Direct laser writing of tunable diffractive micro-optics on graphene oxide film

Lee, Hyub; Low, Mun Ji; Lim, C. H.; Murukeshan, Vadakke Matham; Kim, Young‐Jin

doi:10.1117/12.2289573

Cited by 2 publications

(8 citation statements)

References 12 publications

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“…Efficiency-Enhanced FZP. For typical GO/rGObased FZPs, 14,20 which are manufactured via single-exposure fs-laser writing, there should be a trade-off between focusing efficiency and resolution. The focusing efficiency and resolution can be improved by elevating the transmission contrast between adjacent binary zones and reducing feature size, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…6,15,19,20 However, the abovementioned concurrent variation in the degree of photoreduction and the patterning linewidth of GO/rGO leads to a trade-off between focusing resolution and efficiency. 14,15 It is known that focusing efficiency and resolution can be enhanced by attaining a distinct transmission discrepancy between adjacent binary zones and narrowing the width of the outermost zone, respectively. The radical transmission contrast generated by a high degree of photoreduction of GO contrasts with the minimum patterning linewidth under the lowest extent of photoreduction.…”

Section: Introductionmentioning

confidence: 99%

“…The radical transmission contrast generated by a high degree of photoreduction of GO contrasts with the minimum patterning linewidth under the lowest extent of photoreduction. [12][13][14][15]20 In particular, it seems rather challenging to overcome such a trade-off. For instance, although both focusing efficiency and focusing resolution are improved by applying the Rayleigh−Sommerfeld diffraction theory, 21 the trade-off between focusing resolution and efficiency still exists in the optimized lens.…”

Section: Introductionmentioning

confidence: 99%

“…Femtosecond laser (fs-laser)-induced micro/nanopatterning of reduced graphene oxide (rGO), accompanying in situ photoreductions, has garnered considerable attention because its properties can be effectively adjusted using a facile and maskless method. − GO/rGO-based micro/nanostructures with mechanical flexibility, chemical/physical stability, and optical and electrical property tunability have been used in various applications, such as diffractive lenses, supercapacitors, photodetectors, and actuators. ,− With the removal of oxygen and carbon atoms, the patterning linewidth and photoreduction degree of GO/rGO are adjustable by controlling the fs-laser parameters encompassing the pulse energy and repetition rate. ,− At present, the most adopted technology for the photoreduction of GO via an fs-laser is direct writing based on a single-exposure process . However, when this method is used for enhancing the photoreduction degrees of GO/rGO, the side effect of the corresponding patterning linewidth widening becomes too obvious to be ignored. − The co-occurrence of tailoring the patterning linewidth and degrees of photoreduction hinders the application of fs-laser-induced GO/rGO patterning. ,− When the desired optical transmission, film thickness, and electrical conductivity come from high or medium degrees of GO/rGO photoreduction, it is unreasonable to expect to employ the minimum linewidth that can only be achievable at the lowest degree of photoreduction. Thus, the feature sizes of micro/nanodevices may be much larger than the minimum linewidth, when device performances are strongly subject to the optical and electrical properties of GO/rGO.…”

Section: Introductionmentioning

confidence: 99%

“…However, an optical absorption may not be flexibly controlled independently of the miniaturization of a patterning linewidth, which requires a low degree of photoreduction. Regarding optical lenses, the desired degree of photoreduction is diversified because the optical transmittance, refractive index, and film thickness of GO/rGO are strictly determined according to their design criteria. ,,, The contradiction about the photoreduction and linewidth still exists for this kind of application, considering that all the properties of GO/rGO, including the minimum patterning linewidth, can only be adjusted synchronously as a whole. For GO/rGO-based devices that rely on the fs-laser single-exposure process, the performance can only be ameliorated at the expense of feature size because the minimum patterning linewidth of GO/rGO cannot be maintained as photoreduction deviates from its lowest level.…”

Section: Introductionmentioning

confidence: 99%

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Photoreduction-Insensitive GO/rGO Patterning Based on Multistep Femtosecond Laser Writing for Implementing Fresnel Zone Plates

Jiang

Park

Lee

et al. 2021

ACS Appl. Nano Mater.

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As boosting the degree of photoreduction widens a patterning linewidth, devices comprising femtosecond laser (fs-laser)induced reduced graphene oxide (rGO) present the dilemma of a choice between optimum performance and miniaturization. Here, by exploiting multistep fs-laser writing with a low repetition rate, photoreductioninsensitive GO/rGO patterning is realized, which exhibits a photoreduction-insensitive and constant patterning linewidth at arbitrary stages of the evolving photoreduction process. During a photoreductioninsensitive patterning, a GO film is exposed iteratively to the same fslaser beam to achieve targeted photoreduction levels, while the minimum patterning linewidth is preserved under a fixed pulse energy. The proposed patterning approach that results from preventing a thermal accumulation and roughening a GO/rGO surface achieves an optimizable device performance, without compromising on the feature size. In particular, a photoreduction-insensitive patterning provides a high optical transmission contrast while preserving a minimum linewidth. When two Fresnel zone plates that involve binary zones comprising GO/rGO are fabricated via single-exposure and multistep fs-laser-writing methods, respectively, the latter patterning approach provides a 3.9-fold enhancement of focusing efficiency compared with the former. Consequently, the demonstrated photoreduction-insensitive patterning approach confirms the feasibility of maintaining a patterning linewidth while tailoring the photoreduction levels of GO/rGO, thus promoting the development of GO/rGO-related micro/nanodevices.

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Section: Resultsmentioning

confidence: 99%