EEVblog 1412 - Argon Ion Laser TEARDOWN

[EEVblog]

Dave tears down the 10W Coherent 300C Argon Ion laser. All 42kg, 1.2m and 24kW worth!

[alxpo]

The cylindrical side appendage could be a gas reservoir to replenish the argon lost through entrapment in the walls of the discharge tube by sputtering (not a photodiode).

[djacobow]

80C196KB! Nice to see it in a product. '196 was the first chip series I ever worked on. First job out of college at Intel in Chandler, AZ.

[EEVblog]

The cylindrical side appendage could be a gas reservoir to replenish the argon lost through entrapment in the walls of the discharge tube by sputtering (not a photodiode).

Yes, someone in the youtube comments said the same thing. Seems plausible.
The power output sensor is on the front as I showed. Shot that bit afterwards, forgot to correct.

[EEVblog]

80C196KB! Nice to see it in a product. '196 was the first chip series I ever worked on. First job out of college at Intel in Chandler, AZ.

Quite common in industrial stuff.

[CJay]

80C196KB! Nice to see it in a product. '196 was the first chip series I ever worked on. First job out of college at Intel in Chandler, AZ.

Quite common in industrial stuff.

Also in Automotive, I *think* the Ford EEC ECUs used a variant of it.

[Kareem]

The "lens" you held at 25:35 may not be the output mirror. Hear me out.

What you described in the video is a basic Fabry-Perot resonance cavity. These things are insanely sensitive to the distance between the mirrors, which leads me to believe that the 1% transmissive mirror is fixed within the black casing.

Now, I have three hypotheses as to what the thing you were holding is:
1- Wavelength filter (basically a band-pass filter for optical signals).
2- Waveplate (a piece of glass that have different refractive indices along its x-axis and y-axis). These, with a combination of other optical components, are sometimes used as optical isolators that prevent unwanted back reflections.
3- The actual acousto-optic modulator, which means that the two perpendicular barrels are piezo-electric transducers.

Of course I could be wrong in all fronts, but I think if hypothesis 3 is correct, you could do a few fun optical experiments.

Love the channel, been a long term viewer.

[Kleinstein]

The 99.x% refelctive mirror may not look like a mirror as it only should mainly reflect the blue light. Other light should come out of the cavity or at least attenuated more. The mirror is more like an interference filter made from multiple layer on the glass. So it is wavelength filter and mirror in 1 piece.  In some sense like Fabry-Perrot resonator, but only very short ( 1 wavelength ).

For a fixed wavelegth there is no need for a fancy acousto-optic modulator.

The facy looking metal bellow is likely just for dust protection and also to catch the beam in case something goes wrong. Just plastics may melt from the laser power.

[Kareem]

For a fixed wavelegth there is no need for a fancy acousto-optic modulator.

I thought I heard Dave mention that this model has an acousto-optic modulator. I could be mistaken.

The mirror is more like an interference filter made from multiple layer on the glass. So it is wavelength filter and mirror in 1 piece.  In some sense like Fabry-Perrot resonator, but only very short ( 1 wavelength ).

Like a Bragg-Grating? I think you're right. Fabry-Perot lasers typically have poor spectral purity as far as I know.

[Kleinstein]

A Bragg-Grating seems to be right name for the refelctor. The wavelength selective mirror is only for the corase range, Ar lasers have multiple wavelengths (AFAIR yellow and green besides the main blue line). There are still mutiple longitudinal modes, but for just illumination this is OK. It would be somerthing different for things like Raman scattering and the like. This may want extra measures.

[djacobow]

80C196KB! Nice to see it in a product. '196 was the first chip series I ever worked on. First job out of college at Intel in Chandler, AZ.

Quite common in industrial stuff.

Also in Automotive, I *think* the Ford EEC ECUs used a variant of it.

Good to know. At the time, this would have been early 90's, I seem to remember our main market was Western Digital hard drives.

[james_s]

The cylindrical side appendage could be a gas reservoir to replenish the argon lost through entrapment in the walls of the discharge tube by sputtering (not a photodiode).

IIRC that's exactly what it is.

Sam Goldwasser would know for sure, I don't think he's on this forum but his laser FAQ is easy to find. I'm pretty sure we have at least one member here with experience rebuilding ion lasers. Those were the holy grail of laser enthusiasts for many years, prior to high power diode lasers appearing about 10 years ago, 1W+ of visible laser light meant in most cases a large frame ion laser.

I still have a small aircooled argon ion laser that I fire up now and then.

[Kleinstein]

replenishing the argon and helium gas is usually not that important. The more problematic part with the gas is keeping contraminations low. So the extra part is likely more like a getter to catch any oxigen or water that for some reason diffused out of some walls or holes. The tube should be seal good enough to avoid loosing much of the wanted gas, but it only take a relatively small amount of the wrong gases to cause problems.

[james_s]

In case anyone has not seen it, this was for many years the definitive source of hobbyist information on ion lasers.

https://www.repairfaq.org/sam/laserarg.htm#argtsw

And lasers in general.

https://www.repairfaq.org/sam/laserfaq.htm#faqtoc