| Author |
Message |
Harveyx
Guest
|
 Posted:
Thu May 12, 2005 8:35 am Post subject:
Re: Focused homemade nitrogen laser? |
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"Sam Goldwasser" <sam@saul.cis.upenn.edu> wrote in message
news:6wwtq5qld9.fsf@saul.cis.upenn.edu...
| Quote: | Uncle Al <UncleAl0@hate.spam.net> writes:
Mark Fergerson wrote:
Sam Goldwasser wrote:
Dirk Bruere at Neopax <dirk@neopax.com> writes:
Sam Goldwasser wrote:
Dirk Bruere at Neopax <dirk@neopax.com> writes:
rgregoryclark@yahoo.com wrote:
I've seen the designs for low-cost home-built nitrogen lasers. But
these were for unfocused beams.
Is there a low-cost method to focus the beam to a spot in the
range of
say a few hundred microns wide?
Quartz lens?
The problem isn't the lens material as much as the beam quality. It
will be hard to focus the typical home-built N2 laser's output to a
very small spot.
Depends on the length of the laser cavity I assume, since its single
pass.
More than that. It depends on the mode structure of the beam.
I was going to mention mirror quality and how they're positioned
vs. cavity proportions...
Superradiant nitrogen lasers have messy output, as such or one pass
with a rear mirror. The cavity is irrelevant. The output is not
coherent. You might as well try focusing a flashbulb to a few microns
image radius.
Well, it's not quite that bad. Most of the light is confined to the
area of the the long narrow discharge gap.
|
Uncle Al overstates his case a bit.
Why dont we try numbers instead of words..............
Forget 'mode structure' for most N2 lasers, there is essentially none, they
are single pass. But neither is it *quite* 'a flasbulb'.
To a pretty good approximation crude nitrogen laseers have a divergence
which is about d/L where d is the 'tube' (discharge, often transverse)
diameter & L the length.
If you focus it with focal length F your spot diameter is just F*d/L
So, if you want 0.1mm, d is maybe 5mm & L maybe 200mm you would need a 4mm
focal length, which is operating at F~0,8
You might get a UV transparent microscope objective (at a price) that gets
near that, but its pretty challenging to put it mildly.
With a longer, thinner laser, and relax it to 'a few' hundred um spot, and
you would get into just about achievable regimes.
With longer focal lengths, the F number falls, & aberrations are rapidly
less of an issue - its rather far from diffraction limited!
Lens UV transparency at 337nm is an issue, especially for a thick short
focus lens.
Harvey
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Harveyx
Guest
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| Posted:
Thu May 12, 2005 1:28 pm Post subject:
Re: Focused homemade nitrogen laser? |
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"Uncle Al" <UncleAl0@hate.spam.net> wrote in message
news:42825BEC.4DBA557E@hate.spam.net...
| Quote: | rgregoryclark@yahoo.com wrote:
I've seen the designs for low-cost home-built nitrogen lasers. But
these were for unfocused beams.
Is there a low-cost method to focus the beam to a spot in the range of
say a few hundred microns wide?
337 nm. Fused silica, alkali halide, or alkaline earth fluoride
lens. A meniscus lens is preferred to lessen aberrations.
|
For roughly collimated to focus, a plano-convex lens is near optimum for
n~1.5; thats why they are so commonly available.
Put it the right way round, students often dont! (The exact solution is
indeed a near plano/vex meniscus; but the plano vex is what gets used.)
(Meniscus is optimum for higher index material, such a Ge in the IR.)
Silica or CaF2 would be the usual, available choices, (LiF & MgF2 also.) The
chlorides & bromides are OK in the IR where scatter is much less critical,
pain in the UV, & often form colour centres under UV irradiation, dependent
on the source.
You need a *UV grade* silica.
Down to
| Quote: | microns is gonna take some work - superradiant lasers are not coherent
and you'll need a large diopter rating (thick lenses are problems on
several fronts). I doubt Fresnel or binary optics configurations can
pull it off, especially if you need imaging in addition to
concentration.
|
See rough sum in the other post.
Basically I agree, but it is just about 'do-able'
Harvey
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Baugh
Guest
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| Posted:
Fri May 13, 2005 12:35 am Post subject:
Re: Focused homemade nitrogen laser? |
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Sam Goldwasser wrote:
| Quote: | Baugh <baconbaugh@charter.net> writes:
Sam Goldwasser wrote:
Dirk Bruere at Neopax <dirk@neopax.com> writes:
rgregoryclark@yahoo.com wrote:
I've seen the designs for low-cost home-built nitrogen lasers. But
these were for unfocused beams.
Is there a low-cost method to focus the beam to a spot in the range of
say a few hundred microns wide?
Quartz lens?
The problem isn't the lens material as much as the beam quality. It
will be
hard to focus the typical home-built N2 laser's output to a very small spot.
Cannot you by placing the lens far enough away from the laser obtain a
better focus? The distance will correlate off-line output with lateral
displacement. A lens of sufficient quality and wide enough for the
spread beam will then redirect more accurately to the focus.
Think of it in terms of the focused image for the distance to the laser
will move closer to the focus from infinity as you move the lens farther
away. (Again assuming no spherical aberation in the lens.)
You're not imaging the output aperture of the laser, you're trying to focus
the beam from the laser. As such, how far away you are isn't very relevant.
However, if you're implying that a large f-number lens is better. Sure.
|
No I was thinking for a fixed focal length but farther from the source.
As long as the diameter of the lens catches the width of the spreading
beam. Seems to me you could acheive focus up to the order of the
wavelength this way... assuming you could build perfect lenses of a
given focal length to arbitrary diameter.
| Quote: |
I'm not sure I'd go so far as to say they aren't coherent asn other posts
have stated, but there is a most one bounc from a rear mirror (which isn't
essential) and the light makes at most two passes through the laser. This
doesn't set up a nice mode structure. As everyone's stated, it is messy.
|
Right you would get a random mix of coherent "packets", each the
amplification of a single spontaneously emitted photon.
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Phil Hobbs
Guest
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| Posted:
Fri May 13, 2005 12:35 am Post subject:
Re: Focused homemade nitrogen laser? |
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Harveyx wrote:
| Quote: |
See rough sum in the other post.
Basically I agree, but it is just about 'do-able'
Harvey
|
Of course, if this is the Scientific American laser, it's a monster,
producing millijoule pulses a nanosecond wide, which will cause nice air
plasmas near focus. Focusing tighter than the air breakdown limit will
be a challenge even with good lenses.
The plasma will move rapidly towards the lens, to the point of drilling
holes in it if it's too nearby (I used to have a 40x microscope lens
with a nice 1-mm hole drilled in the front element from this effect).
Cheers,
Phil Hobbs |
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Guest
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| Posted:
Fri May 13, 2005 2:16 pm Post subject:
Re: Focused homemade nitrogen laser? |
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Bret Cannon wrote:
| Quote: | The divergence of a nitrogen laser can be as low as 1 mrad if I
recall
correctly. LSI used to sell a "near diffraction limited" version of
their
sealed tube nitrogen laser (they may still). It use an unstable
resonator
with the output mirror covering only 1/4 of the output aperture and a
I'm
not sure if the rear mirror was flat or curved. I did some work
using such
a laser focused to about a 50 micron diameter for laser ablation.
Bret Cannon
|
The application I had in mind is indeed for micromachining.
This page discusses laser micromaching using UV lasers:
Small Excimers Opening Up New Industrial Applications.
http://www.resonetics.com/SMexcimer_default.htm
And here's a report discussing micromachining with femtosecond laser
pulses; but it gives examples showing that nanosecond pulses, the
length of the pulses for the home-made nitrogen laser, can also be
using for micromachinging:
Femtosecond Laser Micromachining: Current Status and Applications.
http://www.exitech.co.uk/pdffiles/Femtosecond%20Laser%20Micromachining%20Current%20Status%20and%20Applicat.pdf
Bob Clark |
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Guest
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| Posted:
Fri May 13, 2005 3:04 pm Post subject:
Re: Focused homemade nitrogen laser? |
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Harveyx wrote:
| Quote: | ...
Uncle Al overstates his case a bit.
Why dont we try numbers instead of words..............
Forget 'mode structure' for most N2 lasers, there is essentially
none, they
are single pass. But neither is it *quite* 'a flasbulb'.
To a pretty good approximation crude nitrogen lasers have a
divergence
which is about d/L where d is the 'tube' (discharge, often
transverse)
diameter & L the length.
If you focus it with focal length F your spot diameter is just F*d/L
So, if you want 0.1mm, d is maybe 5mm & L maybe 200mm you would need
a 4mm
focal length, which is operating at F~0,8
You might get a UV transparent microscope objective (at a price) that
gets
near that, but its pretty challenging to put it mildly.
With a longer, thinner laser, and relax it to 'a few' hundred um
spot, and
you would get into just about achievable regimes.
With longer focal lengths, the F number falls, & aberrations are
rapidly
less of an issue - its rather far from diffraction limited!
Lens UV transparency at 337nm is an issue, especially for a thick
short
focus lens.
Harvey
|
For these homemade nitrogen lasers the tube is just filled with air
and made of transparent plastic, so is quite cheap. Then you could have
a tube length say the full length of your basement, say 10 meters,
10,000mm.
Then for a diameter of 25mm, you would only need a focal length of
40mm to get a spot diameter of 0.1mm. How are 40mm focal length, 25mm
diameter UV lenses pricewise?
Bob Clark |
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Sam Goldwasser
Guest
|
| Posted:
Fri May 13, 2005 3:55 pm Post subject:
Re: Focused homemade nitrogen laser? |
|
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rgregoryclark@yahoo.com writes:
| Quote: | Harveyx wrote:
...
Uncle Al overstates his case a bit.
Why dont we try numbers instead of words..............
Forget 'mode structure' for most N2 lasers, there is essentially
none, they
are single pass. But neither is it *quite* 'a flasbulb'.
To a pretty good approximation crude nitrogen lasers have a
divergence
which is about d/L where d is the 'tube' (discharge, often
transverse)
diameter & L the length.
If you focus it with focal length F your spot diameter is just F*d/L
So, if you want 0.1mm, d is maybe 5mm & L maybe 200mm you would need
a 4mm
focal length, which is operating at F~0,8
You might get a UV transparent microscope objective (at a price) that
gets
near that, but its pretty challenging to put it mildly.
With a longer, thinner laser, and relax it to 'a few' hundred um
spot, and
you would get into just about achievable regimes.
With longer focal lengths, the F number falls, & aberrations are
rapidly
less of an issue - its rather far from diffraction limited!
Lens UV transparency at 337nm is an issue, especially for a thick
short
focus lens.
Harvey
For these homemade nitrogen lasers the tube is just filled with air
and made of transparent plastic, so is quite cheap. Then you could have
a tube length say the full length of your basement, say 10 meters,
10,000mm.
|
And you're going to excite this laser how? :)
| Quote: | Then for a diameter of 25mm, you would only need a focal length of
40mm to get a spot diameter of 0.1mm. How are 40mm focal length, 25mm
diameter UV lenses pricewise?
|
4 mm f/l lenses are quite common. That's not the problem.a
--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html
Note: These links are hopefully temporary until we can sort out the excessive
traffic on Repairfaq.org.
Important: Anything sent to the email address in the message header above is
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Harveyx
Guest
|
| Posted:
Fri May 13, 2005 4:35 pm Post subject:
Re: Focused homemade nitrogen laser? |
|
|
<rgregoryclark@yahoo.com> wrote in message
news:1115978664.500553.297350@z14g2000cwz.googlegroups.com...
| Quote: | Harveyx wrote:
...
Uncle Al overstates his case a bit.
Why dont we try numbers instead of words..............
Forget 'mode structure' for most N2 lasers, there is essentially
none, they
are single pass. But neither is it *quite* 'a flasbulb'.
To a pretty good approximation crude nitrogen lasers have a
divergence
which is about d/L where d is the 'tube' (discharge, often
transverse)
diameter & L the length.
If you focus it with focal length F your spot diameter is just F*d/L
So, if you want 0.1mm, d is maybe 5mm & L maybe 200mm you would need
a 4mm
focal length, which is operating at F~0,8
You might get a UV transparent microscope objective (at a price) that
gets
near that, but its pretty challenging to put it mildly.
With a longer, thinner laser, and relax it to 'a few' hundred um
spot, and
you would get into just about achievable regimes.
With longer focal lengths, the F number falls, & aberrations are
rapidly
less of an issue - its rather far from diffraction limited!
Lens UV transparency at 337nm is an issue, especially for a thick
short
focus lens.
Harvey
For these homemade nitrogen lasers the tube is just filled with air
and made of transparent plastic, so is quite cheap. Then you could have
a tube length say the full length of your basement, say 10 meters,
10,000mm.
|
They 'could'; but given the very rapid discharge needed, it will have to be
transverse excited, & either a rather complicated delay system & one spark
gap, or lots of spark gaps...........
Realistically, a metre is a pain, & anything more pretty impractical.
250-500mm is far more the norm.
Harvey
| Quote: | Then for a diameter of 25mm,
|
Do any N2 lasers have that big a gap? Maybe, but Ive not seen one.
you would only need a focal length of
| Quote: | 40mm to get a spot diameter of 0.1mm. How are 40mm focal length, 25mm
diameter UV lenses pricewise?
Bob Clark
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Sam Goldwasser
Guest
|
| Posted:
Fri May 13, 2005 4:35 pm Post subject:
Re: Focused homemade nitrogen laser? |
|
|
"Harveyx" <removeh.rutt@ecs.soton.ac.uk> writes:
| Quote: | rgregoryclark@yahoo.com> wrote in message
news:1115978664.500553.297350@z14g2000cwz.googlegroups.com...
Harveyx wrote:
...
Uncle Al overstates his case a bit.
Why dont we try numbers instead of words..............
Forget 'mode structure' for most N2 lasers, there is essentially
none, they
are single pass. But neither is it *quite* 'a flasbulb'.
To a pretty good approximation crude nitrogen lasers have a
divergence
which is about d/L where d is the 'tube' (discharge, often
transverse)
diameter & L the length.
If you focus it with focal length F your spot diameter is just F*d/L
So, if you want 0.1mm, d is maybe 5mm & L maybe 200mm you would need
a 4mm
focal length, which is operating at F~0,8
You might get a UV transparent microscope objective (at a price) that
gets
near that, but its pretty challenging to put it mildly.
With a longer, thinner laser, and relax it to 'a few' hundred um
spot, and
you would get into just about achievable regimes.
With longer focal lengths, the F number falls, & aberrations are
rapidly
less of an issue - its rather far from diffraction limited!
Lens UV transparency at 337nm is an issue, especially for a thick
short
focus lens.
Harvey
For these homemade nitrogen lasers the tube is just filled with air
and made of transparent plastic, so is quite cheap. Then you could have
a tube length say the full length of your basement, say 10 meters,
10,000mm.
They 'could'; but given the very rapid discharge needed, it will have to be
transverse excited, & either a rather complicated delay system & one spark
gap, or lots of spark gaps...........
Realistically, a metre is a pain, & anything more pretty impractical.
250-500mm is far more the norm.
Harvey
Then for a diameter of 25mm,
Do any N2 lasers have that big a gap? Maybe, but Ive not seen one.
|
I think what he means is that once the beam spreads to 25 mm.....
--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html
Note: These links are hopefully temporary until we can sort out the excessive
traffic on Repairfaq.org.
Important: Anything sent to the email address in the message header above is
ignored unless my full name is included in the subject line. Or, you can
contact me via the Feedback Form in the FAQs.
| Quote: |
you would only need a focal length of
40mm to get a spot diameter of 0.1mm. How are 40mm focal length, 25mm
diameter UV lenses pricewise?
Bob Clark
|
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Sam Goldwasser
Guest
|
| Posted:
Fri May 13, 2005 4:35 pm Post subject:
Re: Focused homemade nitrogen laser? |
|
|
rgregoryclark@yahoo.com writes:
| Quote: | Sam Goldwasser wrote:
...
For these homemade nitrogen lasers the tube is just filled with
air
and made of transparent plastic, so is quite cheap. Then you could
have
a tube length say the full length of your basement, say 10 meters,
10,000mm.
And you're going to excite this laser how? :)
Then for a diameter of 25mm, you would only need a focal length of
40mm to get a spot diameter of 0.1mm. How are 40mm focal length,
25mm
diameter UV lenses pricewise?
4 mm f/l lenses are quite common. That's not the problem.a
...
How does input energy scale with the size of laser tube?
|
I would expect it to be linear. However, it's not only the energy, but
the timing - getting the excitation pulse to be in sync with the light
pulse is not trivial over any distance.
--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html
Note: These links are hopefully temporary until we can sort out the excessive
traffic on Repairfaq.org.
Important: Anything sent to the email address in the message header above is
ignored unless my full name is included in the subject line. Or, you can
contact me via the Feedback Form in the FAQs. |
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| Back to top |
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Guest
|
| Posted:
Fri May 13, 2005 4:35 pm Post subject:
Re: Focused homemade nitrogen laser? |
|
|
Sam Goldwasser wrote:
| Quote: | ...
For these homemade nitrogen lasers the tube is just filled with
air
and made of transparent plastic, so is quite cheap. Then you could
have
a tube length say the full length of your basement, say 10 meters,
10,000mm.
And you're going to excite this laser how? :)
Then for a diameter of 25mm, you would only need a focal length of
40mm to get a spot diameter of 0.1mm. How are 40mm focal length,
25mm
diameter UV lenses pricewise?
4 mm f/l lenses are quite common. That's not the problem.a
...
|
How does input energy scale with the size of laser tube?
Bob Clark |
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Guest
|
| Posted:
Sat May 14, 2005 8:35 am Post subject:
Re: Focused homemade nitrogen laser? |
|
|
Sam Goldwasser wrote:
| Quote: | rgregoryclark@yahoo.com writes:
Sam Goldwasser wrote:
...
For these homemade nitrogen lasers the tube is just filled
with
air
and made of transparent plastic, so is quite cheap. Then you
could
have
a tube length say the full length of your basement, say 10
meters,
10,000mm.
And you're going to excite this laser how? :)
Then for a diameter of 25mm, you would only need a focal
length of
40mm to get a spot diameter of 0.1mm. How are 40mm focal
length,
25mm
diameter UV lenses pricewise?
4 mm f/l lenses are quite common. That's not the problem.a
...
How does input energy scale with the size of laser tube?
I would expect it to be linear. However, it's not only the energy,
but
the timing - getting the excitation pulse to be in sync with the
light
pulse is not trivial over any distance.
...
|
OK, the problems with just using air at standard pressure may be
insurmountable for my application.
However, this page suggests homebuilt nitrogen lasers can be used for
micromachining with the lasing gas at low pressure:
The Nitrogen Gas Laser.
"This laser produces intense, short, pulses of UV radiation at 337.1nm
and is useful for applications ranging from microcutting to pumping dye
lasers. This is one of the easiest gas lasers to build 'from scratch'
although the electrical discharge circuitry must be carefully
designed."
http://www.technology.niagarac.on.ca/people/mcsele/lasers/LasersN2.htm
The page suggests a vacuum pump to get the nitrogen down to 25 torr,
about 3% of standard pressure, is simple and low cost.
This company has prices for low cost UV lenses:
UV Optics - PCX.
http://www.hiteckint.com/product/optics/leans-pcxuv.htm
They give a price for a 6mm diameter, 9 mm focal length UV lens as
about $5.00. This is a Hong Kong company however.
Bob Clark |
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nightbat
Guest
|
| Posted:
Sat May 14, 2005 2:24 pm Post subject:
Re: Focused homemade nitrogen laser? |
|
|
nightbat wrote
rgregoryclark@yahoo.com wrote:
| Quote: |
Sam Goldwasser wrote:
rgregoryclark@yahoo.com writes:
Sam Goldwasser wrote:
...
For these homemade nitrogen lasers the tube is just filled
with
air
and made of transparent plastic, so is quite cheap. Then you
could
have
a tube length say the full length of your basement, say 10
meters,
10,000mm.
And you're going to excite this laser how? :)
Then for a diameter of 25mm, you would only need a focal
length of
40mm to get a spot diameter of 0.1mm. How are 40mm focal
length,
25mm
diameter UV lenses pricewise?
4 mm f/l lenses are quite common. That's not the problem.a
...
How does input energy scale with the size of laser tube?
I would expect it to be linear. However, it's not only the energy,
but
the timing - getting the excitation pulse to be in sync with the
light
pulse is not trivial over any distance.
...
OK, the problems with just using air at standard pressure may be
insurmountable for my application.
However, this page suggests homebuilt nitrogen lasers can be used for
micromachining with the lasing gas at low pressure:
The Nitrogen Gas Laser.
"This laser produces intense, short, pulses of UV radiation at 337.1nm
and is useful for applications ranging from microcutting to pumping dye
lasers. This is one of the easiest gas lasers to build 'from scratch'
although the electrical discharge circuitry must be carefully
designed."
http://www.technology.niagarac.on.ca/people/mcsele/lasers/LasersN2.htm
The page suggests a vacuum pump to get the nitrogen down to 25 torr,
about 3% of standard pressure, is simple and low cost.
This company has prices for low cost UV lenses:
UV Optics - PCX.
http://www.hiteckint.com/product/optics/leans-pcxuv.htm
They give a price for a 6mm diameter, 9 mm focal length UV lens as
about $5.00. This is a Hong Kong company however.
Bob Clark
|
nightbat
Thanks for the relative posted subject info Bob, reference
links, and all additional info from contributing posters. Could be
useful for possible low cost contruction of initial Star Race D.R.I.L.L.
the nightbat |
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Zak
Guest
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| Posted:
Tue May 17, 2005 12:35 am Post subject:
Re: Focused homemade nitrogen laser? |
|
|
rgregoryclark@yahoo.com wrote:
| Quote: | Then for a diameter of 25mm, you would only need a focal length of
40mm to get a spot diameter of 0.1mm. How are 40mm focal length, 25mm
diameter UV lenses pricewise?
|
What about using a reflector?
Thomas |
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jonsinger
Joined: 18 Dec 2005
Posts: 1
Location: Maryland
|
| Posted:
Sun Dec 18, 2005 12:58 am Post subject:
Nitrogen lasers, micromachining, etc. -- |
|
|
1) Micromachining, or at least ablating a metal surface, is clearly possible with a nitrogen laser. References:
http://fizika.hfd.hr/fizika_a/av97/a6p097.pdf
http://fizika.hfd.hr/fizika_a/av98/a7p205.pdf
(...Etc. -- I think they wrote up work with at least 4 metals, maybe more. The name "Cubeddu" is misspelled in the text of a6p097, btw.)
http://www.iop.org/EJ/abstract/0022-3727/23/6/017
[Sorry that last one is only a reference; IOP charges for actual articles. Note the peak power and the pulsewidth in this quotation from the Scroogle.org hit for this one: "A nitrogen laser (Rebhan et. al. 1980, Cubbedu and Curry 1973) (power up to 1.3 MW, pulsewidth 15 ns) was focused onto the target surface ..."]
2) People have been speaking of the nitrogen laser mostly as if it were only possible to run it in superfluorescent mode, with a maximum of one mirror. Let's think about this for a moment: most of the high-performance machines put out pulses at leaset 10 nsec long (see above), and even a SciAm machine puts out a pulse that is about 6 nsec long if you build it right.
This means that you can perfectly well build a nitrogen laser with a regular cavity if you want to, provided you keep the cavity length reasonably short. In fact, I've seen at least one article where they mentioned seeing about 20-25% higher output with an output coupler than they did with only a rear mirror. Needless to say, a laser that is 2 feet long and puts out a ~10 nsec pulse won't have a fully-developed mode structure (and it won't be even remotely close to TEM00), but it should give you a cleaner and tighter beam than you'd get without a cavity, and the beam should focus to a better spot.
3) Why does the header at the top left of the page say "ElectonicsHelp" instead of "ElectronicsHelp"?
Cheers --
jon
PS: If anyone here thinks that a nitrogen laser isn't "really" a laser, please remember that LASER stands for "Light Amplification by Stimulated Emission of Radiation". It does NOT stand for "Light Emission from Inside a Fabry-Perot Resonator", it does NOT stand for "Light Emission with a Clearly Defined Mode Structure", and it does NOT stand for "Perfectly Coherent Light Emission Device". Just because the process is coherent at the quantum level doesn't mean that the output of a real-world device has to be [or even can be] equally coherent at the macroscopic level. Coherence at the macroscopic level is a measure, not a "yes or no" issue. |
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