Mystery Wavelength in PMS/REO Particle Counter Tube

Hi there, so I got this unit a while back hoping it was a single Brewster tube particle counter. Alas it twas not the case. However I did notice a wavelength in the output that shouldn't have been there.

This thread is meant as documentation for anyone looking at particle counters and as mystery thread that I hope someone can solve.

This is the model number on the unit:


This is the tube that came out of it:


And the optical set up inside:




I don't understand the point of it but here is the output, post optics:


The tube has a ghost beam out either end that is fairly bright and it doesn't appear to be an alignment issue. Must be a mistake or a intended effect.


Finally the weird extra line (through a diffraction grating):

I tried to measure it on my own with a diffraction grating but my math keeps coming up nonsense. I suspect it is 640nm or 650nm, but I have no way of telling....

Any ideas?

That's just a ghost beam as an artifact of the mirror setup, and is perfectly normal. Wavelength is the same as the main beam.

I don't think so, it has it's own mode structure and alternates between TEM 00 up to TEM 03 then dies. Then it comes right back.

Anyone have ideas? It is clearly not part of the ghost beam, but I still don't know what it is.

There are several other red lines... It could be any number of them. There is a line at 640.1nm that is relatively easy to get so it's quite possible. Most old Brewster tubes are all soft seal. Nowadays they just do a kind if photomultiplying array, as it's much cheaper and more conventional, and far easier.

OK, I will try to get a better set up to measure the wavelengths. I think I messed up the measurement the first time.

You're probably right as that's the easiest of the other ones to get. Especially if not using a lab grating

Its not difficult to envision a REO Particle Measurement tube to emit multiple lines. I have one of the three mirror ones doing 18 lines if you count the IR lines and the very weak 4 wave mixing lines. I've verified they are lasing by detuning the third mirror and they are NOT grating ghosts.

I'm about to sell three of the tubes that do multiple visible lines.

Steve

LSRFAQ said:

I'm about to sell three of the tubes that do multiple visible lines.

Steve

Click to expand...

I would be very interested in one of these especially if there is orange.

Where would you be selling them?

TheGreaterWatt said:

I would be very interested in one of these especially if there is orange.

Where would you be selling them?

Click to expand...

Ditto. I enjoy REO tubes thoroughly.

Bit late, but I had the opportunity to handle one of the aforementioned REO PMS heads. The third of these that I've seen the output of. I don't recall a single one not doing AT LEAST one orange line.

I've seen some even dip into the yellow. The laser you see in my sig titled "REO particle counter" (something like that, on mobile) does many lines. As, also, seen in the sig.

These are great examples of the multi line capabilities of the HeNe, and gas lasers alike.

PS - Extra fun fact. These use 3 mirrors to get multiline output. Two sealed mirrors for HIGH output (multimode) 632.8nm. The precise alignment of an additional mirror (and polarization optics) results in the multiline output.

These are fascinating animals of the gas laser world.

bloompyle said:

Bit late, but I had the opportunity to handle one of the aforementioned REO PMS heads. The third of these that I've seen the output of. I don't recall a single one not doing AT LEAST one orange line.

I've seen some even dip into the yellow. The laser you see in my sig titled "REO particle counter" (something like that, on mobile) does many lines. As, also, seen in the sig.

These are great examples of the multi line capabilities of the HeNe, and gas lasers alike.

PS - Extra fun fact. These use 3 mirrors to get multiline output. Two sealed mirrors for HIGH output (multimode) 632.8nm. The precise alignment of an additional mirror (and polarization optics) results in the multiline output.

These are fascinating animals of the gas laser world.

Click to expand...

Thanks bloom!

I have been on the hunt for a 3 mirror particle counter tube for a while. And when I find one for a decent price I will be sure to snag it