Fast fabrication of silver helical metamaterial with single-exposure femtosecond laser photoreduction

• Main Authors: Liu Lipu, Yang Dong, Wan Weiping, Yang Hong, Gong Qihuang, Li Yan
• Format: Article
• Language: English
• Published: De Gruyter 2019-05-01
• Series: Nanophotonics
• Subjects: metallic helical metamaterial; optical chirality; single-exposure; femtosecond laser photoreduction
• Online Access: https://doi.org/10.1515/nanoph-2019-0079

Metallic helical metamaterials have become the prominent candidates for circular polarizers and other optical-chiral devices as they exhibit strong circular dichroism at a broad operation bandwidth. However, the rapid fabrication of an intertwined double helix with multiple pitch numbers and excellent mechanical strength, electrical conductivity and surface smoothness remains a challenge. We propose and realize the single-exposure femtosecond laser photoreduction of a freestanding, three-dimensional silver double-helix microstructure by the double-helix focal field intensity engineered with a spatial light modulator. At the same time, the photoreduction solution and the laser repetition rate are optimized to further tackle the surface roughness and the thermal flow problems. As a result, the silver double-helix array with the enhanced quality exhibits pronounced optical chirality in a wide wavelength range from 3.5 to 8.5 μm. This technique paves a novel way to easily and rapidly fabricate metallic metamaterials for chiro-optical devices in the mid-infrared regime.