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Finally, a True Green Laser
dusty writes "Remember those green lasers from Star Wars? Turns out that faking green lasers has been easy for years, but making true green laser diodes has been the stuff of science fiction. Until recently, that is. Now researchers from Japan have created the world's first true green laser diode. Until now, only red and blue laser diodes were available, and now with the addition of green, new TVs and projectors that are more efficient can be produced. And if you were wondering how green lasers pointers are already produced, it is a hack that involved doubling the frequency of an infrared laser. The new true green laser diodes have much higher efficiency than the current 6%, leading many to expect big time laser display breakthroughs in the near future. Ars Technica has a well-written article on this breakthrough."
A laser diode is much more robust than a laser diode and the frequency-doubling package of nonlinear crystals.
No kidding!!! What do you say at this point?
I can't wait to get my new RGB Laser TV(TM)! Finally all those myths about how you'll go blind from staring at the TV will be reality!
This guy's the limit!
me to be the first to say: "laaayyser".
I'm sure Al Gore is thrilled with this news of green laser technology.
This brings us one step closer to producing a Power Ring!*
*GL Corps version, of course. Making a Power Ring like the original Green Lantern's is just a matter of using the right kind of ancient magic.
http://alternatives.rzero.com/
Blue > Green > Red
At this rate, the next generation games consoles will need a UV power light.
All we need now is some true frickin' sharks and we're in business.
Summation 2
Were the energy weapons in Star Wars actually called lasers? That sounds uncharacteristically unimaginative.
Sweet. Now we just need it to draw on your eyeball.
And not blind you.
" Down inside the computer are three lasers - a red one, a green one, and
a blue one. They are powerful enough to make a bright light but not powerful
enough to burn through the back of your eyeball and broil your brain, fry
your frontals, lase your lobes. As everyone learned in elementary school,
these three colors of light can be combined, with different intensities, to
produce any color that Hiro's eye is capable of seeing.
In this way, a narrow beam of any color can be shot out of the innards
of the computer, up through that fisheye lens, in any direction. Through the
use of electronic mirrors inside the computer, this beam is made to sweep
back and forth across the lenses of Hiro's goggles, in much the same way as
the electron beam in a television paints the inner surface of the eponymous
Tube. The resulting image hangs in space in front of Hiro's view of Reality."
-- perl -e'print pack"H*","6e656d6f406d38792e6f7267"'
Firstly, I really don't see how the solid state lasers using frequency doubling are "fake" lasers.
Even so, outside the realm of small laser pointers, there are such a thing as gas lasers and they can produce a true green emission.
The possible breakthrough is the production of more efficient semiconductor lasers that emit in the green range, not the production of the first "True Green Laser".
Yeah, this is Slashdot...Whatever
Title should read "True green laser diode". 'Green' laser output has been achievable for for more than three decades with Argon ion, Krypton ion, and Copper vapor lasers. This just makes it more 'convenient' to achieve green output.
Sig this!
So will the Television industry bring back laser television technology now that they got a true green laser?
I am sure the guys building this laser would be more than a little pissed that you consider their laser 'fake' because it uses frequency doubling....
love is just extroverted narcissism
The linked wikipedia article states:
Why? Whats so special about green laser pointers?
If you were slowing down light to make it green you'd need to start with ultra-violet light, not infrared.
The real physics is well documented on Wikipedia. I recommend reading their page on non-linear optics.
So when can I buy my working Light Saber?
Every fan of I'm Sorry, I Haven't a Clue knows all about it.
Next you'll be telling us that Japanese scientists have given Samantha a voice.
I piss off bigots.
The goggles do nothing!
Karnal
There, I said it. Now we can get on with useful comments.
Dislike the Electoral College? Lobby your state to join the National Popular Vote Interstate Compact.
Nothing is slowed down. Light always goes at the same speed. Guess its name.
What happens in a non-linear crystal is that two infrared photons combine to make one more energetic photon. If you can achieve 100% efficiency, then you start with a beam of power P in the infrared and end up with a beam of the same power in green, but only half the number of photons, each photon having double the energy, at the same speed.
The heating comes from inefficiency (transparency is never 100%) of the crystal, not from slowing down.
This is all, of course, well-documented in the page you have linked to, but not read. A more specific page might be
http://en.wikipedia.org/wiki/Second_harmonic_generation
This is wonderful news! I should have the backing of environmentalists behind my plan of attaching lasers to sharks!
....what do other people say?
Do daemons dream of electric sleep()?
The heating comes from inefficiency (transparency is never 100%) of the crystal, not from slowing down.
On the other hand 100% transparency would be completely useless as it wouldn't alter the wavelenght at all, right?
I am the lawn!
The author of that article actually mentioned that we have been able to make green lasers, but that they are not efficient enough to be used.
Actually, the author of that summary mentioned that we have been able to make green diode lasers, but they are not efficient enough to be used for applications that need high efficiency. (they're used all the time for applications that don't need high efficiency-- laser pointers, for example-- take a look at google).
The author of the summary failed to point out that green lasers using technologies other than semiconductor diode lasers have been avalable for decades.
Copper vapor lasers are quite efficient, actually, although argon ion lasers efficiencies are indeed pretty low. Doubled YAG lasers are very commonly used for green-- a diode-pumped doubled YAG can get a wallplug efficiency of around 20%, IIRC.
http://www.geoffreylandis.com
Oh, Edmund... can it be true? That I hold here, in my mortal hand, a nugget of purest Green?
I don't mind dating a girl that has been with everybody, as long as she had a good shower afterwards.
Freakin' sharks with lazers on their heads.
Nothing is slowed down. Light always goes at the same speed. Guess its name.
Fred? John? Amelia? Wait, how many guesses do I get?
(As an aside, the speed of light depends on the medium through which it's travelling).
Let me c.
Hang on a minute, the article says light travels at the same speed in a vacuum. Stupid intarwebs. I'll fix Wikipedia and you can do all the others, OK?
Confucius say, "Find worm in apple - bad. Find half a worm - worse."
Nothing is slowed down. Light always goes at the same speed. Guess its name.
True in a vacuum, not true in practically anything else.
Finally! A year of moderation! Ready for 2019?
And don't forget to mention more ecofriendly sharks.
Goodbye DLP and LCD TVs and projectors.
Laser TVs:
- Have higher contrast ratios (talk about true black)
- Produce a range of colors broader than HDTV
- Use less energy
Unfortunately, they're still expensive. The only one that's available that I know of is the Mitsubishi Laservue. It's $7000 over at Amazon (http://www.amazon.com/dp/B001IAAD3K).
Hopefully, this green laser will make Laser TVs more of an (afforable) reality.
I void warranties.
Let me c [wikipedia.org].
+1 groaaan
That is not fully correct. It is true that the speed of light, in a vacuum, is a constant. But, the speed of light through a transparent medium is something less than c. How much light gets slowed down by a medium is frequency-dependent, as described by snell's law, which is how lenses are able to bend light.
The fact that the speed of light through a medium is less than c also allows for some more exotic phenomena, such as Cherenkov radiation, created when a particle's velocity through a medium exceeds that medium's speed of light (but definitely remains less than c).
From the article it says, "At Sumitomo Electric, they have overcome this problem by developing a GaN crystal which inhibits the efficiency drop, resulting in room temperature pulse operation of a laser diode emitting in the pure-green region at 531nm." Having worked on development of GaN blue lasers, there are a lot of challenges to getting a reliable, continuous wave (CW) diode laser that operates at this wavelength. My guess is they hammered their green diode laser with very short high power pulses just to get it to lase. So it is probably not a very useful laser if it cannot operate in CW mode.
Nothing is slowed down. Light always goes at the same speed. Guess its name.
We're not talking about light in a vacuum you know. Did you really not know that the speed of light in a transparent medium varies inversely with its refractive index? So (for example) the speed of light in diamond is about c/2.4 (2.4 is the approximate refractive index of diamond).
In some specially constructed materials light can be slowed down to near walking pace or even temporarily halted.
Clearchannel has developed a new business income stream after it finally found the means to project its posters on the moon!
Well, thanks for your wisdom, BubbaDave. Are you volunteering to be killed?
Oh... You mean other people will be killed, and Bubbas like you will do the killing. In that case, you have a mental problem, don't you?
They say the same thing, but they say it after the Canadian physicist.
SIG: HUP
Could somebody elaborate a little bit more on this?
What is the issue with just using Indium to tune the band gap of GaN laser to the green and just having an InGaN laser?
If someone is passing you on the right, you are an asshole for driving in the wrong lane.
Green laser pointer day at the ballpark will be a huge success.
the no
Now I have to go out and buy a Green-Ray Player.
.
Thanks a lot you damn scientists!!
.
Tsukasa: All I really want, is to be left alone...
Layz0rz!!
Nothing is slowed down. Light always goes at the same speed. Guess its name.
When you've quite finished being sarcastic, you might want to remember what you learned about refraction at high school. The constant "c" is the speed of light in a vacuum.
"Wise men talk because they have something to say; fools, because they have to say something" - Plato
Green lasers? No! I've just bought a Blu-Ray player and now it's out of date because Green-Ray will be out next year! Grrrr.....
bullshit, light can go at various speeds depending on medium. even zero.
I think he meant that the light always goes at a single speed speed through the non-linear optical medium.
velocity = wavelength * frequency
When you double the wavelength, you halve the frequency, and the velocity stays constant.
If you used refraction to slow down the light by half (relative to the speed of light in air), which would in turn compress the wavelength by half, the frequency/color would stay constant, and as soon as your photons return to the air medium, their velocity would double, the wavelength would expand, and the light would still be infrared.
:(){
So, RBG = White, right? Any new application from that?
Currently hooked on AMP
... to that kryptonite laser every evil scientist has been dreaming about for years!!!
From the Slashdot summary: "And if you were wondering how green lasers pointers are already produced, it is a hack that involved doubling the frequency of an infrared laser. The new true green laser diodes..."
The intention is not to say they are fake lasers. The former green solid-state laser devices aren't just laser diodes; they are diodes plus another complicated structure. The new green laser devices are true diode lasers.
Corrections to the Ars article:
"Ever wonder why projector systems and televisions don't use laser illumination?"
More important error, and my guess about the correct information: "For instance, blue laser diodes use a gallium nitride system, and figuring out how to get indium nitride to mix through the gallium nitride evenly turned out to be quite difficult."
Full Text PDF of the Applied Physics Express scientific paper. (Free)
"Shoop da whoop?"
How can I believe you when you tell me what I don't want to hear?
I don't like the use of public fields, please use a getter method.
Some languages have properties, or methods without parentheses: C#, for example.
Show me GreenRay
attach them to some friggin' sharks and i'll take 10!
APK quotes people (including myself) without context and should not be trusted. Just thought you should know.
DPSS lasers are not "hacks"... nonlinear optics is an extremely important subject in many, many fields, from medicine to military to laser shows (which typically use nonlinear optics to create both 532nm (green) and 473nm (blue) outputs).
Nevertheless, "green" has been the critical issue in the delay of laser TVs. Just a few months ago, scientists had already made great leaps by creating lasers that lased at around 500nm. DPSS lasers have been demonstrated to be ineffective in the creation of laser scanning TVs (though it has been done at lower resolutions--hence, why scanners work).
-- casual /. reader and passionate laser hobbyist
It's a bug in the language.
Deleted
Well, some lights simply goes through, some light is absorbed, and some light is converted. The heating comes from the absorption. So yeah, calling it transparency is a stretch. Let's say "if 100% of the energy would exit the crystal, either at its original wavelength or at the new one, then no heating would occur".
You're right, of course.
My point is, rather, that the slowing of light due to the index of refraction does not absorb energy. It is not a dissipative process. No heating or change of frequency occurs. SHG is a completely different process.
Maybe they can combine all the lasers and makes pictures that can be projected, and maybe even move.
No seriously, projectable high def video thiat should be visible in the daytime. This will probably pave the way for a whole new type of billboard and billboard regulations, which will pop up on any flat surface, hell even on non flat surfaces (clouds, etc)
this might wind up being obnoxious
Laser headlights for cars = less glare into oncoming cars.
..........FULL STOP.
I realize that I'm probably nitpicking, but isn't the speed of light constant in any medium? If the medium is transparent (to the particular wavelength) the speed is is c.
Writing " It is true that the speed of light, in a vacuum, is a constant." makes is seem like the speed of light in any other medium is either speeding up or slowing down.
isn't the speed of light constant in any medium?
No.
If the medium is transparent (to the particular wavelength) the speed is is c.
Never really paid attention in physics, did you?
Nick
You make my head explode every time you talk to me. And when your commenting, its like a lobotomy. You think that I am dumb, wont you just explain to me? I need a dictionary or car analogy.
Was I wrong to read that as if it was written by Gilbert & Sullivan?
[UID-HeinzIntel]
Few weeks ago was disclosed who will be the actor that will play Green Lantern, and now was disclosed what will be the laser that will play its ring. Probably in a few weeks will be disclosed who will be the villain and filming will start at last.
This is pretty awesome for the "toy" laser market too! Green lasers have always been pricey - I wanted to get a laser from Wicked Lasers but you can easily spend a few hundred dollars or more if you are tempted by the high powered ones. Better efficiency means its easier to make higher power, and no doped crystals means less concerns with complex alignment and cooling (the crystals get very hot!). I'd love to have a cheap high powered green laser!
In fact, here's a diagram of a typical green laser module with all the lenses and crystals aligned.
http://www.walshcomptech.com/repairfaq/sam/l54-101.gif
It's complex, to say the least!
-Taylor
Worldwide Military budgets: $2100 billion. Worldwide Space Exploration budgets: $38 billion. Really, world? Really?
would be to make a Green Lantern ring that uses green lasers controlled by Willpower. :)
Remember, Slashdot does not have a -1 disagree moderation, and no, troll, flamebait, and overrated are not substitutes.
Lets go home.
Actually, I forgot that Slashcode eats any < signs you simply type unless you include it in an html-tag. It was supposed to be "If the medium is transparent (to the particular wavelength) the speed is <= c.". The = as vacuum can be seen as a medium.
As for the speed of light in a medium not being constant, can you clarify on that? Does the photons speed up or slow down inside the medium? If so, how? Is it because the overwhelming part of anything isn't there (i.e. a vacuum between the nuclei and electron cloud)? Does it mean that if it takes light 1 second to travel through x meters of a particular medium, then it won't take 2 seconds to travel through 2x meters of that same medium?
I wasn't implying that speed travels at the constant c (299,792,458 m/s) through any medium, just that if you have light traveling through a medium at c_medium, then that speed is constant for that particular medium.
That being said 'no' isn't even close to being a useful answer to the question I asked.
It doesn't display the entire picture at the same time. It displays one pixel of the image. A laser pointer worth, and scans through the area change color. Doing so fast enough give the impressive of an organic image.
Most of the image is simply stored in your eye, much like zipping a laser pointer around gets some rather sudden streaking impression. That same concept with a laser scanning the area while changing colors does just fine.
The only thing we've really been missing is real green light. Though there are plenty of nanoprojectors already using the green-light hack.
Slashdot people tend to know a lot about technology, you may want to Google things before assuming their impossibility.
It is no longer uncommon to be uncommon.
"It doesn't work that well yet but, .." that's ok because the Japs will just sit back and let Scientists in Europe and America ACTUALLY invent it, just as they did the red and the blue. Then they can package it up and sell it to everyone in Europe and America in HD tv's via hyper-corruption. Yes, I can be bitter sometimes, no offense Japan (mm.. yes offense) Sorry *++*'
I apologize if my understanding of light and it's properties go slightly beyond that in the Wikipedia article but for everyone slamming "UnHolier than ever "you might spend some time reading up on the subject (go beyond Wikipedia). Light always travels the same speed no matter what medium it is traveling through. It's rate of travel appears to slow, when in actuality it's path merely gets longer.
According to my handy photonic spectrum wall chart, there are green lasers already: Argon ion, Copper vapor, Nd:YAG, Xe, and HeNe, as well as, of course, tunable dye lasers. Just not laser diodes, until now.
...the future crusty old bastards are already drinking the Kool-Aid.
Light travels at the speed of light. You can't "slow it down". You're referring to frequency doubling, which has nothing to do with the speed of the light. (As frequency doubles, wavelength halves.)
This guy explained it much better than I can, so I'll just leave it at that.
Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
If you used refraction to slow down the light by half
Technically, refraction only refers to bending the light, not slowing it down. The change in angle is caused by the different value for the speed of light in the media (vs. the speed of light in air, usually), it's true. However, "refraction" refers to the angle change, not the speed change.
To put that differently, you could aim the beam exactly perpendicular to the surface of the different media, in which case no refraction would occur. For the purposes of your experiment, however, everything else you said would be correct since the speed would still be different in that media despite no refraction occurring.
Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
I'm no physicist, but hold on a second.
snell's law, which is how lenses are able to bend light
Agree.
How much light gets slowed down by a medium is frequency-dependent, as described by snell's law
Disagree.
Now, how much light gets slowed down does vary with frequency, IIRC. That's why a lens can't precisely focus both ends of the spectrum, and for this reason even high-quality optics can have problems with coloured halos due to the different wavelengths of light not converging on the same point. (Unless I'm getting lenses and mirrors confused.)
However, Snell's law is about refraction, and refraction would work even if all the frequencies were slowed consistently in the transparent media. Refraction is dependent on the angle of incidence with the transparent media and the relative speed of light within and without the media. Frequency dependency isn't really a factor.
Again, I'm not a physicist, so feel free to correct me if I'm wrong.
Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
I get your question. The answer is still "no", but the answer you were looking for is...
http://en.wikipedia.org/wiki/Chromatic_aberration
Glass, for example, will refract red light slightly differently than blue light, because the red/blue wavelengths will travel at slightly different speeds in the glass. In practical terms, this means that no lens, no matter how perfect, can precisely focus light of all wavelengths onto a single point of white light. It will always have a slight coloured halo because it cannot refract all wavelengths identically.
Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
In other words, the speed of light at a particular wavelength through a particular medium remains constant?
I suppose, yes.
Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
And by the same token, one would expect UV-ray discs to be able to store even more data.
But don't try getting a tan inside your CD-player. You won't fit.
The speed of a moving photon is always c. It is because of the interactions with the matter in a substance that the photons are 'stopped' periodically, thus causing the apparent overall speed to be less than that in a vacuum.
This is noted in the fourth paragraph of the article you linked on Cherenkov Radiation from wikipedia:
"It is important to note that the speed at which the photons travel is always the same. That is, the speed of light, commonly designated as c, does not change. The light appears to travel more slowly while traversing a medium due to the frequent interactions of the photons with matter. This is similar to a train that, while moving, travels at a constant velocity. If such a train were to travel on a set of tracks with many stops it would appear to be moving more slowly overall; i.e., have a lower average velocity, despite having a constant higher velocity while moving."
Now it becomes a semantic question of whether one is referring to the apparent speed of light through a medium (which is variable), or the speed of the individual photons. (which is constant, no matter the medium.)
You can slow light down, speed it up, and even stop it altogether!
AFAIK blue lasers currently use the "frequency doubling" method. Which means no RGB yet (at least not cheaply).
The speed of light differs in different media, but it still travels at the speed of light (in that media). Once it passes through the media and back into air, it will once again travel at the speed of light in air. The frequency doubling has nothing to do with the speed of the light.
Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
That's weird. I just downloaded another copy. No charge. I certainly don't have a subscription.
Another topic: White text on a black background is difficult to read. And another: How would Lyx be for documents with no formulas?
It's obvious from the snarky tone that he didn't.
I must be dense, but I'm not seeing how this is going to help in making TVs and projectors. The diode-pumped green lasers we already have are not that expensive (about $100, I think), so they would not add much to the cost. The real problem seems like it would be brightness: you need a really bright laser to scan over that large 54" area and still remain bright to the eye. But the green lasers we have are already plenty bright. I think it's easier to get a bright "fake" green laser diode than a bright red one.