A new type of optical fiber

A team of scientists from Penn State University in the USA has developed the first ever optical fiber consisting of a zinc selenide core - a yellowish compound used as a semiconductor 

A team of scientists from Penn State University in the US has developed the first ever optical fiber consisting of a zinc selenide core - a yellowish compound used as a semiconductor. The new family of these innovative fibers allows for more efficient and advanced control of light, which promises to pave the way for the development of a more versatile laser-radar technology. This technology could be applied to the development of improved surgical and medical lasers, better lasers of the type used as a means of protection in the military, and environmental sensing lasers of the type used to measure pollutants and detect the spread of chemical warfare agents by terrorists.

"It has almost become a cliché to say that optical fibers are the cornerstone of the current information age," said the lead researcher. "These tiny and long fibers, which are three times smaller than a human hair, are capable of transferring a terabyte (trillion bytes) - the amount equivalent to 250 DVDs. – of information in one second. And yet, there are always methods to improve existing technology." The researcher explains that the technology of optical fibers has always been limited to the use of a glass core. "Glass has a random atomic arrangement," notes the researcher. "In contrast, a crystalline material, such as zinc selenide, is remarkably ordered. This order allows light to pass through higher wavelengths, especially those in the mid-infrared."

Unlike silicate glass, which is traditionally used in optical fibers, zinc selenide is a semi-conducting compound. "We have known for a long time that zinc selenide is a useful compound capable of manipulating light in ways that silica cannot," said the lead researcher. "The trick was to create this compound in a fibrous structure, something that had never been done before." Thanks to an innovative high-pressure chemical bonding method developed in the laboratory of the researcher Badding, the researchers were able to insert Galbo cores (waveguide, the entry on Wikipedia) of a zinc selenide layer into the inside of silicate glass tubes to receive the new family of fibers the optics. "The high-pressure stacking is unique in that it enables the creation of long and tiny zinc selenide fiber cores with a highly defined structure," explains the researcher.

The researchers discovered that optical fibers composed of zinc selenide could be useful in two ways. First, they noticed that the new fibers were more efficient at changing light from one color to another. "When ordinary optical fibers are used for signs, displays and art, the desired colors are not always obtained," notes the lead researcher. "Zinc selenide, which utilizes a process known as nonlinear frequency conversion, is more effective in changing colors." Second, as the researchers had expected, they found that the new family of fibers exhibited greater versatility not only in the visible spectrum, but also in the infrared range - electromagnetic radiation with longer wavelengths than those of the visible range. Existing optical fibers are ineffective in transmitting infrared light.

However, the new optical fibers were also able to transmit the long wavelengths of infrared light. "The ability to utilize these wavelengths excites us because the finding represents a step forward towards the preparation of fibers that can be used as infrared lasers," explains the researcher. "For example, the army currently uses radar-laser technology capable of utilizing the wavelengths of the near-infrared range, or the range of 2.5-2 microns. A device that can utilize the mid-infrared range, or the range above 5 microns, will be more accurate. The fibers we developed are capable of transmitting wavelengths up to 15 microns."

The researcher explains that the detection of pollutants and environmental toxins could be another application of better radar-laser technology capable of responding with light of longer wavelengths. "Different molecules absorb light of different wavelengths; For example, water absorbs, or blocks, light with wavelengths of 2.6 microns," adds the researcher. "However, the molecules of pollutants or other toxic substances may absorb light with much longer wavelengths. If we are able to transmit light across longer wavelengths in the atmosphere, we will be able to locate the materials in it more clearly."

In addition, the lead researcher notes, zinc selenide optical fibers could pave the way for research that would enable the improvement of laser-based surgical methods, such as eye repair surgery.

The research findings were published in the scientific journal Advanced Materials.

The news about the study