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604 nm artifact with 532nm dpss lasers

yveslafont

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Jan 28, 2009
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Hello, i'am working on a DIY Raman probe.
I have checked three 532nm lasers :
1) 532nm cheap laser pointer 1mw
2) 532nm 50$ laser pointer 5mw
3) 532nm 200$ laser module, from Thorlabs, 4.5mw

When i use my spectrometer (LR1 from Aseq), with any of this lasers, i can see that :
532 nm main wave
604 nm wave, around 1/20 of 532 nm power
800 nm wave, very low power

Using a 532nm bandpass filter, the 604 nm is still here, not very much atenuated.
I can't understand why this 604 nm have to be there ...
After i asked the spectromer brand, they reply the problem is the laser ... but, the three lasers shwo a 604nm wavelength
After i asked the laser brand, they reply the problem come from the spectrometer

It seem, after some experiments, the 604nm power is proportional to 532 nm power.

If someone still have see this problem, or have an idea, can you please, explain that ?
I join a screenshot .. MTest_cps532_raw.jpgy three lasers show that ...
Thank you very much !

Greetings,

Yves
 



kecked

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Jun 18, 2012
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I had a similar problem and it turned out to be fluorescence in a bad silicon fiber optic cable.
604 is also a raman line but not at 1/20 the power of the fundamental. More like 0.000001 the fundimental.
use an edge filter and see if you can see a beam or is it scattter. If you see a beam I have no idea.
try a different fiber
 

yveslafont

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I have same problem with all my fibers ( 50µm, 200µm, 400µm, 600µm).
I wait for an edge filter, in next days .. i Wait and will see ...
 

Cyparagon

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Since the power is relatively high, and in a visible band, you can use your eyeball (or camera) and a diffraction grating for a second opinion. Does the laser dot indeed have two wavelengths when viewed this way?
 

Seoul_lasers

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Last edited:

kecked

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Can you put the beam through a prism or onto a grating prior to the fiber. Then block the green beam as best you can and look for the orange. If it’s still there you might have something interesting.

I wonder if your getting harmonic mixing? If the 808 and1064 where somehow mixing to produce another ir line it might mix up to the 604 line your seeing. I know cni made such a laser on purpose. Guessing here
 

ZRaffleticket

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CNI's 604nm doesn't involve IR - That's one of the 445nm pumped Pr: doped crystals. I'm much more convinced of the fluorescence idea. See if the spike happens with other lasers, try a 520nm diode for example. Try to see if it's 532nm DPSS or not.

Though not dismissing the idea entirely, it is physically possible. Just very unlikely to happen on all three that were tested. 589 or 593.5 would be much more likely to get in that range since the coatings already work with strong lines that could get to ~604nm.
 




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