The double-slit experiment, first performed by [Thomas Young] in 1801 provided the first definitive proof of the dual wave-particle nature of photons. A similar experiment can be performed that shows diffraction at optical frequencies by changing the reflectivity of a film of indium-tin-oxide (ITO), as demonstrated in an April 2024 paper (preprint) by [Romain Tirole] et al. as published in Nature Physics. The reflectivity of a 40 nm thick film of ITO deposited on a glass surface is altered with 225 femtosecond pulses from a 230.2 THz (1300 nm) laser, creating temporal ‘slits’.
The diffraction in this case occurs in the temporal domain, creating frequencies in the frequency spectrum when a separate laser applies a brief probing pulse. The effect of this can be seen most clearly in an interferogram (see excerpt at the right). Perhaps the most interesting finding during the experiment was how quickly and easily the ITO layer’s reflectivity could be altered. With ITO being a very commonly used composition material that provides properties such as electrical conductivity and optical transparency which are incredibly useful for windows, displays and touch panels.
Although practical applications for temporal diffraction in the optical or other domains aren’t immediately obvious, much like [Young]’s original experiment the implications are likely to be felt (much) later.
Featured image: the conventional and temporal double-slit experiments, with experimental setup (G). (Credit: Tirole et al., Nature Physics, 2024)
I really appreciate reading about new fundamental research on hackaday. Cool fundamental research deserves more publicity.
However, fundamental research is hard to communicate. I don’t have time to read the paper at the moment, but I come from another scientific discipline and I have positively no clue what this is about. I guess I could figure it out by reading the paper, but that’s kind of my point: You don’t need to provide an explanation about the possible uses, but wild concepts such as temporal diffraction need to be explained at least on a surface level.
It’s baffling even if you read the paper.
Basically they shown a light on a mirror which they could turn transparent with another laser.
They turned the mirror transparent twice in quick succession (you can see in the inferogram 0 – 1 picoseconds separating the transparent periods). They call the periods when the mirror is transparent “slits in time”.
Apparently when you do this the light that comes out now has a frequency distribution which looks like the classic interferance pattern in the spectrogram.
You’d expect that the light coming out would be just like the light going in, but no a distribution of frequencies comes out.
They call that the result of “temporal diffraction”.