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FrozenGate by Avery

Crazy and idiot idea : Replace co2 with HeNe to build a POWERFUL hene laser?

The only limiting factor for holography is stability, so why wouldn't those lasers be suitable? With an appropriate aperture size and maybe an etalon you can get the required beam, and as long as your setup is stable you can just crank up the exposure time to get the required illumination.

Even rather tiny HeNes have been used for this job. You don't need something like my trusty 5+ W TEM00 single mode Argon to produce a hologram. The only real benefit of a high power is that you severly reduce the long term stability requirement for your setup.
 





Why_you said:
The only limiting factor for holography is stability, so why wouldn't those lasers be suitable? With an appropriate aperture size and maybe an etalon you can get the required beam, and as long as your setup is stable you can just crank up the exposure time to get the required illumination.

Even rather tiny HeNes have been used for this job. You don't need something like my trusty 5+ W TEM00 single mode Argon to produce a hologram. The only real benefit of a high power is that you severly reduce the long term stability requirement for your setup.
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I'd say coherence is more limiting than stability. "Stability" problems can have many causes, but all can be addressed easier than inadequate coherence. That's why the visible beam laser was such an enabler of holography, previously done with much lower coherence length mercury arc lamps.
 
No, not the output power stability, i'm talking about the mechanical stability of the setup: Laser, optical bench, optics, plate, object. The whole setup can't move further than half a wavelength or the hologram is toast due to interference.

That's what makes taking large holograms with low power lasers so tricky: Everything has to be stable within like 100 nm for quite a while if you don't have the light output to expose the image faster.

Coherence length is easy with gas laser, as long as you use an Etalon you're in the 10+ m coherence range, and an Etalon can basically just be a glass plate at an angle.
 
I wasn't thinking about power stability at all. :D Of course you're right about stability being a big deal for holography with CW lasers, but your list should include stability of the air around the things you mentioned too.

Amazing to think, all those years I was making holograms with He-Ne lasers having a foot of coherence length and all I had to do was put a piece of glass in the beam to get 10+ meters! You want an etalon in a He-Ne and you'll have to live with a Spectra-Physics 125 with the extended cavity on your table. :oops:

SP-125A Extended Cavity.jpg
 
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Eidetical said:
I wasn't thinking about power stability at all. :D Amazing to think, all those years I was making holograms with He-Ne lasers having a foot of coherence length and all I had to do was put a piece of glass in the beam to get 10+ meters!

You want an etalon in a He-Ne and you'll have to live with a Spectra-Physics 125 with the extended cavity on your table. :oops:

View attachment 75598
Click to expand...
give cavity extender and etalon pls 🥺
 
To get back on topic, here's a pic of a He-Ne with a large bore. A great start for lasers, but not practical. Especially with a tube made for another kind of active medium altogether. This is a Spectra-Physics model 115 RF-excited He-Ne head with boots but no feet. :)

6.2SP-115 at CLEO.jpg
 
To be fair, i've only ever seen the "one glass slice" Etalon in person in one laser, and that thing is my heavily modified SP 2000/2020. One of those things that's theoretically possible, but requires a huge amount of effort to do. But i got the SP from a laser scientist who was really into holography and went all out with this thing (massively improved power, every optic has its own inert gas purge, etc) so i wouldn't be surprised if he spent months getting the Etalon right.

But back to the topic, wouldn't use a glass tube for this. I think the best starting material would be a RF CO2 slab, just because you can pump quite a lot of power into it without having too many cooling problems.
 
At 1150 and 3390 larger bores can make sense. I'm well aware of the large bores.

I have a sealed mirror beastie made for obscure particle sensing applications lasing on a mix of primary lines. Raman lines, and four wave mixing lines. Around a 3-4 mm bore, and for a tube in the 14" class, the circulating power is amazing,. The last time we looked at it on spectrometer I found 18 lines in the visible and near IR. However the required optics required the absolute best coatings in the world. Not something a beginner could afford.


However, merely breathing on it results in massive transersve mode hops, there is no stability in the wavelength spectrum, While the mode profiles are constantly changing,, the frequency stability Is horrible. Except as a novelty, it is useless outside particle counting

Stece
 
There are oddities out there, ring gyro lasers with 40 meter paths, 5.4 micron Henes, large bore IR henes, attempts at 4 meter long bores. Henes made of hollow glass waveguide fibers Etc. At the end of the day, if you want high power red, your on a narrow bore.

For the record, the large ring gyros have 20-30 cm of bore length, and lase at around 100uW of output.

Yes, large bores were the origin, mostly in the IR but small bores win at power conversion.


There were even high pressure large bores ran 6328 pulsed, while the peak power was high, the average power was abysmal. The pressure for those tubes was well in excess of 20x what a CW tube is filled at.


Yeah, I know, historical tubes, But at the end of the day small bores following a certain p/D ratio win in the red in ease of construction and efficacy.

Steve
 
LSRFAQ said:
There are oddities out there, ring gyro lasers with 40 meter paths, 5.4 micron Henes, large bore IR henes, attempts at 4 meter long bores. Henes made of hollow glass waveguide fibers Etc. At the end of the day, if you want high power red, your on a narrow bore.

For the record, the large ring gyros have 20-30 cm of bore length, and lase at around 100uW of output.

Yes, large bores were the origin, mostly in the IR but small bores win at power conversion.


There were even high pressure large bores ran 6328 pulsed, while the peak power was high, the average power was abysmal. The pressure for those tubes was well in excess of 20x what a CW tube is filled at.


Yeah, I know, historical tubes, But at the end of the day small bores following a certain p/D ratio win in the red in ease of construction and efficacy.

Steve
Click to expand...
I have this laser built by H-Nu Systems in 1966 that has a bore of about 10mm and alternating electrodes down the length of the 70" long tube that I was told was a He-Ne. Intracavity space at the rear has a prism stage that's adjustable from outside the closed head. You think this may be one of the lasers you mentioned above? I have nothing about it except the date and what Bob A. told me when I bought it from him (after 20 years of trying).

H-Nu tube A.jpg
H-Nu tube E.jpg

H-Nu Supply A.jpg

H-Nu Supply B.jpg

H-Nu Supply C.jpg
 
I quote:

"
Abstract:
The pulsed helium-neon gas laser has provided pulse power more than three orders of magnitude above the average power afforded by CW operation. Analyses of the power-limiting factors show that still greater increases may be expected. By increasing the size of the laser tube several times, by optimizing the gas ratio and pressure, by optimizing reflectivity and transmissivity of the reflecting mirrors, and by controlling the shape and application of the exciting voltage pulse, peak power outputs in the kilowatt range are theoretically possible. A power of 100 watts has been achieved in the laboratory at pulse rates up to 250 cps. Such a result brings the gas laser out of the low power category and into the intermediate power range. The results of range calculations show that 100 w pulse power will provide a radar range of approximately 10 km against a target having a diffuse reflectivity of 0.1, and a range of over 100 km with a cooperative target. Against a bright cloud background only the cooperative target can be used. The range will then be reduced to approximately 20 km. An automatic tracking radar system has been synthesized utilizing the pulsed gas laser as a transmitting component. A brief parametric analysis has been made and some of the advantages of the optical radar over its microwave counterpart have been outlined. "

L. L. Antes; J. Goldsmith; W. McMahan

Note whom the authors ended up with, One went to Spectra, the Other founded ALC/HGM
Not sure about Dr. / Mr. Antes..

from

"Pulsed Helium-Neon Gas Laser Applications"​

IEEE Transactions on Military Electronics, Volume 8 , Issue 1 , January 1964

ieeexplore.ieee.org

Pulsed Helium-Neon Gas Laser Applications

The pulsed helium-neon gas laser has provided pulse power more than three orders of magnitude above the average power afforded by CW operation. Analyses of the power-limiting factors show that still greater increases may be expected. By increasing the size of the laser tube several times, by...
ieeexplore.ieee.org

DOI: 10.1109/TME.1964.4323105

Read the refs.

----------------------------------------------------------------------------------------------
The references are a who's who of visible and IR laser manufacturing history.

Steve
 
Either that or it is one in the 2.2 uM region that uses Helium and another Inert Gas that I do not feel comfortable about talking about in an online forum. Then again it could be anything.

Pulsed Ion Laser Holography brings up some real classics from the 70s.
Pulsed Argon Laser Holography does as well.

Keep in mind some large bore pulsed ion lasers with low rep rates operate at pressures in the turbopump only range, and either have huge gas ballasts or exotic refill systems to keep things around 20 microns or less. Not having fill control tends to make me thing that is a higher pressure tube.

There are lots of pulsed near/mid IR gas systems with larger bores developed but never commercialized, save for one that is important but little known due to it's use.

Steve
 
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" A power of 100 watts has been achieved in the laboratory at pulse rates up to 250 cps." !!!:oops:.

The tube is intact and all the supply guts look clean .... maybe this is the one gas laser I have that's worth repumping?!? :D
 
PROBABLY worth trying. At least it is a common Thyratron for once.

We can check the mirror coating easily enough with one of my digital CCD spectrometers.

Go read the paper(s) and check the pulse width though, picoseconds through nanoseconds... Not too much fun if your eye can't see the pico pulses, nano however are quite visible.

I just bought some interesting design stuff from the Late Great Cambridge Lasers Labs auction.. Like, um, the hard seal Windowing technology and the jigs/ovens/frit that SP and Lexel developed.

Incidentally the 124/127 Hene family uses a 9:1 mix.

.
 
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One of the reasons you don't see easily made hard sealed HENE lasers, is that the coating reflectivity can change when you fire the frit.
So you don't coat for exactly 632.8 in some cases. Even IBS coatings can change center wavelength when firing.

I have a factory gas mix 127-20 running 604 orange and 632 red right now. A friend had time to play with my mirror set collection that I didn't. I gave a second set of optics to the same guy and he has 1 red, 1 orange, and the 594 running on a 127-30. Only took a year of him fiddling with the optics to get all three lines at once, starting with 12 pieces of test optic from a certain estate sale of probably one of the best laser optics designers in the world. Was for sale on Ebay as "Lazer Lenzes" and I found it by accident. I have red, yellow, green, and multiline test sets. I have sealed mirror green mirrors by the gazillions. They are a little off, but when fired, they will go to where they should be.

I appreciate his efforts immensely, I will let him share the details in his own time. 12 factorial is a lot of permutations to run.

12 factorial is 12 x 11 x 10 x 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1

The sets I have evidently are for bracketing the manufacturing procedure.

On the 127s he only achieved microwatt flashes of green, the green needs far more He (I think, almost sure) then the other lines.

Steve
 
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