Laser Light Casts a Shadow In a Groundbreaking Experiment

Hello and welcome! My name is Anton and in this video, we will talk about an experiment that shows how a laser can cast a shadow
Links:
Quantum computers:
#laser #shadow #physics

0:00 New bizarre discovery: light shadows
0:38 Shadows in a nutshell
1:15 Why lasers
2:00 Evidence
2:30 Experiment and what was done
5:50 Other materials and what's next
6:20 Additional discoveries and what it means
7:20 Conclusions

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Credit:
 R. A. Abrahao, H. P. N. Morin, J. T. R. Pagé, A. Safari, R. W. Boyd, J. S. Lundeen

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[hugosimoes]

Anton, you might the greatest science communicator in the world. What a masterclass on communication and science. I'm in your patreon. Really big fan here from Rio, Brasil.

[volodymyrkleban]

TL;DW One laser changes physical properties of a ruby such that the light of another laser is partially absorbed

[rhtcmu]

Actually a simpler version of a light shadow in terms of just photons casting shadows is the classic two slit experiment where the wave property of light shows the classic pattern of light adding and cancelling. This involves no atoms and does work in a vacuum. That said, I can think of a lot of interesting follow experiments from these electron effects to further confirm what we think we know in the Standard Model and perhaps get more observable precision in what we think we know. That said, Anton, you did a great job! Thanks! Electron Mass as resistance to a force provided by the Higgs field affecting photon-electron interactions seems to be illustrated here as well with lots of interesting experiments to speak to the time taken to move the electrons to the needed energy levels to block photonic absorption with photonic absorption. Really cool.

[Adallace]

So the laser is making the ruby cast a shadow by making the ruby absorb different wavelengths than usual? I don't understand why we would say the laser is casting a shadow but I'm probably misunderstanding it.

[zrebbesh]

This is a fundamental principle that could allow photonic transistors. Meaning, we could actually doing computation with light instead of having to transform it back into electricity for switching. This is important because light has much higher bandwidth.

[markzuckerman-powdercoatin]

You can see a shadow from a CO2 laser on Fluorescent material if you illuminate it with a UV light while pointing the laser at the surface. The Infrared light from the CO2 laser Suppresses the Fluorescence and creates a shadow. It's used to find the CO2 beam and check its profile, since it's invisible normally.

[thesilentgod]

Considering the sheer number of places lasers are used, something like this can be a real changer for many fields

[AvidGamer_toer]

Thanks Anton. Ive read thru a lot of comments ( Sort of regretably ) and, well, It seems this one has created quite a bit of a controversy. The good news is that we still really don't know. I watcg every day and appreciate you providing sources and ways for me to get involved. Going to school for science this spring and will be taking astronomy for my bachelors. Your videos have inspired me to go for it, the mysteries are seemingly limitless and I am hoping that I am intelligent enough to one day become an astrophysicist.

[dexterisabo]

This is huge because of capacitance. Capacitance is the chokepoint in why motherboards can't run at higher speeds. When the frequencies get to high, the traces on the board start interacting with each other like they were capacitors. A motherboard of light and shadow wouldn't do that no matter what frequency the optical trace was flickering at.

[hamjudo]

[Edit: I have now read the paper. It does state that the excited ruby atoms are what actually casts the shadow. They emphasize the shadow effect because unlike most commonly used mechanisms for switching light with light, it is independent of the illumination angle and not strongly dependent on the wavelength of the light being switched.

So, they have characterized a nonlinear optical interaction that isn't particularly useful for switching laser beams, but does make interesting shadow effects.]

Original comment: The green laser pumps some electrons on ruby atoms to a state where those electrons can absorb blue light. The experimenters managed to tune the process so it could absorb up to 22% of the blue light.

As optically modulated optical switching processes go, 22% doesn't sound very impressive. Perhaps the authors were describing this as "casting a shadow" because it is a relatively weak effect. However, it seemed like the shadow terminology was clickbait.

If they can find some pairs of laser wavelength combinations that lead to fluorescence, then they can make a true 3d display.

I will read more of the paper and see if it sheds light on their motivation.

[DoctorBombastusLeisure]

I'm not sure why this is considered unusual or unexpected. Optical non-linear absorption has been known about and studied for decades. The excited volume of the ruby should be considered as being a non-transparent object, so it'd be odd if a shadow didn't formed.

Also, while the green laser (or any light source of close enough wavelength) is necessary to create the excited volume of ruby, those excited states have a lifetime and they exist after the exciting beam is switched off, meaning the shadow can be cast for some time without the green light. That lifetime is probably puny (likely nanoseconds) and constantly decaying, but it still exists and will cast a shadow for a short time, showing the ruby is casting the shadow and not the green laser.

Also, if you could excite the crystal by other means, such as electrically, you'd see the same result and is also an area of research that has been studied for decades.

[SebSN-yf]

Grandios! Thank you very much for this video Anton!

[Personnenenparle]

If its instantanuous, thats pretty much an optical logical transistor. The absolute best scenario would be to find a material that do that with a single laser wavelength that come from 2 directions or have different phases.. Could allow a light logic circuit to work with a single source light and produce the whole calculation at the speed of light istead of the speed of transition of a material

[Songfugel]

If it'd be more defined and at a smaller scale, this could be used make photon based transistors and computers

This might still be provide very interesting possibilities for analog quantum computers

[Thewsx]

amazing discovery, sounds like this would have big implications with optics

[stusacks]

Anton, you blow me away everyday with something interesting, fascinating or head scratching. I wish we can share a beer one afternoon. You seem to be a fascinating person and would love to know more about you. Anyway, never stop, your fans really appreciate what you do.

[diegofloor]

From a qFT/standard model perspective, light can interact with light. A photon can become a pair of electron positron, which can then interact with other photons. So it's not exactly surprising in the theoretical sense, but it is surprising that someone found a way to make it. I'm sure the interaction inside the crystal is orders of magnitude more complex than that though.

[Bassotronics]

I’ve talked about this a few years ago about a flashlight that casts black light pretty well (technically a shadow). My flashlight has a circuitry that analyzes the wavelengths that’s reflected off the wall then it shines a light that matches the exact same wave length but inverted and it casts a shadow on the wall. So it’s pretty much a flashlight of a darkness instead of a flashlight of visible light.

[davefoc]

I thought this might be an experiment where an extremely powerful laser beam might be able to block some light that otherwise would pass through it. I'm a little disappointed that this wasn't what this video was about, but I'm moving on with my life.

With regard to what the video was about, this result didn't surprise this non physicist. A material needs to have shell energy levels that won't absorb the energy of photons passing through it. If you zap the material so that it does have energy levels that allow it to block a beam, it seems like a nice technical accomplishment but it also sounds like it isn't completely unexpected that something like that is possible.

[primoroy]

Until it can be accomplished in a vacuum (without material to cause the effect), it is NOT a true "light shadow" but merely the result of manipulation of material properties (like electrochromic glass)!