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Detect ultrafast light with its strength

May the force be with you: detect ultrafast light with its force

Credit: McGill University

A McGill research team has developed a new technique to detect nano-sized imperfections in materials. They believe this discovery will lead to improvements in optical detectors used in a wide range of technologies, from cell phones to cameras and optical fibers, as well as solar cells.

The researchers, led by Professor Peter Grutter of McGill̵

7;s physics department, used atomic force microscopy to detect ultrafast forces that arise when light interacts with matter. In their article, published this week in PNAS, show that the forces resulting from two delayed light pulses can be detected with sub-femtosecond precision (they are millionths of a billionth of a second) and nanometric spatial resolution in a wide range of materials.

Improved technique for using light to detect imperfections in materials

“To understand and improve materials, scientists typically use light pulses faster than 100 femtoseconds to explore how quickly reactions occur and determine the slowest steps in the process,” explains Zeno Schumacher, the document’s first author who was postdoctoral in the Grutter laboratory when the research was conducted and is now based at ETH Zurich. “The electric field of a light pulse oscillates every few femtoseconds and will push and pull the atomic-sized charges and ions that make up matter. These charged bodies move or polarize under these forces and it is this movement that determines the material’s optical properties. “

The actual materials used in solar cells (also known as photovoltaics) and in optical detectors used in equipment such as cell phones and cameras have many imperfections and defects of different types which are very difficult to characterize, as they usually only have a nanometer in size. . Furthermore, it was very difficult to identify and study the “hot spots” and “weak links” in materials that can slow down or hinder the processes induced by light because traditional techniques for detecting the average of imperfections compared to the differences in properties in a larger area.

See nano-scale imperfections in a wide range of materials

The new technique developed by the McGill team combines ultrafast nonlinear optical methods with the high spatial resolution of atomic force microscopy. They demonstrated that their technique works on an insulating nonlinear optical material (LiNbO3) as well as a two-dimensional nanometric semiconductor jib of molybdenum diselenide (MoSe2), an inorganic compound used in optical microscopy and the scanning probe.

“Our new technique is applicable to any material, such as metals, semiconductors and insulators,” says Peter Grutter, senior author of the document. “It will allow us to use high spatial and temporal resolution to study, understand and ultimately control imperfections in photovoltaic materials. Ultimately, it should help us improve the solar cells and optical detectors used in a wide range of technologies.”

A nanoscale laser made of gold and zinc oxide

More information:
Zeno Schumacher et al., Detection of the nanoscale force of an ultrafast nonlinear optical response, Proceedings of the National Academy of Sciences (2020). DOI: 10.1073 / pnas.2003945117

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McGill University

May the force be with you: detect ultrafast light with its force (2020, 5 August)
recovered on August 6, 2020
from https://phys.org/news/2020-08-ultrafast.html

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