Science & Technology

Supercontinuum Generation: Special, Nonlinear Crystal Combined With Laser Yields Breakthrough

Supercontinuum era caught on digicam. Credit score: Heriot-Watt College

Researchers have generated a variety of colours from a single laser after discovering a brand new course of for reaching so-called “supercontinuum era”

Supercontinuum era is when intense laser gentle of 1 shade travels inside a cloth, like glass, and broadens right into a spectrum of colours. 

The impact lets scientists produce gentle at colours tailor-made to explicit purposes in sectors like bioimaging, optical communications and elementary research of supplies.

Till now, there have been two methods to create a supercontinuum. A particular optical fiber, round 10% of the width of a human hair, may very well be used to pay attention gentle to a really excessive depth, over lengths of some meters. 

Alternatively, much more highly effective gentle from an amplified laser—of the type invented by the 2019 Nobel Laureates Strickland and Mourou—may very well be tightly centered into abnormal glass. 

These conventional approaches include disadvantages, related both with the scale, complexity and value of utilizing a particularly high-energy laser, or with the exact and fragile alignment wanted to drive gentle into an optical fiber solely two-thousandths of a millimeter in diameter. 

Photonics specialists from Heriot-Watt have demonstrated a brand new technique that mixes the very best of each worlds: a colourful supercontinuum from a bulk materials utilizing solely moderate-energy lasers. The breakthrough has been reported within the main journal Optica. 

Professor Derryck Reid from the Institute of Photonics and Quantum Sciences mentioned, “We’ve proven that combining a easy laser with a particular, nonlinear crystal can create a supercontinuum immediately. 

“We’ve eliminated the necessity for both a high-power laser or delicate coupling of sunshine into tiny optical fibers.

“There’s a essentially new mechanism at work right here: our specifically engineered gallium phosphide crystal creates a cascade impact.

“We illuminate the crystal with gentle from an infrared laser, a few of which is transformed to seen inexperienced gentle. This in flip generates extra inexperienced gentle at a barely longer wavelength, changing into first yellow, then orange and dealing all the best way out to the purple. 

“The weaker edges of the sunshine can generate inexperienced at longer and longer wavelengths. This has by no means been reported earlier than.” 

Professor Reid and his workforce say additional work is required to find out whether or not the impact is particular to the particular gallium phosphide crystal they used and whether or not it may be additional amplified. 

Professor Reid mentioned: “That is actually promising. We expect we will make the spectrum of the sunshine wider and extra intense by optimizing the properties of the crystal. 

“Seen supercontinua are already extensively utilized in life sciences imaging and spectroscopy, however are restricted by the properties of particular optical fibers. Our new method may supply a handy and compact different to those present gentle sources.

Reference: “Supercontinuum era in orientation-patterned gallium phosphide” by Marius Rutkauskas, Anchit Srivastava and Derryck T. Reid, 13 February 2020, Optica.
DOI: 10.1364/OPTICA.385200

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