Parabolic mirrors concentrate sunlight to power lasers

Sep 12, 2011

Legend tells of Greek engineer and inventor Archimedes using parabolic mirrors to create "heat rays" to burn the ships attacking Syracuse. Though the underpinnings of that claim are speculative at best, a modern-day team of researchers at the Scientific and Production Association in Uzbekistan has proposed a more scientifically sound method of harnessing parabolic mirrors to drive solar-powered lasers.

Small scale analogs of giant reflector telescopes, these proposed ceramic lasers would convert an impressive 35 percent of the Sun's energy into a laser light, providing a considerable increase in the maximum power produced by current-day solar pumped lasers, which typically achieve only a 1-2 percent efficiency.

As outlined in the AIP's Journal of Renewable and Sustainable Energy, the new solar lasers would concentrate light with a small parabolic mirror 1 meter in diameter that has a focal spot approximately 2-3 centimeters in diameter. The concentrated light would then strike a two-layer ceramic disk known as a Neodymium and Chromium co-doped YAG (yttrium aluminum garnet) .

One side of the disk would have a highly ; the other side would be anti-reflecting. When sunlight penetrates through the , it excites the electrons in the material, causing them to emit laser light of a specific wavelength (1.06 micrometers). To control the searing heat produced by the concentrated sunlight, the ceramic disk would be mounted atop a heat sink through which water would be pumped.

The laser light would then travel to a prime focus and be reflected back to the ceramic surface before exiting the at an oblique angle. It's this "double pass" path that produces the gain in efficiency, enabling a greater fraction of sunlight to be converted into . Potentially, parabolic reflector lasers could be harnessed for the large-scale synthesis of nanoparticles and nanostructures.

Explore further: Finding faster-than-light particles by weighing them

More information: “Transformation of concentrated sunlight into laser radiation on small parabolic mirrors” by Shermakhamat Payziyev et al. is accepted for publication in the Journal of Renewable and Sustainable Energy.

Provided by American Institute of Physics

4.4 /5 (8 votes)

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SteveL
5 / 5 (2) Sep 12, 2011
Did the legend actually state "parabolic" mirrors? I certainly don't recall that, I only remember them described as "burning mirrors" and that in real conditions (multiple moving targets) the legendary result hasn't been duplicated.

Still, this is an interesting application - for daytime research anyhow.
axemaster
4.5 / 5 (4) Sep 12, 2011
in real conditions (multiple moving targets) the legendary result hasn't been duplicated.

I think "modern" people significantly underestimate the cleverness and fortitude of our forebears. After all, the siege of Syracuse lasted for several months, so a desperate genius with lots of helpers would have had plenty of time to get his mirrors/lenses working.
CSharpner
5 / 5 (5) Sep 12, 2011
MythBusters had a great episode on Archimedes' mirror weapon and got hundreds of college students to hold polished copper mirrors (to mimic what was most likely used at the time), each about 1 foot square, and focus them on a sale of a boat. The temperature barely moved up. Then they mounted the mirrors, focusing them on the sale, and got similar "non" results. I believe they then tried it with modern, more reflective mirrors while mounted, were able to get a little bit of scoring, but that's about it. And that was on a boat that was much closer than suspected in the real version and it was not moving.

The MythBusters concluded with a "Busted" conclusion.
SemiNerd
not rated yet Sep 12, 2011
The effect of a high intensity beam of light could blind the people on the ships, which would probably be just as effective as burning it up. You would not need an increase in temperature for the tactic to be militarily effective.
that_guy
not rated yet Sep 12, 2011
I'd agree with axe that our ancestors were more clever than we give them credit for - like building stonehenge or the pyramids. There is still a lot of controversy about 'how' they did it. So, although the mythbusters 'busted' this idea, I would still call it inconclusive, as we may not necessarily know exactly how they did it.

This will finally allow us to make war with lasers, using the power of the sun. Unfortunately, we won't be able to fight during bad weather or at night.joking of course ;)
CSharpner
5 / 5 (2) Sep 12, 2011
This will finally allow us to make war with lasers, using the power of the sun. Unfortunately, we won't be able to fight during bad weather or at night.joking of course ;)

Gives new meaning to the term "Eco-Warrior"!
John_balls
4.5 / 5 (6) Sep 12, 2011
MythBusters had a great episode on Archimedes' mirror weapon and got hundreds of college students to hold polished copper mirrors (to mimic what was most likely used at the time), each about 1 foot square, and focus them on a sale of a boat. The temperature barely moved up. Then they mounted the mirrors, focusing them on the sale, and got similar "non" results. I believe they then tried it with modern, more reflective mirrors while mounted, were able to get a little bit of scoring, but that's about it. And that was on a boat that was much closer than suspected in the real version and it was not moving.

The MythBusters concluded with a "Busted" conclusion.

For some reason I don't place the myth busters intellect and engineering prowess to be any where near the noted genius of Archimedes.
Nanobanano
not rated yet Sep 12, 2011
CSharpner:

Dan Rojas and his wife Denise were able to replicate it over a distance of a few scores of yards within a few minutes of trying.

It didn't even take anything fancy. He took regular flat mirrors and made some frames that allowed him to introduc a slight bend to the mirrors, etc.

Within a few minutes he had a mockup-up target fully engulfed in flames, with temperatures over 1070f...

The mythbusters just don't know enough about optics...nor did the MIT guys apparently.

http://www.youtub...CPX8r_9s

and

http://www.youtub...k1l0LjEs

A wall of such mirrors could have easily been used to catch fire to ancient wooden vessels, which were often pitched for water proofing.

The other thing is that burning human eyes woudl be a lot easier than burning wood. You could just as well blind the enemy army.

Admittedly, this test is at 100ft, so it would take a lot more mirrors to out-range say, archers with burning arrows...
CSharpner
5 / 5 (3) Sep 12, 2011
Cool videos. Thanks Nanobanano. I'm undecided one way or the other, but the MythBusters had a pitched ship and they had it on the water and at a more realistic distance. They didn't use parabolic mirrors though. They made the assumption Archimedes wouldn't have (rightly or wrongly). They did, however, have them set up in a parabolic like grid. The problems they ran into were they couldn't keep all mirrors focused on one spot on a bobbing and moving ship. Dan and Denise had on abject on still land and much closer.

There would certainly be an issue with blinding the occupants though. I think it could be effective even if it doesn't burn the ships.

I'd like to see a mixture of the 2 methods. Use Dan's mirrors with the MythBusters' setup against a real ship on real water at real distances.
antonima
5 / 5 (1) Sep 12, 2011

This will finally allow us to make war with lasers, using the power of the sun. Unfortunately, we won't be able to fight during bad weather or at night.joking of course ;)


Oh, what a shame.. lol. I guess it would be a lot more effective in the middle east, no?
Nanobanano
not rated yet Sep 12, 2011
What may have actually happened regarding archimedes death ray is the blinding thing after all.

This could have been more of a psychological or "defensive" terror weapon, rather than destroying ships as a primary purpose.

Figure it's the ancient world, you're in a wooden boat trying to attack the enemy, wh en all of a sudden a small fire breaks out, and then the first two guys that try to throw water on it get their eyes burned out, you'd probably be scared to death, even if the fire wasn't big enough to be a threat.

However, someone would need to demonstrate this as an effective terror weapon with a greater effective range than the flaming arrows fired from the early composite bows of the time period.

For simply firing an arrow with an oil soaked tip which is burning at maximum range, I believe a composite bow could make a shot of perhaps 100 yards, depending on the wind.

In theory, the death ray was limited only by the horizon and the focal length of the mirrors.
Deesky
4.2 / 5 (5) Sep 12, 2011
able to replicate it over a distance of a few scores of yards within a few minutes of trying. He took regular flat mirrors and made some frames that allowed him to introduc a slight bend to the mirrors

The point is that using modern mirrors to prove/disprove the old legend really proves nothing. The best mirrored surfaces they would have had back then would me many times duller than a modern mirror.

Even even if you had hundreds of these and even if they knew how to focus the beam, they would still need to keep all the mirrors aimed on the one spot (more or less) for a significant period of time to get any heating. You have the problem of constant ship movement as well as each person's ability to maintain aim on some agreed spot way off in the distance.

And to be effective, it would need to work at a long distance because once the fleet is close enough to shore, it's already too late. It's also harder to aim at multiple vessels closer in. And the sun better be shining!
Nanobanano
1 / 5 (1) Sep 13, 2011
The point is that using modern mirrors to prove/disprove the old legend really proves nothing. The best mirrored surfaces they would have had back then would me many times duller than a modern mirror


I disagree.

he showed in the video that you can make a highly reflective mirror from just a piece of metal.

you realize the lighthouse at Alexandria was constructed around this time frame? These people were not completely ignorant of how to focus light.

Saying the Sun better be shining is a no brainer, but that's no different than using flame arrows to try to catch the ships on fire, because if it's raining, that doesn't work either.
Nik_2213
not rated yet Sep 15, 2011
IMHO, 'Burning Mirror' implies a curve, hence a focus. Perhaps he weaponised it from a cubit's distance to a useful range ??
Uh, a dichroic mirror in space plus this light-pumped tech could give useful energy transfer-- Beam-riding solar sails ?? Asteroid nudging ??
{ FWIW, 'sail'... }
david_b_mcneill
5 / 5 (1) Sep 16, 2011
One of the things that fascinates me about nay-sayers regarding this historic event is that it was the attacking Romans, who were not in the habit of announcing nor recording their defeats, who are the ones, not the defeated Greeks of Syracuse, who wrote of Archimedes successful destruction of the Roman fleet. Look at how it was the triangular shaped teeth of the antikythera mechanism that gave the clue needed to solving the riddle of the odometer, a riddle even Leonardo da Vinci failed to puzzle out to a successful conclusion because he was looking at it from the wrong angle as did all those who came after him until we were handed an example of something from antiquity we thought either "inconceivable" or "impossible".

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