Mirrors for SP 125

Does anyone know where to find a set of mirrors for an SP-125 for the yellow HeNe line? I've been told by several sources that they were an option for the SP-125 but so far I haven't been able to track down a set.

Thanks

Did you check in at SP to see if they are still even available?

They said they could make some for me........for a price.

Right... was that price more or less than a yellow HeNe tube?

I would like to know for my own sake!

I have the 125 extended manual. Not rated for yellow. Shortest line supported by the 125 with internal prism to prevent 633/3.39u /1.5 u competition is 611.8, it does that with the existing 633 optics and the prism. Power is not rated in the manual for that.

Yellow/Green likes a different gas fill. I have the data in research publication on yellow and green in 127s. 127 has done yellow, but I've never heard of a 125 doing it.

400-700 HR with radius would be about 250$ for a US made optic, but a OC-would be 750-1000$ from the same custom optics source. They would like a written statement from your lawyer that you will not sue them if it does not work. I've ordered similar things.

What you would probably have to do is measure the single pass gain as a amplifier using a external yellow hene and calculate the OC transmission from that.

Manual says #14-1 part number for the 633 only OC
#14-2 is 1.15 u
#14-3 OC is 3.39 u
#14-4 is the tunable OC with reduced power at 632.8,
but supports 611.8 and 640 nm

Maximum power at 611.8 is obtained with a #14-5 which supports weak lasing at 6328.8 and 640.1 nm

Manual says #14-1 will support lasing at 611.8 with reduced power on the 611.8 line.

Radius is 6 meters for the OCs, Broadband prism reflector for tunable operation is #26-1

from the drawings, it looks like 26-1 is a Littrow Prism (well, we know its a Littrow) with a broadband coating on a flat rear face.

Steve

"Right... was that price more or less than a yellow HeNe tube?"

more, by about a factor of 3

"Yellow/Green likes a different gas fill. I have the data in research publication on yellow and green in 127s. 127 has done yellow, but I've never heard of a 125 doing it."

Yeah, it's time to re-gas this sucker anyway, but I can do that part myself. I'm only getting ~57 mW out of it at the moment but at it's best I've gotten over 150mW out. I got this laser cheap and VERY used on feebay. The first thing I had to do was regas the tube and since it wasn't a hard seal tube I went ahead and spliced in a fill stock for future reference.

Are you really getting 57mw from a 150mw tube?

Would you please post some pictures of this device?

That's got to be a big one.

Never seen a pic' of an SP-125? They're about 2 meters long. My tube was a pull from an old peice of typesetting equipment of some kind. Mine differs from the standard SP-125 tube in that it has only two electroldes instead of the normal split arrangment with three. These were made custom for the manufacturer of the typesetter. They can be found pretty cheap from time to time on the surplus market but they generally need lots of work (including regassing and building a power supply) before you'll see them lase. I'll post a pic' or two when I can get to it.

Hey thanks, that would be much appreciated!

I've seen what the exterior looks like, but that's not what interests me so much. :evil:

The pics on the FAQ are kind of tiny.

So with a 2 meter long tube, how much 594.5 can be had after the gas mixture has been changed and the mirrors have been replaced?

Here are some decent pictures.

The trick is going to be how to suppress the 3.39 u competition. That is what the Prism is there for. I have plenty of lexel intracavity prisms, if you want to try one on the 125.

I'll find the publication on yellow/green and get back to you.


PS, big hene fans, take a look at this:

http://www.spectral.it/hene_laser.html

Spectrals usually do like 75 mW.

Yellow/Orange hene fans, take a look at this:

http://www.jainlasertech.com/laser.html



Steve

57 mW is not bad for a home regas. Do you have the RF add on to the exciter?

I've seen one do 210 on the pumping station at a lab near here.

---------------------------------------------------------------

I found the SP paper.

OK, the paper is in SPIE vol 737 New Developments in Gas Lasers, pages 76-79

Advances in Multiple Wavelength He-lasers
S. C. Sheng and D.C. Gerstenburger.

From reading the paper,

OC transmissions are unpublished, radius is unpublished.

Tube is a 2 mm bore , tube length is unstated.

Nice graphs though for fill pressure vs power for 543 only.

Green really needs a prism or magnet to kill 3.39 competition.

7:1 mix, 1.5 Torr, normal isotopic mix.
633 nm power = 40 mW
594 did 4.0 (notes say unoptimized optics)
543 did 2.5 mW

Looks like 543 likes a bit lower pressure then 633.

States gain for 543 is roughly 15 times less then the 633 line.

594 and 543 rise in power as tube current decreases.

Sounds like hene producers optimize bore diameter for the nonstandard wavelengths.

reading some of the graphs:
With pressure held constant:
633 peaked at 13 mA and lased from 10 ma to 13 mA
594 peaked at ~9.5 mA and lased from ~9.5 mA to ~11.2 mA
543 peaked at ~9.7 mA and shot downwards with a steep slope as current increased, but it did lase to almost 13 mA.

543 did its best performance when held to a constant 10 mA at 1.2 torr.


Since this is a 40 mW, 13 mA tube, my strong hunch is that it is a 127 frame.

Without knowing the optics transmission and radius, its tough to figure out what is going on.

They seem to go out of their way to hide useful data. I would not pay for the whole volume, just buy the paper itself for the graphs.

150/15 = 10 mW, maybe, for a 125 doing green.

Steve

LSRFAQ said:

PS, big hene fans, take a look at this:

CO2 lasers, He-Ne lasers & HVPS by Spectral

Spectrals usually do like 75 mW.

Steve

Click to expand...

Thanks for this. I have an RMM355L here doing 45mW. The multi-mode beam produces an intricate and beautifully patterned spot

Peace,
dave

Where did you get the gas to refill HeNes? I have most of the equipment and considered trying to refill some tubes for the challenge but I hit a wall finding a source of small quantities of the ultra pure gases for a reasonable price.

james1095 said:

Where did you get the gas to refill HeNes? I have most of the equipment and considered trying to refill some tubes for the challenge but I hit a wall finding a source of small quantities of the ultra pure gases for a reasonable price.

Click to expand...

I would not encourage buying expensive rare gasses in this economy. Expensive experiment.

At what UHP gasses cost, you might wish to go ordinary grade. My tank of UHP krypton was 700$ a few years ago. A "investor" bought it for me.

I only have argon, krypton, and helium. My UHP argon is medical surplus, and was cheap, at a auction with a surgical gas monitoring system.

For your purposes, ie a hobby project, welding grade helium is just fine.
Water vapor and residual O2 are well diluted when a tank is filled with 2500 PSI of 99.99% helium. Thus Helium comes from your local gas shop. Buy a tank of welding grade helium. You'll need lots of it to flush the vacuum system and to purge the tube. Do not try the BigBoxMART balloon stuff, unless you like water and air in your tubes. That was a ouch lesson.


Good quality Neon comes from EGL, inc in disposable tanks.

You can also buy neon in 2 litre glass flasks on Ebay or from neon supply shops. Beware, however, the flasks are lead glass, are only filled to atmospheric pressure or twice atmosphere. How you get from lead glass to a high vacuum system requires some creative thought as soft glass to pyrex adapters just do not exist any more. Usually its done with o-rings under compression. Ace Glass sells the compression assemblies.

1.25 Liter Flask Neon Gas Neon Signs EGL Brand | eBay

I think that is expensive, I have one here I paid 20$ & shipping for.

You have to seal a piece of soft iron in hard glass, this is inserted into the flask stem. You then use a magnet to strike the fragile seal inside the flask.
Once you do that, the flask is opened and must be used soon.

IF you read up on the neon bending web sites, I think you'll find what you need.

Cathode activation, I believe, is done with very pure O2 to a aux anode installed on the pumping station. I'm not 100% sure on that, I only do Ions. Its a rumor I've heard/read a few places. Any residual O2 or H20 kills lasing.

Hene, you might get away with a rougher and a dry ice cold trap. For Argon/krypton you NEED a turbo-pump and a Ti-Sub or Ion Pump. I need 10-8 to activate a ion laser's hot cathode.

See:
The Professor's Homebuilt Lasers Site - HeNe Lasers

Silver-Lead solders leak like crazy, Safey-silv56 is my weapon of choice, and even that is nasty for outgassing. He needed 1/8th inch or smaller copper, too.

Torr Seal would probably have bought him some serious operating time.



Steve