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”.
That is a much clearer explanation than the original item (sorry, Maya) (and pun unintentional). I do generally agree with [f__] that the article ought to summarise the paper and not expect the lay reader to puzzle out the details — otherwise why publish it here?
I still do not fully understand the significance of the interferogram, (the top and bottom scales are confusing), but as fundamental research it is intriguing.
its hitting a fairly common optical treatment with lasers from multiple angles, and its showing that as the reflectivity changes, its actually changing the light speed/frequency during the transition..
they say in the article there’s no clear uses atm.. but with the ability to alter the frequency of the light passing thru a lens by hitting it a separate laser source has.. interesting acedemic applications.
if you can slow down light a little you can slow it down a lot..
the only real world application i can think of has pretty far reaching implications
you can have variable frequency light sources instead of filtering a nearby frequency.
this seem to be to light as a VDO is to radio..
So, a really fast chopper, which is exactly what I need. If you could do this with a double slit and chop the slits in alternation so that they are never both open, you might get a result that is very interesting.
The best thing about Hackaday is the comments, this is a good comment that wouldn’t have existed without the article. Therefore the article is good.
someone should do the double pulse of light with the peppers ghost experimental setup to see what it looks like. it’s effectively the same as the article, but much lower tech.
And the power required is only 124 gigawatts per square centimeter: several million times hotter than the surface of the sun.
Yeah, sure, only for 0.2 picoseconds, but that’s an enormous power density: Sufficient to strip electrons from atoms, literally altering the very material it hits.
There’s some weird non-linear stuff going on here. Despite the confident explanation in the paper, I doubt it’s as simple as an interference phenomenon.
This experiment confirms the expectation that a temporal slit will also lead to diffraction and interference with itself – neat! .
Spatial diffraction is common around edges, so you build lenses to better shape the light. I would expect that if you turn a pulse of light just on and off, you will get ringing along the time axis.
I can imagine that you thus can do temporal beam forming (shaping the pulse?) in the long run, but that requires even higher modulation speeds.
Not sure where this matters… Yet
Fundamentally, all the authors have demonstrated is a different technique to modulate an optical carrier, right? There are a variety of commercial optical frequency and phase modulators that perform such a function already (see Thor Labs, Jen-optik and others). And there, you need not provide super-fast, high-power pulses. These components can be driven by a relatively low power microwave source pre-modulated by your favorite profile (not just on-off pulsing). So I feel like this demonstration lacks any novel flair but maybe there is something important about the ITO that I don’t appreciate.
Novel research aside, I do appreciate academic spirit of this article. The space/time equivalence of diffraction and modulation through the two-slit experiment is a fun way to think about those Fourier relationships.
I love this. The DSE and its implications have always fascinated me, and I have spent decades dreaming up different variations of the conditions to try to puzzle out the cause of the phenomenon. My ideas focused mainly on material and geometry of the slit, I never thought to throw the time domain into it!