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IDENTIFYING NEW MATERIALS FOR NEXT GENERATION FIBRE OPTICS
The ongoing transition to 5G wireless technology and high-performing phone networks, along with the growing use of high-definition data by internet and cellular providers, necessitates the development of higher capacity optical fibers that are robust, durable, and lightweight.
Most telephone networks, internet connections, and cable television transmissions in use today rely on silicabased fiber-optic cables. The fibers in fiber optics are essentially transparent and flexible strands of silica glass through which light can travel. Bundled together and covered with cladding and multiple plastic and metal sheaths for protection, these fiber-optic strands serve as the waveguide through which pulses of infrared light containing information are rapidly conveyed, enabling the transmission of high-throughput data.
However, as the rate of wireless data transfer has increased and become denser, this method of transmitting data has begun to falter. The discovery and development of new optic materials is needed to take the place of silica-based fiberoptic cables to ensure we can continue to meet our progressing wireless data transmission needs.
In response to this need, a research team based at New York University Abu Dhabi’s (NYUAD) Smart Materials Lab has explored whether the properties of an organic crystal are compatible with the requirements for advanced fiber optics. Specifically, they sought to analyze the optical and other physical assets and mechanical properties of a crystalline amino acid known as L-threonine. They confirmed that they are compatible with the requirements for transduction of light over a short distance.
Dr. Pance Naumov, Professor of Chemistry and Principal Investigator at the Smart Materials Lab, NYUAD
“Realizing that silica fibers may not be the most optimal solution, particularly in view of their significant weight and a high degree of purity required for efficient transfer of information, we decided to investigate a completely different class of materials for the same purpose. Instead of silica, we used small crystals of organic materials, specifically the amino acid L-threonine, which is known to be among the stiffest known organic crystals. This mechanical robustness is important to be able to handle these crystals and to prevent damage by abrasion when they are incorporated into optical devices,” explained Dr. Pance Naumov, Professor of Chemistry and Principal Investigator at the Smart Materials Lab, NYUAD.
From NYUAD, he worked with research scientist Dr. Durga Prasad Karothu, postdoctoral associate Dr. Ghada Dushaq, research scientist Dr. Ejaz Ahmed, postdoctoral associate Dr. Srujana Polavaram, undergraduate student Rodrigo Ferreira, and research instrumentation scientist Dr. Liang Li, as well as former NYUAD postdoctoral associate Dr. Luca Catalano, Khalifa University Assistant Professor of Chemistry Dr. Sharmarke Mohamed, and NYUAD Associate Professor of Electrical and Computer Engineering Dr. Mahmoud Rasras.
To test L-threonine’s potential as a fiberoptic material, the team grew single crystals of L-threonine as elongated prisms of around 10mm in length, with a cross section of around 5mm2. The single crystals were colorless, clear, and free of visible defects, to ensure optimal light transmission without optical losses.
INSTEAD OF SILICA, WE USED SMALL CRYSTALS OF ORGANIC MATERIALS, SPECIFICALLY THE AMINO ACID L-THREONINE, WHICH ARE KNOWN TO BE AMONG THE STIFFEST KNOWN ORGANIC CRYSTALS. THIS MECHANICAL ROBUSTNESS IS IMPORTANT TO BE ABLE TO HANDLE THESE CRYSTALS AND TO PREVENT DAMAGE BY ABRASION WHEN THEY ARE INCORPORATED INTO OPTICAL DEVICES.
-Dr. Pance Naumov. Professor of Chemistry and Principal Investigator Smart Materials Lab, New York University Abu Dhabi
“Single crystals of small organic compounds have been recently considered viable candidates for applications in optics, and this area has been actively researched in the past several years. The studies have focused on the demonstration of passive (transmission of unaltered input light) and active (transmission of fluorescence) transduction of visible light. However, most of the previous studies focused on transduction of visible light. In our research, we used near-infrared light, which is important because it is the light used to transfer information in the telecommunications systems,” Dr. Naumov explained.
The research team conducted a characterization analysis of the tiny crystalline prisms of L-threonine that they had developed, looking at stiffness, hardness, and other mechanical properties. The L-threonine fibers’ functionality was also tested, including analysis of its broadband response, optical waveguiding properties, and optical losses. The researchers said their project provided the first demonstration of an organic crystal that conveys light in the near-infrared region with very low optical loss. Their work found that the amino acid L-threonine was mechanically robust and photochemically and thermally stable up to 490 Kelvin.
THE TEAM’S WORK PROVIDES A STARTING POINT FOR SIMPLE ORGANIC CRYSTALS OF STIFF MATERIALS TO BE DEVELOPED INTO CHEAP AND ACCESSIBLE FIBER- OPTIC MATERIALS
“These values provide evidence that the optical signals are transduced unaltered through the crystal. The result is promising for integration of this prototypical material in optical communication devices and fiber-optic cables operating in the O band and the C band of the spectrum,” the researchers wrote in a paper on the project recently published in the journal Nature Communications.
This high functionality in the wavelength bands of O and C are considered important for the telecommunications industry, as the standard silica fibers also have low optical losses in those bands. To simplify, they showed that when L-threonine was used for fiber-optic transmission of light, the light coming in from one end of the crystal was transmitted without alteration to the other end of the crystal, and with minimal bandwidth losses.
Dr. Naumov said the team’s work provides a starting point for simple organic crystals of stiff materials to be developed into cheap and accessible fiber-optic materials. The researchers are now advancing their work, focusing on maintaining control over the process of light conveyance through the cable and the output.
