Supercontinuum generation is when intense laser light of one color travels within a material, similar to glass, and expands into a spectrum of colors. The effect lets scientists produce light at colors tailored to specific applications in sectors like bioimaging, optical communications, and essential investigations of materials.
Until now, there were two ways to create a supercontinuum. A unique optical fiber, around 10% of the width of a human hair, could be used to concentrate light to very high intensity over lengths of a few meters. Alternatively, even more, powerful light from an amplified laser could be tightly focused on ordinary glass.
However, there are advantages to these approaches associated with their size, complexity, and cost of using an extremely high-energy laser or with the precise and fragile alignment needed to force light into an optical fiber only two thousandths of a millimeter in diameter.
Now, scientists from Heriot-Watt University have discovered a new method for achieving the so-called supercontinuum generation. Using the process, scientists could generate a wide range of colors from a single laser.
Professor Derryck Reid from the Institute of Photonics and Quantum Sciences said, “We’ve shown that combining a simple laser with a special, nonlinear crystal can create a supercontinuum directly. We’ve removed the need for either a high-power laser or delicate light coupling into tiny optical fibers. There’s a fundamentally new mechanism at work here: our specially engineered gallium phosphide crystal creates a cascade effect.”
“We illuminate the crystal with light from an infrared laser, some of which is converted to visible green light. This, in turn, generates more green light at a slightly longer wavelength, becoming first yellow, then orange, and working all the way out to the red. The weaker edges of the light can generate green at longer and longer wavelengths. This has never been reported before.”
“This is promising. We think we can make the spectrum of the light wider and more intense by optimizing the properties of the crystal.”
However, scientists think further work is required to determine whether the effect is specific to the special gallium phosphide crystal they used and whether it can be further amplified.
- Supercontinuum generation in orientation-patterned gallium phosphide. DOI: 10.1364/OPTICA.385200