. On-chip visible-to-infrared supercontinuum generation with more than 495 THz spectral bandwidth Credit: http://dx.doi.org/10.1364/OE.23.019596
Sending information with the help of light is an exciting prospect for future technologies. It requires ‘light chips’, made of a special glass (already known for their extremely low losses) which now have been equipped with ‘active’ functionalities, eg generating, strengthening, and modulating light. Their chip is capable of creating a very wide light spectrum that runs from blue to infrared, 470 to 2130 nm wavelengths. By doing so they have made a light chip with the largest frequency range ever.
The width and regularity of the light spectrum plays a central role in fiber optics info transfer. With a broader spectrum and a large number of light channels set next to each other (individual colours), you can process a larger amount of information faster.
(a) Supercontinuum spectrum generated in a 5.5 mm long Si3N4 waveguide with
h = 1.0 µm, w = 0.8 µm, and Ep = 590 pJ. The spectrum extends from 470 nm (at a -30 dB
level) to 2130 nm, which is more than 495 THz. The spectrum is measured using an OSA
(red) and a near-infrared spectrometer (blue). (b) Photograph of the spectrum after being
dispersed by a diffraction grating. http://dx.doi.org/10.1364/OE.23.019596
Creating such a spectrum with many individual lasers is technically very complex, expensive and less precise. University of Twente scientists have now successfully managed to create a light chip with the broadest light spectrum ever. Their chip achieves a bandwidth of 495 THz = more thanhalf more than previous record. According to Prof. Dr Klaus Boller this broad spectrum demonstrates potential of the technology. “However, the most important breakthrough is that we have managed to create it with the help of materials that have already proven themselves in practice. These materials have the lowest optic losses on a chip and are, therefore, already extremely relevant. What’s more, the fabrication matches the standard processes in the chip industry, making it suitable for mass production.”
METHOD: To generate the broad spectrum, they shone laser light into a structure that guides light, called a waveguide, made of a glass-like material, silicon nitride, embedded in regular glass (silicon oxide). The shape and construction of the waveguide ensures that the laser light generates new colours of light as it passes through – in this case going from 4 THz to a remarkable 495 THz. With a new fabrication technique, the researchers created a structure that is thick enough, 800 nm to withstand cracking.
Spectral broadening of the supercontinuum in a Si3N4 waveguide with w =
0.775 µm as a function of the incoupled Ep. Note that for visibility a progressive offset
of 20 dB was added http://dx.doi.org/10.1364/OE.23.019596
The spectrum created by the chip is not constant, but consists of about 12M peaks that lie at exactly the same distance from each other so the spectrum looks like a hair comb. Frequency combs, a fast-growing field of research, make it possible to not only increase the speed of optic communication techniques, but also to greatly improve the precision of atomic clocks, telescopes, and GPS equipment.
https://www.osapublishing.org/oe/abstract.cfm?uri=oe-23-15-19596
http://www.alphagalileo.org/ViewItem.aspx?ItemId=156302&CultureCode=en
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