Nanophotonics experts from Heriot-Watt's Institute of Photonics and Quantum Science have recently proven that a film can capture and measure ultrafast events much more effectively than the present systems.
As specified in a Phys.org report, a film, only 250 nanometers, or 0.00025 millimeters thick, has offered scientists a sneak-peek into the ultrafast world.
Heriot-Watt University: Ultrafast world captured with ultrathin films https://t.co/jFTulqR6Xs
— India Education Diary (@indiaedudiary) June 29, 2022
The film is made of TCOs or transparent conducting oxides, comprising a class of materials usually used for photovoltaic systems and smartphone touch screens.
This development could lead to breakthroughs in a lot of scientific fields which include cell biology and chemistry, where reactions take place, and need to be captured, in one-millionth of one billionth of a second.
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Typical Tauc plot for an amorphous thin-film transparent conducting oxide (TCO)
Ultrathin Films, Zero-Index Materials
Assistant professor of nanophotonics Dr. Marcello Ferrera from Heriot-Watt University led the work which is published in Nature Communications, alongside colleagues from the University of Glasgow and Purdue University in the United States.
The professor explained that the ultrathin films they used are zero-index materials. Here the light is behaving totally different in the said materials as their refractive index, which is how the interaction between light and matter is described, reaches zero. This is quite a difficult condition to achieve in common materials.
Ferrera also said that their work opens up a world of possibilities as to when the index is very tiny, the materials begin to be very vulnerable to ultrafast light stimuli.
He said they used the said enhanced optical vulnerability in a frequency-resolved optical gating or FROG system, which is one of the most essential tools in terms of measuring the evolution of ultra-fast optical events.
The FROG System
According to RP Photonics Encyclopedia, the FROG system is an approach for the "complete characterization of ultrashort pulses." For example, for measuring not just pulse parameters like the pulse duration or pulse energy, but the full-time dependent electric field as well, which includes the optical phase, or equivalently, the optical spectrum which includes the frequency-reliant spectral phase.
This method has been pioneered by the research group of Rick Trebino, at the Georgia Institute of Technology. A usual setup for a FROG measurement is akin to that of an intensity autocorrector, except that the photodetector is substituted with a spectrometer, usually a spectrograph, which needs to be calibrated for acquiring the right spectral shape.
Essentially, a FROG measurement involves recording some tens or even hundreds of spectra for various settings of the two pulses' arrival time differences.
Such data can be demonstrated in the form of a so-called FROG trace, which is a type of spectrogram and displays with a color scale the strength as a function of time delay, as well as optical frequency, or wavelength.
Final Result
In this new study, a similar India Education Diary report said, the final result was a tremendous enhancement in all the key metrics, which include bandwidth energy efficiency, and speed.
Ferrera pointed out that this new approach depends on " readily available, off-the-shelf materials." Meaning, that the technology can quickly transition from the laboratory to commercial application.
He also pointed out another benefit of the new approach. Specifically, he said, this new zero-index FROG cuts fundamental energy requirements and offers a broader set as well, of information that can be employed in machine learning to enhance robustness and accuracy when characterizing ultrafast occurrences.
Related information about the speed of light is shown on The Slow Mo Guys' YouTube video below:
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