Researchers develop ‘world’s first’ optical fibre with compound semiconductor core

According to Professor John Badding, who led the team, the zinc selenide compound could create a new class of optical fibre, offering significant advances in laser radar technology. "Such technology could be applied to the development of improved surgical and medical lasers, as well as better countermeasure lasers used by the military and superior environment sensing lasers such as those used to measure pollutants," he said. Badding claims the long, thin fibres, which are three times as thick as a human hair, can transmit over a terabyte of information per second. "Compared to traditional silica glass cores, a crystalline substance like zinc selenide is highly ordered," he said. "That order allows light to be transported over longer wavelengths, specifically those in the mid infrared. We've known for a long time that zinc selenide is a useful compound, capable of manipulating light in ways that silica can't. The trick was to get this compound into a fibre structure, something that had never been done before." Using a high pressure chemical deposition technique developed by graduate student Justin Sparks, Badding and his team deposited zinc selenide wave guiding cores inside of silica glass capillaries to form the fibres. "The high pressure deposition is unique in allowing formation of such long, thin, zinc selenide fibre cores in a very confined space," said Badding. The scientists found that the optical fibres made of zinc selenide could be useful in two ways. Firstly, they observed that the new fibres were more efficient at converting light from one colour to another and secondly, the fibres provided more versatility, not just in the visible spectrum but also in the infrared. "Existing optical fibre technology is inefficient at transmitting infrared light," said Badding. "However, the zinc selenide optical fibres we developed were able to transmit much longer wavelengths. Exploiting these wavelengths is exciting because it represents a step toward making fibres that can serve as infrared lasers." Badding also believes the breakthrough could open up new avenues of research to improve laser assisted surgical techniques, such as corrective eye surgery. The team's research has been published in the journal Advanced Materials. Photo caption: Fabrication and morphology of ZnSe optical fibre waveguides: a) Schematic of the HPCVD process, where a high pressure precursor mixture is configured to flow into a capillary (left). When the capillary is heated, well developed annular films are deposited. Unreacted precursors, carrier gas and reaction byproducts are carried out of the fibre (right). b) Diascopically illuminated optical micrograph from the side showing the transparent, uniform ZnSe fibre core. The deposited structures can have a uniform cross section for as long as 4cm when made in a 10cm long furnace. c) Cross sectional scanning electron microscopy (SEM) image showing an overview of the silica cladding and ZnSe core. d) A higher magnification SEM image of the nearly completely filled core. Scale bars: b) 50 µm, c) 50 µm, d) 5 µm