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Science Forum Index » Optics Forum » Most efficient laser?
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| Richard Saam |
 Posted: Mon Apr 28, 2008 8:34 am |
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Question:
What is the most efficient laser
as far as (power output) / (power input)
It could be expressed in many units
perhaps:
photons/watt
Richard D. Saam |
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| Phil Hobbs |
| Posted: Mon Apr 28, 2008 12:13 pm |
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Richard Saam wrote:
Quote: Question:
What is the most efficient laser
as far as (power output) / (power input)
It could be expressed in many units
perhaps:
photons/watt
Richard D. Saam
In photons per watt, a CO2 laser is almost certainly the champ. It's
about the most efficient gas laser around, watt for watt, and its
photons are about 20 times less energetic than visible ones, so you get
a boost of 20x right there.
In terms of (beam power)/(wall plug power), diode lasers win hands
down--slope efficiencies of over 25% are common.
Cheers,
Phil Hobbs |
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| Richard Saam |
| Posted: Mon Apr 28, 2008 4:06 pm |
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Phil Hobbs wrote:
Quote: Richard Saam wrote:
Question:
What is the most efficient laser
as far as (power output) / (power input)
It could be expressed in many units
perhaps:
photons/watt
Richard D. Saam
In photons per watt, a CO2 laser is almost certainly the champ. It's
about the most efficient gas laser around, watt for watt, and its
photons are about 20 times less energetic than visible ones, so you get
a boost of 20x right there.
In terms of (beam power)/(wall plug power), diode lasers win hands
down--slope efficiencies of over 25% are common.
Cheers,
Phil Hobbs
Thanks for the reply
In a possible related matter,
on page 639 of HECHT Optics
the concept of Self-Focusing of Light is addressed.
Quote:
"When a dielectric medium is subjected to an electric field
that varies in space (laser beam),
an internal force will result."
"This has the effect of altering
the medium permittivity (refractive index)
causing the medium to act as a positive lens
increasing the flux density over the incident laser beam.
UnQuote
The HECHT quote assumes a material medium.
QUESTION:
Is there a geometric arrangement
of intersecting (standing wave?) laser beams
(with defined cross section >> laser wave length^2)
which would create a dielectric medium (volume)
which would have the above self-focusing properties
within the medium (volume)
to the incident beams?
Intuitively, it would appear the more photons the better effect.
Richard D. Saam |
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| Sam Goldwasser |
| Posted: Mon Apr 28, 2008 6:33 pm |
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Phil Hobbs <pcdhSpamMeSenseless@pergamos.net> writes:
Quote: Richard Saam wrote:
Question:
What is the most efficient laser
as far as (power output) / (power input)
It could be expressed in many units
perhaps:
photons/watt
Richard D. Saam
In photons per watt, a CO2 laser is almost certainly the champ. It's
about the most efficient gas laser around, watt for watt, and its
photons are about 20 times less energetic than visible ones, so you
get a boost of 20x right there.
In terms of (beam power)/(wall plug power), diode lasers win hands
down--slope efficiencies of over 25% are common.
And with the DARPA initiative, they are probably approached/exceeding
80 percent slope efficiency by now.
In fact, even commercial high power laser diodes are well over 50 percent
in slope efficiency and even in wall plug efficiency at max power.
I like your idea of maximum photons/watt though. :)
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| Don Klipstein |
| Posted: Mon Apr 28, 2008 7:10 pm |
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In article <6LwRj.26361$Rr7.11710@newsfe29.ams2>, Skywise wrote:
Quote: Richard Saam <rdsaam@att.net> wrote in news:D%qRj.264749$cQ1.60053@bgtnsc04-
news.ops.worldnet.att.net:
Intuitively, it would appear the more photons the better effect.
Would not coherence be a factor? That is, just crossing any two
laser beams would not have an additive effect, even if they were
the same wavelength. I would think the electric fields would have
to be in phase.
If you add together two laser beams with random phase relationship
throughout their intersection area but otherwise identical, the "whole" on
average is indeed the "sum of the parts".
At the spots where the light from both sources is in-phase, electric
field is doubled and power density is quadrupled. At the spots with full
cancellation, electric field and power density are zero.
If you pass a laser beam through a beamsplitter and then have the two
beams converge onto a spot on some target at an angle to each other,
average brightness throughout the spot will be the same as if you never
split the beam to begin with (assuming the beamsplitter and other optics
are lossless). The spot will have a bandy interference pattern with the
centerlines of the bright bands being twice as bright as the average
intensity.
After the beamsplitter, each beam has half the original power density
and 70.7% of the original electric field. In the brightest spots of the
interference pattern where the beams recombine, the electric field is
141.4% of that in the original beam. (Assuming no optics losses.) Power
density is proportional to square of the optical frequency electric field
(and magnetic field also). Electric fields add linearly, once accounting
for phase.
So, the law of conservation of energy continues to hold true!
- Don Klipstein (don@misty.com) |
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| Skywise |
| Posted: Mon Apr 28, 2008 10:38 pm |
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Richard Saam <rdsaam@att.net> wrote in news:D%qRj.264749$cQ1.60053@bgtnsc04-
news.ops.worldnet.att.net:
Quote: Intuitively, it would appear the more photons the better effect.
Would not coherence be a factor? That is, just crossing any two
laser beams would not have an additive effect, even if they were
the same wavelength. I would think the electric fields would have
to be in phase.
And even so, this self lensing implies it occurs over the length
of the lights travel through the medium. Where two beams cross,
there's not a lot of medium, as opposed to, say, a single beam
traveling for several meters through something.
Just my amateur 2 cents.
Brian
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| Skywise |
| Posted: Tue Apr 29, 2008 9:48 pm |
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| Jürgen Appel |
| Posted: Thu May 01, 2008 12:21 pm |
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Skywise schrieb:
Quote: OK, perhaps I was thinking that self lensing is a non-linear
effect. If not, then I goofed.
Self-focussing is a nonlinear effect. It occurs when the refractive index of
a material depends on the light intensity. Under these conditions the Laser
beam can form a gradient index lens that leads to a change of the laser's
spatial mode dependent on its intensity.
With enough power this effect occurs in almost all media. Also the effects
are not necessarily as nice as one would imagine: Due to slight
inhomogenities in the laser's transversal mode profile or the material the
beam can split into multiple filaments.
Cheers,
Jürgen
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