflection surface prepared on hard materials by femtosecond laser processing technology has good anti-reflection properties under a broad spectrum with all angles, effectively suppresses reflection, and improves light transmittance/absorption. In this review, the recent advances on femtosecond laser processing of anti-reflection surfaces on hard materials are summarized. The principle of anti-reflection structure and the selection of anti-reflection materials in different applications are elaborated upon. Finally, the limitations and challenges of the current anti-reflection surface are discussed, and the future development trend of the anti-reflection surface are prospected.

Keywords: anti-reflection; biomimetic structures; femtosecond laser processing; hard materials; micro/nanostructures.

Figure 1

Schematic diagram of multilayer graded index of refraction for a single inverted cone structure and effective index for different vertical distances x, (a) Top view and (b) longitudinal section [61], Copyright © 2016 Elsevier.

Figure 2

(a) Topping view and (b) Crossing sectional view of the inverted cone-shaped structure arrays with a period of 90 μm on a high-resistance silicon substrate by SEM; (c) Time-domaining signal and (d) Frequency-domaining spectrum of inverted conical structure sample [61], Copyright © 2016 Elsevier.

Figure 3

(a) Laser ablation kinetics of micro/nanostructure growth paths and deposition on silicon substrates; (b) Schematic diagram of round dot laser cleaning oxide deposition; (c) Reflectance spectra of textured silicon surfaces in the range of 300–2500 nm; (d) Reflection spectra of micro/nano-construction fabricated by laser cleaning assisted laser ablation irradiation and unprocessed silicon within MIR region (2.5–16 μm) [89], Copyright © 2020 Elsevier.

Figure 4

(a) The synergetic fabrication process of the urchin-like array; (b) SEM images regarding morphological features of urchin-like arrays and individual urchin-like structures; (c) Anti-reflection performance of micro/nanostructures in VIS, UV, and IR bands [105], Copyright © 2020 Elsevier.

Figure 5

(a) The schematic diagram of femtosecond laser modification along with subsequent wet etching of sapphire with and without a sacrificial layer; (b) Optical photograph, (c) LSCM image and (d) local SEM image of the moth eye; (e) Schematic diagram of preparation process of anti-reflection sapphire surface for bionic moth eye; (f–h) SEM images of the bionic moth-eye structures on sapphire; (i) Experimentally measured transmittance of one-sided and two-sided processed sapphire in the mid-infrared band; (j) The relationship between transmittance and incident angle of sapphire with anti-reflection structures on both sides [75], Copyright © 2022 Springer Nature.

Figure 6

SEM images (a) top view and (b) cross-sectional view of a 2D laser-induced periodic surface structure with deep subwavelength periodicity on the diamond surface; (c) Reflectance spectrum of the diamond sample; (d) Absorptivity spectrum of the diamond sample [133], Copyright © 2021, American Chemical Society.