Laser-induced reduced-graphene-oxide micro-optics patterned by femtosecond laser direct writing

• Published in: Applied surface science Vol. 526; p. 146647
• Main Authors: Low, Mun Ji, Lee, Hyub, Lim, Chin Huat Joel, Suchand Sandeep, C.S., Murukeshan, Vadakke Matham, Kim, Seung-Woo, Kim, Young-Jin
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2020
• Subjects: Diffractive micro-optics; Femtosecond laser direct writing; Fresnel zone plate; Graphene oxides; Reduced graphene oxide; Fresnel zone plate; Diffractive micro-optics; Femtosecond laser direct writing; Reduced graphene oxide; Graphene oxides
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2020.146647

[Display omitted] •Ultra-thin diffractive optics based on GO/rGO patterned by fs laser-direct-writing.•Patterning based on broad parametric tuning of a mode-locked fs pulse laser.•Qualitative and quantitative analysis of photon-material interaction for optics.•Patterning of four different types of ultra-thin GO/rGO diffractive optics.•Evaluation of optical performances of printed ultra-thin GO/rGO diffractive optics. Direct laser writing has emerged as a promising technology for facile and cost-effective single-step manufacturing of laser-induced reduced-graphene-oxide (LIRGO). Since LIRGO’s optical properties can be controlled during photoreduction process, laser-patterned micro-optics can work as light-weight diffractive optical elements over conventional bulk refractive optics. Here, we present ultra-thin diffractive LIRGO micro-optics patterned by femtosecond laser direct writing (FsLDW) with high spatial resolution and wide design flexibility based on the wide parametric tunability of femtosecond pulsed lasers over conventional continuous-wave or long-pulsed lasers. By extensive parametric control of average power (10–120 mW), pulse repetition rate (1–500 kHz) and scan speed (1–100 mm/s) in FsLDW, ultra-thin micro-optics were patterned at three patterning regimes: non-thermal photoreduction regime, thermal photoreduction regime, and ablation regime. The optical performances of Fresnel zone plates (FZP) fabricated under the three regimes were evaluated and compared; the results were 0.7%, 2.4%, and 3.8% for focusing efficiency, 12.2 µm, 13.2 µm, and 12 µm for focal spot size, 1.39 mm, 1.89 mm, and 1.77 mm for depth-of-focus for FZPs designed to 15 mm focal length with 10 concentric rings. This fabrication technique provides wide design flexibility to various planar LIRGO micro-optics for microfluidics, lab-on-a-chip, skin-attachable biomedical imaging, and micro photonic devices.