[HN Gopher] Lasers deflected using air
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Lasers deflected using air
Author : geox
Score : 161 points
Date : 2023-10-06 21:06 UTC (1 days ago)
(HTM) web link (www.desy.de)
(TXT) w3m dump (www.desy.de)
| gorpy7 wrote:
| cough lightsaber cough
| ge96 wrote:
| Lazy question, it's not possible for parallel lightwaves to
| interact and deflect orthogonally right.
|
| Point is to try and make a floating image.
| ricktdotorg wrote:
| can't wait for styropyro to try this!
|
| edit: for those who don't know -->
| https://www.youtube.com/@styropyro
| Terr_ wrote:
| I really like that this has a little interactive widget. Higher
| frequencies lead to more splitting/deflection, and higher
| pressure means more light traveling along the reflected path.
|
| That said, I must also admit that first video's still-image made
| me assume I was about to see the Master Control Program from
| Tron.
|
| > In their experiments, the researchers used an infrared laser
| pulse with a peak power of 20 gigawatts, which corresponds to the
| power of around two billion LED bulbs.
|
| OK, so not about to revolutionize photonic computers soon. :P
| lima wrote:
| The widget is also done very cleverly. It appears to be a
| regular HTML <video> element and a slider.
| novolunt wrote:
| [dead]
| HPsquared wrote:
| https://en.wikipedia.org/wiki/Gradient-index_optics
| anfractuosity wrote:
| Very interesting, would this be related to Acousto-optic
| modulators - https://en.wikipedia.org/wiki/Acousto-
| optic_modulator, which I believe can do this using a crystal and
| sound waves.
|
| Will have to read their paper.
| Jeff_Brown wrote:
| _Dang_ that 's cool.
|
| I'd like to know the turning radius.
|
| What do they mean by "efficiency" when they say, "In the first
| laboratory tests, a strong infrared laser pulse could be
| redirected in this way with an efficiency of 50 percent?"
| lilyball wrote:
| I'm assuming this means they deflected 50% of the laser light.
| Jeff_Brown wrote:
| Hmm, that seems problematic -- wouldn't that change it from a
| laser to a smear?
| promiseofbeans wrote:
| The article claims that it doesn't hurt the quality of the
| beam, it just reduces the amount of light
|
| > ... In contrast, we've managed to deflect laser beams in
| a quality-preserving way without contact.
| JohnFen wrote:
| Maybe? This is absolutely not my field, but I was watching
| a documentary on the largest visible light telescope that
| has ever been made and they were talking about the routine
| they follow when cleaning the primary mirror. The guy
| running the place said that when the mirror gets dirty, it
| doesn't degrade the quality of the image, but reduces its
| brightness (and so sensitivity).
|
| Maybe this is a similar kind of thing?
| bowsamic wrote:
| Oh nice! I work at DESY (don't know anything about this though)
| omneity wrote:
| The interactive component in the article was a really nice touch
| and made it much easier for me to understand the effect at play.
| I wish we could see more of this in technical articles and
| scientific publications.
| skulk wrote:
| (Off-topic tidbit that I noticed) The interactive widget is
| actually just a video with a fancy seek bar! If you right-click
| you can enable the controls and play it like a normal video.
| stavros wrote:
| Wow, that's a great idea.
| anontrot wrote:
| are we now a step closer to light saber? all we need is a 180
| degree deflection
| resist_futility wrote:
| It's always amazing how things thought of in science fiction end
| up becoming reality. In this case bending lasers in air, now we
| just need a small moon capable of retaining it's atmosphere.
| promiseofbeans wrote:
| That's no moon...
| Terr_ wrote:
| > a small moon capable of retaining it's atmosphere.
|
| That's easy, whatever it retains _is_ its atmosphere. :p
| dmbche wrote:
| https://en.m.wikipedia.org/wiki/Atmosphere_of_the_Moon
| Lucasoato wrote:
| How is this going to change the hypersonic missile industry? It
| seems that the only counter measure to hypersonic missile attacks
| would lie on destroy them with lasers (the only vector that can
| reliably and accurately go much faster than hypersonic missiles).
| If someone develops a technology to shield missiles with air,
| what else could take down such weapons?
| samus wrote:
| I guess it's the same difficulty as with reflective coatings -
| their efficiencies are far from 100%. Even if they manage to
| repulse most of the energy, some of it still goes through and
| roasts the missile. Also, this technology only seems to
| influence a laser beam passing by, not one about to hit head-
| on.
| semi-extrinsic wrote:
| The downside of hypersonic missiles is that they are travelling
| so fast, hitting a stationary object in the air will do
| significant damage - even raindrops can do damage. So if you
| detect the incoming hypersonic missile and just fill the sky in
| front of it with metallic particles, you're good. CSIS calls it
| "twenty-first century flak".
| beambot wrote:
| I'm highly skeptical that this hasn't already been done,
| considering that acousto-optic lenses are a known thing -- it's
| just a question of which material you're using (air, crystal,
| liquid, etc): https://en.wikipedia.org/wiki/Acousto-
| optic_modulator
|
| Even a 10-second Google search yielded examples of prior art. For
| example:
|
| https://iopscience.iop.org/article/10.1088/2515-7647/abc23c/...
|
| How is this any different? -\\_(tsu)_/-
| OldGuyInTheClub wrote:
| I wondered the same thing. Acousto-optic modulators and
| deflectors have been commercial items since the late
| 1970s/early 1980s. I used them in that era. They were even
| intrinsic parts of laser systems, sitting within the cavity to
| create pulses of various kinds.
|
| There's also a 50 year history of measuring dynamics in gas and
| condensed phase systems by the transient grating method which
| uses laser pulses to generate temporary gratings in all sorts
| of media. Two short (nanoseconds and on down) cross in a sample
| (solid, liquid, gas, flame, etc.). They generate an
| interference pattern and the fringe separation depends on the
| crossing angle. At points of high intensity, some kind of
| excitation is created and the refractive index gets modulated
| by the fringe pattern forming a grating. Now bring in a third
| pulse at a later time and it will scatter off of this grating.
| The grating will decay with time as the excitation relaxes due
| to whatever physical or chemical process is under study. Change
| the delay between the excitation and probe pulses to get a
| decay curve which is the observable to be fitted, modeled,
| compared with theory, etc.
| [deleted]
| _Microft wrote:
| It might not be clear from the reporting but I guess the
| paper's title (linked from the bottom of the article) might
| give a clue already:
|
| _,,Acousto-optic modulation of gigawatt-scale laser pulses in
| ambient air"_ ,
| https://www.nature.com/articles/s41566-023-01304-y (open
| access)
|
| Here's an excerpt from the abstract:
|
| _,,Modern photonics [...] can involve parameter regimes where
| the wavelength or high optical powers involved restrict control
| due to absorption, light-induced damage or optical nonlinearity
| in solid media. Here we propose to circumvent these constraints
| using gaseous media tailored by high-intensity ultrasound
| waves. We demonstrate an implementation of this approach by
| efficiently deflecting ultrashort laser pulses using ultrasound
| waves in ambient air, without the use of transmissive solid
| media. At optical peak powers of 20 GW, exceeding previous
| limits of solid-based acousto-optic modulation by about three
| orders of magnitude, we reach a deflection efficiency greater
| than 50% while preserving excellent beam quality."_
| fsh wrote:
| It's different because they are using a gas as an acousto-optic
| medium. This allowed them to work with laser intensities that
| are more than three orders of magnitude above the damage
| threshold of conventional solid-state acousto-optic modulators.
|
| Achieving good diffraction efficiency (they report ~50%) with a
| gaseous medium is a serious engineering challenge since the
| refractive index variations due to sound waves are many orders
| of magnitude weaker than in solids.
|
| I would suggest reading the original publication [1] for more
| details. It's open access.
|
| [1] https://www.nature.com/articles/s41566-023-01304-y
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