Ultra-fast world captured with ultra-thin films

A film just 250 nanometers or 0.00025 mm thick has given scientists a glimpse into the ultra-fast world.

The film is made of transparent conductive oxides, a class of material commonly used for smartphone touchscreens and photovoltaic systems.

Nanophotonics experts at Heriot-Watt’s Institute of Photonics and Quantum Sciences have proven that these materials can capture and measure ultrafast events much better than current systems.

This could lead to breakthroughs in many scientific areas, including: cell biology and chemistry, where reactions take place, and must be recorded, in a millionth of a billionth of a second.

The findings are reported in nature communication†

dr. Marcello Ferrera, assistant professor of nanophotonics at Heriot-Watt University, led the work with colleagues from the University of Glasgow and Purdue University in the US.

“The ultra-thin films we used are zero-index materials. Light behaves very differently in these materials because the refractive index, which describes the interaction between light and matter, approaches zero. This is a very difficult condition to achieve in common materials.

“This opens up a world of possibilities, because when the index is so small, the material becomes very sensitive to ultra-fast light incentives.

“We have used this improved optical sensitivity in a frequency-resolved optical gating or FROG system, which is one of the most fundamental tools to measure the evolution of ultrafast optical events.

“The final result was a remarkable improvement in all key metrics, including bandwidth, speed and energy efficiency†

Ferrera points out that its new system relies on readily available, ready-to-use materials. This means that the technology can move quickly from the laboratory to commercial application.

He points to another advantage of the system.

“This new zero-index FROG reduces fundamental power requirements and also provides a broader set of optical information that can be used in machine learning to improve robustness and accuracy when characterizing ultra-fast events.”