Broad-Band Ultra-Low-Reflectivity Multiscale Micro–Nano Structures by the Combination of Femtosecond Laser Ablation and In Situ Deposition

Abstract

Functional surfaces with broad-band ultralow optical reflection have many potential applications in areas like national defense and energy conversion. For efficient, high-quality manufacturing of material surfaces with antireflection features, a novel machining method for multiscale micro–nano structures is proposed. This method can enable the collaborative manufacturing of both microstructures via laser ablation and micro–nano structures with high porosity via in situ deposition, and it can simplify the fabrication process of multiscale micro–nano structures. As a result, substantially improved antireflection properties of the treated material surface can be realized by optimizing light trapping of the microstructures and enhancing the effective medium effect for the micro–nano structures with high porosity. In ultraviolet–visible–near-infrared regions, average reflectances, as low as 2.21 and 3.33%, are achieved for Si and Cu surfaces, respectively. Furthermore, the antireflection effect of the treated surface can also be extended to the mid-infrared wavelength range, where the average reflectances for the Si and Cu surfaces decrease to 5.28 and 5.18%, respectively. This novel collaborative manufacturing method is both simple and adaptable for different materials, which opens new doors for the preparation of broad-band ultra-low-reflectivity materials.

Laser processing of micro/nano biomimetic structures

“…Cardoso et al [60] mimicked the lotus, used nano-and picosecond laser ablated micro cell and submicrostructure on cell respectively which achieved superhydrophobic surface with a contact angle of 161.5 • ±3 • . Chen et al [61] used femtosecond laser fabricated micro grooves accompanied by in situ deposition which formed porosity.…”

Hierarchical platinum–iridium neural electrodes structured by femtosecond laser for superwicking interface and superior charge storage capacity

“…However, under highly overlapped scanning, further increasing E and N simultaneously might result in too much stack, which blocks the already formed structures. An example of this is the complete disappearance of scanning traces in the SEM of Overlap 2 [37]. Therefore, it is clear that in this scenario, the CSC tends to decrease.…”

“…Therefore, higher CSC is obtained. Increasing both E and N leads to intense ablation with more micro-protrusions and nanoparticles in microgrooves, evident under interval scanning [36][37][38], and also increases CSC. However, under highly overlapped scanning, further increasing E and N simultaneously might result in too much stack, which blocks the already formed structures.…”

“…This is in agreement with the SEM results, which indicate the presence of enriched micro-protrusions and nanoparticles. With regard to processing parameters, increased φ line leads to denser structures due to decreased Δx [36,37]. Therefore, higher CSC is obtained.…”

Direct Writing of Silicon Oxide Nanopatterns Using Photonic Nanojets

“…The contemporary femtosecond laser treatment of silicon surfaces is focused primarily on removing material using an energy higher than that required for silicon ablation threshold to ablate the material in the processing area. Ablation technology can be used to alter surface reflectivity [11,12] and wettability [13,14] as well as manufacture micro-lens arrays [15,16]. Moreover, owing to the heat accumulation effect, femtosecond lasers with high repetition rates can directly pattern silicon oxide patterns on a silicon substrate, which has potential applications in maskless lithography [17] and microfluidics [18].…”