# What's the most powerful diode laser?



## paulr (Dec 9, 2004)

*What\'s the most powerful diode laser?*

Someone on the 100mw green laser thread mentioned CNI had a 1 watt(!) handheld infrared laser. Anyone know if that's a laser diode, or some other system? 

What's the most powerful laser I can get (infrared is ok), that I can turn on and off at high speed? The application is ultra-long-haul optical communication, bwahahahaha.


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## Quazar (Dec 9, 2004)

*Re: What\'s the most powerful diode laser?*

I have seen diodes in excess of 45 W, or if water cooling is not a problem, 250W.


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## Spec (Dec 9, 2004)

*Re: What\'s the most powerful diode laser?*

Rule #3254: If its handheld, its a diode. 
Rule #3254.1 If it contains a glass tube that magically eats multi-kilowatts of energy or a HENE, its not a diode /ubbthreads/images/graemlins/wink.gif

Please classify "ultra-long-haul"

If your thinking of using a modulated laser to pulse binary across open air please concider the fact that the junk in the air itself can destroy signal integrity.

When dealing with optical modulation for communications the best bet is fiber optics and relatively low power high stability laser diodes.


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## Quazar (Dec 9, 2004)

*Re: What\'s the most powerful diode laser?*

I think the only communication he has in mind is _smoke signals_


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## paulr (Dec 9, 2004)

*Re: What\'s the most powerful diode laser?*

I don't think I want to deal with water cooling. I don't mind having to set up the laser on a tripod and do some aiming with a scope, but want to keep cost and hassle under control. 

Ultra-long-haul: well, this is over distances were fiber would be completely impractical, heh heh. Free-space optical (or microwave) is the only possibility. And I want to run at much higher data rates than are possible with smoke signals. /ubbthreads/images/graemlins/wink.gif


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## paulr (Dec 10, 2004)

*Re: What\'s the most powerful diode laser?*

No more thoughts?

OK, I will fess up about what I mean by ultra-long-haul:

http://www.k3pgp.org/viseme.htm

I'd like to be able to send data the same way. Now is that cool or what?


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## Spec (Dec 10, 2004)

*Re: What\'s the most powerful diode laser?*

Cool? Yes, very.

Practical? No, Hell no. /ubbthreads/images/graemlins/wink.gif

The scattering effect of the atmosphere alone would destroy any form of modulation you can come up with. However Ill put some thought into it and see what I can come up with. Off the top of my head I think the easiest way would be to use a low orbit satellite as a router/amplifier...

I read that site, and I have to say: "Ill believe it when I see it"


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## paulr (Dec 11, 2004)

*Re: What\'s the most powerful diode laser?*

Spec, ham radio operators have been doing moonbounce radio and even TV communications for many decades. I really would think optical wouldn't be that hard, but I'm no expert. I'd use direct sequence spread spectrum modulation, pulsing the laser at maybe 100 khz chip rate (3000 meters per chip) so that would be enough to average out atmospheric scattering within a few km of the receiver. On the transmit side I expect scattering effects to not amount to much.


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## photonics (Dec 11, 2004)

*Re: What\'s the most powerful diode laser?*

As I recall, the US did place a reflector at one of the landing sites. Perhaps, the first? Don't know what wavelength it reflects best 'tho.


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## QuestionDUDE (Dec 11, 2004)

*Re: What\'s the most powerful diode laser?*

the most powerful laser diode i know is 500mW . . .


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## WildRice (Dec 11, 2004)

*Re: What\'s the most powerful diode laser?*

IR diodes power output is way higher than visible. Also I just checked the link... are you using YAG at 1064nm, or harmonic. Pure YAG output diverges ALOT, even of you could compensate for atmospheric disturbances, you would never hit the moon.
Jeff


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## WildRice (Dec 11, 2004)

*Re: What\'s the most powerful diode laser?*

PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011

Contact: Diane Ainsworth

FOR IMMEDIATE RELEASE July 21, 1994

During their brief moon walk 25 years ago, the Apollo 
11 astronauts deployed a variety of scientific experiments, 
including a reflector array left in the fine powder of the 
Sea of Tranquility that continues to measure the moon's 
orbit around Earth to unprecedented accuracy.

Scientists who analyze data from the Lunar Laser 
Ranging Experiment have reported some watershed results from 
these long-term experiments, said Jet Propulsion Laboratory 
team investigator Dr. Jean ****ey. The team's findings 
appear in this week's issue of Science magazine, which 
commemorates the silver anniversary of the Apollo 11 lunar 
landing. 

"Using the Lunar Laser Ranging Experiment, we have been 
able to improve, by orders of magnitude, measurements of the 
moon's rotation," ****ey said. "We also have strong 
evidence that the moon has a liquid core, and laser ranging 
has allowed us to determine with great accuracy the rate at 
which the moon is gradually receding from the Earth."

The laser ranging retroreflector was positioned on the 
moon in 1969 by the Apollo 11 astronauts so that it would 
point toward Earth and be able to reflect pulses of laser 
light fired from the ground. By beaming laser pulses at the 
reflector, scientists have been able to determine the round-
trip travel time of a laser pulse and provide the distance 
between these two bodies at any given time down to an 
accuracy of about 3 centimeters (about 1 inch).

The laser reflector consists of 100 fused silica half-
cubes, called corner cubes, mounted in a 46-centimeter (18-
inch) square aluminum panel. Each corner cube is 3.8 
centimeters (1.5 inches) in diameter. Corner cubes reflect 
a beam of light directly back toward the point of origin 
and, thus, allow scientists to measure the Earth-moon 
separation and study the dynamics of the Earth, the moon and 
the Earth-moon system. 

Once the laser ranging experiments began to yield 
valuable results, more reflectors were left on the moon. A 
reflector identical to the Apollo 11 mission reflector was 
left by the Apollo 14 crew, and a larger reflector using 300 
corner cubes was placed on the moon by the Apollo 15 
astronauts. French-built reflectors were also left on the 
moon by the unmanned Russian Lunakhod 2 mission.

Several observatories have regularly ranged the moon 
with these reflectors: one is located at McDonald 
Observatory near Fort Davis, Texas; another is located atop 
the extinct Haleakala volcano on the island of Maui in 
Hawaii; another is located in southern France near Grasse. 

The Lick Observatory in northern California also has 
been used in the past for the lunar laser ranging 
experiments and ranging programs have been carried out in 
Australia, Russia and Germany. Despite the difficulty of 
detecting reflected laser light from the moon, ****ey said, 
more than 8,300 ranges have been measured over the last 25 
years.

"Lunar ranging involves sending a laser beam through an 
optical telescope," ****ey said. "The beam enters the 
telescope where the eye piece would be, and the transmitted 
beam is expanded to become the diameter of the main mirror, 
then bounced off the surface toward the reflector on the 
moon."

The reflectors are too small to be seen from Earth, so 
even when the beam is precisely aligned in the telescope, 
actually hitting a lunar retroreflector array is technically 
challenging. At the moon's surface the beam is roughly four 
miles wide. Scientists liken the task of aiming the beam to 
using a rifle to hit a moving dime two miles away.

Once the laser beam hits a reflector, scientists at the 
ranging observatories use extremely sensitive filtering and 
amplification equipment to detect the return signal, which 
is far too weak to be seen with the human eye. Even under 
good atmospheric viewing conditions, only one photon -- the 
fundamental particle of light -- will be received every few 
seconds. 

The range accuracy of these reflectors has been 
improved over the lifetime of the lunar laser ranging 
experiments, the team noted in Science. While the earliest 
ranges had accuracies of several meters (or several yards), 
continuing improvements in the lasers and the detection 
electronics have led to recent measurements that are 
accurate to about 3 centimeters (about 1 inch).

From the ranging experiments, scientists know that the 
average distance between the centers of the Earth and the 
moon is 385,000 kilometers (239,000 miles), showing that 
modern lunar ranges have relative accuracies of better than 
one part in 10 billion. 

"This level of accuracy represents one of the most 
precise distance measurements ever made," ****ey said. "The 
degree of accuracy is equivalent to determining the distance 
between Los Angeles and New York to one fiftieth of an 
inch." 

Laser ranging has also made possible a wealth of new 
information about the dynamics and structure of the moon. 
Among many new observations, scientists now believe that the 
moon may harbor a liquid core. The theory has been proposed 
from data on the moon's rate of rotation and very slight 
bobbing motions caused by gravitational forces from the sun 
and Earth. 

Other recent findings from the laser ranging 
experiments include: 

-- Verification of Einstein's theory of relativity, 
which states that all bodies fall with the same acceleration 
regardless of their mass. 

-- The length of an Earth day has distinct small-scale 
variations, changing by about one thousandth of a second 
over the course of a year. These changes are caused by the 
atmosphere, tides and the Earth's core.

-- Precise positions of the laser ranging observatories 
on Earth are slowly drifting as the crustal plates on Earth 
drift. The observatory on Maui is seen to be drifting away 
from the observatory in Texas.

-- Ocean tides on Earth have a direct influence on the 
moon's orbit. Measurements show that the moon is receding 
from Earth at a rate of about 3.8 centimeters (1.5 inches) 
per year. 

-- Lunar ranging has greatly improved scientists' 
knowledge of the moon's orbit, enough to permit accurate 
analyses of solar eclipses as far back as 1400 BC.

Continued improvements in range determinations and the 
need for monitoring the details of the Earth's rotation will 
keep the lunar reflector experiments in service for years to 
come, ****ey stated in her article.	

"For the immediate future, we have under way the 
implementation of dramatically increased station computing 
power, offset guiding capability and hands-off auto 
guiding," she reported. "The benefits from these 
improvements will not only be an increased number of normal 
points spread over significantly more of the lunar phase, 
but also a significantly increased number of photons within 
a given normal range.

"Farther down the road, we foresee the availability of 
more precise and more efficient photon detectors, such as 
micro-channel plates, significantly improved timing systems 
and shorter-pulse, more powerful lasers," she added. "This 
will increase data, provide higher accuracy ranging and 
improve sensitivity to lunar signatures, or conditions 
brought about by the phases of the moon."

At JPL the lunar ranging analysis is carried out by JPL 
scientists Drs. Jean ****ey, James G. Williams, X X Newhall 
and Charles F. Yoder. The work is sponsored jointly by the 
Astrophysics Division of NASA's Office of Space Science and 
the Solid Earth Science Branch of NASA's Mission to Planet 
Earth Office, Washington, D.C. 

Additional work is done at the Joint Institute for 
Laboratory Astrophysics at the University of Colorado at 
Boulder; at the University of Texas in Austin; and at 
Observatoire de la Cote d'Azur, Grasse, France.


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## Spec (Dec 11, 2004)

*Re: What\'s the most powerful diode laser?*

[ QUOTE ]
*paulr said:*
Spec, ham radio operators have been doing moonbounce radio and even TV communications for many decades. I really would think optical wouldn't be that hard, but I'm no expert. I'd use direct sequence spread spectrum modulation, pulsing the laser at maybe 100 khz chip rate (3000 meters per chip) so that would be enough to average out atmospheric scattering within a few km of the receiver. On the transmit side I expect scattering effects to not amount to much. 

[/ QUOTE ]

My "Believe it when I see it" post was based on the hardware he was using, not the actual process of doing it.

Photons are far less forgiving than electromagnetic waves and over that distance with that many variables I just dont see it as viable, however I would LOVE to be proven wrong here. /ubbthreads/images/graemlins/wink.gif


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## Shiftlock (Dec 12, 2004)

*Re: What\'s the most powerful diode laser?*

I agree with Spec here... Think about the divergence. Even with the lenses he claims, the "dot" cast on the moon would be miles wide. Then think about how much light would be reflected off of that little reflector, and how that would bloom before it hit the Earth. Also, think about the alignment challenge. Without doing a lot of calculatons that are way beyond me, I would have to say this is complete BS. Don't bellieve everything you read on the Internet.


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## cbfull (Dec 13, 2004)

*Re: What\'s the most powerful diode laser?*

[ QUOTE ]
*Spec said:*
Photons are far less forgiving than electromagnetic waves and over that distance with that many variables I just dont see it as viable, however I would LOVE to be proven wrong here. /ubbthreads/images/graemlins/wink.gif 

[/ QUOTE ]

Not to pick on you Spec, but I thought that light (i.e. a photon) is an electromagnetic wave. Maybe you mean radio or microwaves?

It seems like if we can receive continuous transmissions from sattelites in orbit, bouncing a beam of light off the moon should be simple. But then again, what do I know /ubbthreads/images/graemlins/tongue.gif?


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## comozo (Dec 13, 2004)

*Re: What\'s the most powerful diode laser?*

paulr said:
Spec, ham radio operators have been doing moonbounce radio and even TV communications for many decades. I really would think optical wouldn't be that hard, but I'm no expert.

Here's an analogy. Throw a stone at the side of a barn you'll see that it is very easy to do, now throw another stone an try to hit the flea on the side of the barn. You probably won't hit the flea the first time nor the second... Ham radio operators bounce radio off of the entire surface of the moon this is a shot gun approach.


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## comozo (Dec 13, 2004)

*Re: What\'s the most powerful diode laser?*

beam. How powerful does the light beam have to be? One laser generator in use with a 3.5-meter telescope operated by the Astrophysical Research Consortium at Apache Point, near Sunspot, New Mexico, generates a peak power of a one billion watts (1 gigawatt) for a short time, but just long enough to fire off a one-inch bullet of light aimed through the telescope at the lunar surface. 

The distance the light travels is calculated by measuring the light pulse's round-trip travel time and multiplying that figure by the speed of light. 

Earth's atmosphere distorts the beam so that it is expanded out to 1.25 miles in diameter when it hits the Moon. Only one in 30 million of the original photons in the beam actually will hit the retroreflector. By the time the light makes it back to Earth, the beam will have expanded to 9.3 miles in diameter. Of the returning photons, only one in 30 million will hit the telescope on Earth. 

http://www.spacetoday.org/SolSys/Moons/TheMoon/Retroreflectors.html


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## Spec (Dec 14, 2004)

*Re: What\'s the most powerful diode laser?*

[ QUOTE ]
*cbfull said:*

Not to pick on you Spec, but I thought that light (i.e. a photon) is an electromagnetic wave. Maybe you mean radio or microwaves?



[/ QUOTE ]

Photons act as a wave and a particle. Two completely different rulesets to use at the same time dealing with one "output"

AM radio frequencies cant make it under a bridge sometimes, while at the same time a metal mesh can stop it as long as the mesh itself is smaller than the "size" of the waveform. However a light/laser/whatever can make it through the mesh and bends through prisms and can create amazing shading because of its duality and ability to "bounce" off otherwise gain inhibiting substances.

Name me one radio(or higher if you are so inclined) frequency that is picky about the color it interacts with like a laser, heh. See? Neat to think about is it not?


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## paulr (Dec 14, 2004)

*Re: What\'s the most powerful diode laser?*

Comozo, thanks for those numbers. If 1/30e6 of the photons hit the reflector and 1/30e6 of those make it back, that means photons returning = (1/30e6)**2 = approx 1e-13 of the photons going out. Now they say they used a 1e9 watt laser, so that means about 1e-4 watts were coming back. That's actually quite a lot of light. A typical LED might have 3 volts Vf and be 10 percent efficient, so 1e-4 watts is like running a standard led at 0.3 mA, which is enough to light your way around a dark room, and is probably orders of magnitude higher than what you'd get from a GITD watch dial.


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