Growing 2D Materials on Optical Fibers

At the university of Jena in Germany Quyet Ngo studies optical fibres functionalized by 2D materials. (Source: J. Meyer, U. Jena)

2D materials have enormous potential for a wide variety of appli­cations. For instance, combined with optical fibres, 2D materials can enable novel appli­cations in the areas of sensors, non-linear optics, and quantum technologies. However, combining these two components has so far been very laborious. Typically, the atomically thin layers had to be produced separately before being trans­ferred by hand onto the optical fibre. Together with Aus­tralian colleagues, Jena researchers have now succeeded for the first time in growing 2D materials directly on optical fibers. This approach signi­ficantly faci­litates manu­facturing of such hybrids.

“We integrated transition metal dichal­cogenides – a 2D material with excellent optical and photonic properties, which, for example, interacts strongly with light – into specially developed glass fibers,” explains Falk Eilenberger of the Univer­sity of Jena and the Fraunhofer Institute for Applied Optics and Precision Engineering (IOF) in Germany. “Unlike in the past, we did not apply the half-nanometre-thick sheet manually, but grew it directly on the fiber,” says Eilen­berger, a specialist in the field of nano­­photonics. “This improve­ment means that the 2D material can be integrated into the fiber more easily and on a large scale. We were also able to show that the light in the glass fiber strongly interacts with its coating.” The step to a practical appli­cation for the intelligent nano­material thus created is no longer very far away.

The success has been achieved thanks to a growth process developed at the Institute of Physical Chemistry of the University of Jena, which overcomes previous hurdles. “By ana­lysing and controlling the growth parameters, we iden­tified the conditions at which the 2D material can directly grow in the fibers,” says Jena 2D materials expert Andrey Turchanin, explaining the method based on chemical vapour deposition techniques. Among other things, a tempera­ture of over 700 degrees Celsius is necessary for the 2D material growth.

Despite this high temperature, the optical fibers can be used for the direct CVD growth: “The pure quartz glass that serves as the substrate withstands the high tempera­tures extremely well. It is heat-resistant up to 2,000 degrees Celsius,” says Markus A. Schmidt of the Leibniz Institute of Photonic Tech­nology, who developed the fibers. “Their small diameter and flexibility enable a variety of appli­cations,” adds Schmidt. The combination of 2D material and glass fiber has thus created an intel­ligent material platform that combines the best of both worlds. “Due to the functionalisation of the glass fiber with the 2D material, the inter­action length between light and material has now been significantly increased,” says Antony George, who is developing the manu­facturing method for the novel 2D materials together with Turchanin.

The team envisages potential applications for the newly developed materials system in two particular areas. Firstly, the materials combination is very promising for sensor technology. It could be used, for example, to detect low concen­trations of gases. To this end, a green light sent through the fiber picks up infor­mation from the environment at the fiber areas func­tionalized with the 2D material. As external influences change the fluorescent properties of the 2D material, the light changes colour and returns to a measuring device as red light. Since the fibers are very fine, sensors based on this technology might also be suitable for appli­cations in bio­technology or medicine.

Secondly, such a system could also be used as a non-linear light converter. Due to its non-linear properties, the hybrid optical fiber can be employed to convert a mono­chromatic laser light into white light for spectro­scopy appli­cations in biology and chemistry. The Jena researchers also envisage applications in the areas of quantum electronics and quantum commu­ni­cation.

The scientists involved in this development emphasise that the success of the project was primarily due to the exceptional inter­disciplinary cooperation between various research institutes in Jena. Based on the Thuringian research group “2D-Sens” and the Colla­borative Research Centre “Nonlinear Optics down to Atomic Scales” of Friedrich Schiller University, experts from the Institute of Applied Physics and Institute of Physical Chemistry of the Univer­sity of Jena; the University’s Abbe Center of Photonics; the Fraunhofer Institute for Applied Optics and Precision Engi­neering IOF; and the Leibniz Institute of Photonic Technology are colla­borating on this research, together with colleagues in Australia.

“We have brought diverse expertise to this project and we are delighted with the results achieved,” says Eilen­berger. “We are convinced that the techno­logy we have developed will further strengthen the state of Thuringia as an industrial centre with its focus on photonics and opto­electronics,” adds Turchanin. A patent appli­ca­tion for the inter­disciplinary team’s invention has recently been filed. (Source: U. Jena)

Reference: G. Q. Ngo et al.: Scalable functionalization of optical fibers using atomically thin semiconductors, Adv. Mat., online 6 October 2020; DOI: 10.1002/adma.202003826

Link: Institute of Applied Physics, Abbe Center of Photonics, Friedrich Schiller University, Jena, Germany

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