Gauging interest for a live auction of Laser lab being downsized

[Eidetic]

The S-P 125 is a monster of a laser that will unfortunately be very difficult to give away, much more to sell. I have three in the collection, two of which I had to take to get other lasers! Anyway, I'm looking for a set of the feet for one of them. A pair of the chromed rods that support the head. If you decide to part one of yours out, please let me know. I'd also be interested in the power supply for parts.

[Jem]

Dale Harder has a 5 foot long hene that does 100mw. Yes you read the right. It's the ultimate for holographs with multi multi foot coherence.

Really??? Multi foot coherence length from a HeNe. Cool

[Eidetic]

Only going to get "multi-foot" coherence out of a He-Ne is with an etalon. That means he claims to have a 5' He-Ne head that gives almost 200mW without the etalon, and that's hard to believe. My guess is that he has an S-P 125 with the etalon extension (much longer than 5') that has a strong tube in it, but that'll still be only around 60mW.

[Jem]

Yeah Bob, there was a hint of sarcasm in my post . But still, 60mW of HeNe with decent coherence length, that is cool

[mixedgas]

Dale has one with an IR bore in it. The IR bores were wider, and etched to have more surface area. It has exceptionally low loss Brewster windows .So yeah, I saw it do 175 multimode at seal off. But when you put the etalon and tem00 optics in it, its going to do 100 for a while, and then when you put the etalon in, you might get 55 TeM00. But my question has always been, unless you overfill it to get the good lifetime (and less power) what good is 175 at seal off. Almost immediately after seal off the gas settles in, starts making impurities from the bore materials and settles down to a final, stable, shipping power, much lower then the "on station" power.
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Whitelights, Argons and Kryptons do something similar to this as well. I get fantastic power when I pump a tube, and lase it on station. However it falls off rapidly when it does not have the huge volume of gas that is in the pump station and has to fall back to the internal gas return bores for makeup gas.
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The current record for a HENE is 325 mW, two rectangular bore tubes in a V shape. However using rectangular bores to get there means it has a elliptical, multimode, beam shape.
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HENEs power is limited by the fact that it needs wall collisions to depopulate the lower atomic states in the lasing process. Thus HENE power is proportional to tube surface area. If you go too big, you get only outer ring lasing and then it winks out. SO there is an upper bore diameter limit as well.

Lasing between two parallel plates cures this in a limited circumstance, but a flat elliptical sheet of laser light is not too useful.
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I can get huge coherence length out of sealed mirror HENEs or even 127s by using a simple cavity length locking circuit, something that artistic Holographers have almost always ignored.
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Steve's current record is greater then 10 meters with an Argon locked to an iodine cell. We actually had the stabilized lasers on one bench jumping across the room isle to another larger table where the beam was used for spectroscopy. There was not enough room in the cramped lab to actually set up the required measure array, but I knew it was damn good. I find it ironic that the factory locking circuit was only six op-amps and a photocell, the designer was brilliant.
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Steve

[Jem]

Fascinating Info Steve, thanks for posting. Please forgive my ignorance but is the cavity length locking circuit similar to a fringe locker?

[Eidetic]

That TEM00 power is about the same as a fresh and clean Spectra-Physics 125 with its etalon.

[Draco]

now What i would want is something neat looking that i could put on a table and have humans ask what the heck that is and is it emitting deadly radiation, since that is not piratical i would be interested in gas laser heads like some off HeNe or argon ion that not need to work but just look like something an insane dragon would have in his/her lair, i like all the odd parts, if this was an online auction where we would bid over say a day or three this might work given we have the time to look at the item and decide if it would meet or needs. and as always working is always better. gas lasers will always have a place in my collection even if they are the size of a truck. I have a green HeNe and so bady want to take it apart to see the tube but am too paranoid of breaking it in the process, so i keep it in a safe drawer with it's power supply, since the tube lights like any HeNe i am fascinated it puts out green, even only at 1 mw, that was the shit back then, we are so lucky now with the diode lasers that produce almost any color we want. allthough instill want a kyptonite bean to put super man in his place,, now i am not an evil dragon it's still hard convincing these "hereo" types" that i mean no harm

[mixedgas]

Fascinating Info Steve, thanks for posting. Please forgive my ignorance but is the cavity length locking circuit similar to a fringe locker?

Think of it as a fringe locker for INSIDE the laser.
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Either the rear mirror is on a piezo, or heaters are applied to the resonator rods.. Very easy to do. Smaller hene tubes have some built in non-linear effects that allow you to lock them using nothing more then a pair of photodiodes, a polarizer, and a 5 watt heater wrapped around the tube.
So you can lock to an external cavity or etalon, non-linear effects inside the laser, a Bragg Grating, or a Iodine cell...
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The actual hardware is not difficult to make.

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Fringe lockers try to adapt an unstable world to a reasonable stable laser. .

Steve

[Jem]

Thanks Steve. Sometimes I wish I was intelligent

I find it hard to believe that no-one commercialised that idea. Perhaps not now in the days of stabilised DPSS, but in the earlier days of holography when mainly gassers were being used. Having said that I suppose you just used a nice big juicy argon with an Etalon fitted?

Thanks for the info though, I love to learn stuff like this