Multiline green pointer. How is this possible?

So here are two ways I would usually see the spectrum of a light source: diffraction and spectrometer.








There is one wavelength on this pointer - 532nm as you might expect. However, this particular transformable pointer from O-Like exhibits some stranger readings.





There are two additional lines at about 537nm, and 542nm. I've never heard of a 1074nm or 1085nm Nd lines. How is this possible??

Bump for this thread.

For the picture with the three dots, is the beam passing through the diffraction grating as well?
My first thought was that it looks like internal reflection from a prism.

I'm a little jealous, I admit.
Both for the spectrometer and the "multiline" DPSS mystery greenie.
I hope you know the answer and are holding out on us.

Maybe (and dunno why) u got a Yb dopant instead of a Nd one...

It also occurs to me Raman scattering or Brillouin scattering...


But im not a laser expert, so dont take too much consideration on my thoughts...


*edit* and its more 543 rather than 542...minor reading correction...doesnt affect much everything...and im also not very keen with the Yb dopand explanation

Actually, look what i found:

>>check it out<<


*edit* for those that dont want to read:
...
With 590 mW diode pump power, a continuous-wave (cw) SHG output power of 19 mW at 542 nm yellow–green color has been obtained using a 1.5 mm-thick BIBO crystal. The optical conversion efficiency was 3.22%. It was found that the output wavelength could be 532 nm, 537 nm or 542 nm according to regulating the angle of BIBO.
...

RA_pierce said:

is the beam passing through the diffraction grating as well?

Click to expand...

Yes

RA_pierce said:

I hope you know the answer and are holding out on us.

Click to expand...

I honestly have NO idea what's going on.

LordKaramazov said:

>>check it out<<

Click to expand...

That's interesting, but it doesn't quite explain why it's happening with a KTP instead of bibo, and all three at once.

Well, what could be happening is that there's some other dopant in the crystal. The Chinese aren't exactly the best with their quality control, and, well, other 'stuff' (often with their own transitions) makes their way into the vanadate along with the intended neodymium.

At such low powers, they wouldn't need to be particularly absorbant at the pump wavelength, energy transfers can occur between Nd atoms and other rare-earth dopants.

But either way, I'm surprised they're lasing at all. With a but of luck (and crapshooting), KTP can double something that's not 532nm, but not very efficiently.

If you're game enough, you may want to disassemble it, and place a glass slide as a beamsplitter intracavity, and take some readings with the spectrometer from within the cavity.

And if it ever does drop dead on you, you should probably get the composition of the vanadate and KTP analysed, I'm guessing it's not too pure at all.

actually, and strangely, i just brought home today a Wiley Laser and Photonics Reviews magazine from january 2010.

Guess what, in the 5 or 6 review articles in the magazine one of them concerns BIBO as a non linear frequency conversion crystal and that article is included in the review.

Maybe BIBO is cheaper than KTP and now they are taking advantage of that...maybe we will start to see greenies with BIBO...whats strange is the effiency they claim for the 542 line...i guess u dont have a 200W pump on that, or do u? xD (just throwing numbers to the air dunno what kind of laser is that)

but if u want i can read it (right now i cant...im in exam period and i cant distract myself with that huuuge article) and try to explain it...


*edit* @goninab00d The BIBO SHG lands spot on the frequencies they speak....and the different dopand doesnt seem a reasonable explanation or even using Vanadate instead of YAG (as YVO4 has a bigger gainband) doesnt seem very much reasonable (YVO4 gets a band 0.94nm wide for the 1064nm lasing transition) and so it wouldnt get the 2.5+2.5nm needed for the +5=537 and +5=542 SHG.

Id bet more in a kind of effect more like the one as BIBO with a strange efficiency though...

maybe searching for more articles but KTP related...

I don't see how that would be possible. The crystals are fused together, aren't they?

It is a little under spec. putting out 35-40 (including slight 804nm pump leak) instead of the rated 50mW.

yeah, think they are kind of "glued" together, yes!

that is a strange little laser u got there

I'm not talking about the Nd:YVO4 being 'tuned'.

I'm saying there may be impurities within the YVO4 structure, that, as a result of energy transfers between the Nd+ ions and the respective rare-earth metal ions, are causing them to lase.

The optical coatings on the faces of the KTP and YVO4 would easily cover up to 540 and 1080nm, without any issues. Have enough crap in there, and you could very easily promote lasing in the other atoms.

KTP can be used to double something other than 532nm, just not very well. And given the efficiencies, I wouldn't be surprised if that was the case.

Cyparagon -- are the other two dots visibly different ? I'd assume they have to be.. 543 is quite a bit visibly different than 532...

Yes. I'm not sure how much of it is 'placebo', but I see a very slight difference in color. It'll be difficult, but maybe later I'll try to capture the color difference.

http://www.patents.com/us-7088760.html

However, when an excitation power is increased in order to obtain a high output power in the conventional solid-state laser apparatuses having an etalon in a resonator, oscillation of undesired wavelengths occurs at the same time as oscillation of a desired wavelength. For example, in a solid-state laser apparatus, when laser light having a wavelength of 1,064 nm is desired, oscillation of laser light having wavelengths of 1,075 nm and 1,085 nm occurs concurrently.

Click to expand...

What happens if we half the 1075nm and 1085nm lines? 537.5nm and 542.5nm!

:wave:

sorry for the old thread. We were talking about another similar thread in laserchat, and we came across this link which matched up too nicely with the spectrographic analysis in the OP.