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FrozenGate by Avery

KTP and DPSS






Yes, that's a great thread, I remember it. Your statement is partially accurate actually if you're talking about direct doubling.. but KTPs unsuitability for that doesn't have anything to do with the KTP being made for a specific wavelength. It's good for any wavelength across a small swath of spectrum.

Direct doubling is a whole different ballgame than normal DPSS. It's not even really DPSS at all.. DPSS uses a laser crystal in conjunction with a non-linear crystal. This is important because of the beam specs and power density generated by laser crystals as opposed to laser diodes.. Since the problem is with the beam quality of laser diodes that are powerful enough to get doubled output and not reflections, an AR coating won't allow for direct doubling a laser diode by itself.
 
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Apart from ND:YAG and ND:YVO4, are there obtainable crystals that would produce strong lines in the 1000 to 1200nm range?
 
It might be neat to research Third Harmonic Generation using the 1440nm ND:Yag line.

If it's possible, I'm sure someone has tried. I'll take a look through some databases later today. What do you use instead of KTP to do THG?

If you look at the diagram on CNI's 355nm page, it makes it look like you can do THG with a prism. 355nm UV Ultraviolet laser.
 
rhd said:
If you look at the diagram on CNI's 355nm page, it makes it look like you can do THG with a prism. 355nm UV Ultraviolet laser.
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No. That diagram illustrates that the laser outputs three wavelengths:

1064nm because sometimes a photon doesn't collide with any others.
532nm because sometimes two 1064nm photons collide and combine.
355nm because sometimes a 532nm photon collides with a 1064nm photon.

These can then be split using a prism, like the multiline argon lasers we all know and love.

593.5nm DPSS lasers are also known to do this, though to a lesser degree. You can only really see it on a spectrometer.

Trevor
 
That occurred to me after I had posted.

It still implies that there is a component inside the laser capable of doing third harmonic generation.
 
rhd said:
That occurred to me after I had posted.

It still implies that there is a component inside the laser capable of doing third harmonic generation.
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Probably LBO or BBO.

Trevor
 
rhd said:
It might be neat to research Third Harmonic Generation using the 1440nm ND:Yag line.

If it's possible, I'm sure someone has tried. I'll take a look through some databases later today. What do you use instead of KTP to do THG?

If you look at the diagram on CNI's 355nm page, it makes it look like you can do THG with a prism. 355nm UV Ultraviolet laser.
Click to expand...


THG to 355nm is most commonly done with 2 non-linear optics. One doubles 1064 to 532, the next sums the previously doubled output with the leftover 1064nm from the laser crystal to make 355nm. Both functions can technically be performed using KTP, but since ultimately the output will be below 500nm it's not possible to use it as the summing optic in this case. Given the wavelength LBO would be a good choice for summing but there are other choices as well..

The math:

Doubling: 1064/2 = 532

Summing: (1/1064)+(1/532)= .00282 Then we invert: (1/.00282) = 354.609 or 355nm

Trevor has already pointed out the similarity to 594nm yellow lasers. This is due to the fact that 594nm yellow lasers use summing to produce yellow. Since there is no doubling optic first, 594nm yellow is not an example of THG.
 
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ElektroFreak said:
Trevor has already pointed out the similarity to 594nm yellow lasers. This is due to the fact that 594nm yellow lasers use summing to produce yellow. Since there is no doubling optic first, 594nm yellow is not an example of THG.
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Indeed. I cited that to illustrate the randomness of SFG - sometimes you get a pair of 1342nm photons combining to get 671, sometimes you get 2 1064nm photons for 532nm.

But the process is optimized for 1064nm + 1342nm = 593.5nm, so that one dominates. But you still can see the other wavelengths on a spectrometer.

I really wish we had the capacity to build this sort of thing. D:

Trevor
 
Trevor said:
Indeed. I cited that to illustrate the randomness of SFG - sometimes you get a pair of 1342nm photons combining to get 671, sometimes you get 2 1064nm photons for 532nm.
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I can't find anything but 589nm in my yellow pen. Any idea why?
 
Cyparagon said:
I can't find anything but 589nm in my yellow pen. Any idea why?
Click to expand...

If I had to guess I'd say it's just newer, better technology. 593.5nm pens used to have bad habits of being green a few years ago, but I've not heard of that happening recently.

Trevor
 
Cyparagon said:
I can't find anything but 589nm in my yellow pen. Any idea why?
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I'm not 100% sure how 589nm is generated, I haven't really tried too hard to find out actually. I have to assume that it's a different process than 594nm because 589nm lasers tend to be much more powerful than 594 in the same size packages, so whatever system is used it's much more efficient.
 
While doing some quick research I ran across this little tidbit:

http://cpl.iphy.ac.cn/qikan/manage/wenzhang/0232095.pdf

Due to the efficiency, I highly suspect that doubling is the method used for 589nm, but that means that there would have to be an incoming beam at 1178nm. The above paper on a 1178nm raman laser shows a simple linear cavity and uses Nd:YVO4.. abundant and cheap. This is the kind of thing that's needed to create pointers and most of the lab-style heads we're used to as hobbyists.. you won't find complex cavities in pointers. The design in the paper uses an AOM since it's q-switched, which would allow for extra-cavity doubling, but I think that a normal intracavity design would have enough power density in the cavity for doubling to 589nm.

Give the cost and efficiency of 589nm, IMO it would HAVE to use fairly readily available crystals.. couldn't be anything too exotic.
 
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ElektroFreak said:
While doing some quick research I ran across this little tidbit:

http://cpl.iphy.ac.cn/qikan/manage/wenzhang/0232095.pdf

Due to the efficiency, I highly suspect that doubling is the method used for 589nm, but that means that there would have to be an incoming beam at 1178nm. The above paper on a 1178nm raman laser shows a simple linear cavity and uses Nd:YVO4.. abundant and cheap. This is the kind of thing that's needed to create pointers and most of the lab-style heads we're used to as hobbyists.. you won't find complex cavities in pointers. The design in the paper uses an AOM since it's q-switched, which would allow for extra-cavity doubling, but I think that a normal intracavity design would have enough power density in the cavity for doubling to 589nm.
Click to expand...

Uhhh, isn't 589 just 1,064 and 1,319 summed? That's what I assumed.
 
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It could be, I had considered that awhile back but Nd:YAG is notoriously finicky compared to Nd:YVO4, which is why the vast majority of green lasers now use YVO4. 473nm is generated by doubling Nd:YAG, and it's fairly stable but highly inefficient.. The 1319nm line in YAG isn't as strong as the 946nm line as I recall and neither is nearly as strong as the obvious 1064nm line.

Plus there's the timing of their appearance.. 594nm lasers were around in hobbyist hands for a good while before 589nm became popular, and it became popular due to the higher powers over 594nm that are possible. I see a technological development there, something became practical with common components that wasn't previously. 594nm is a very inefficient process, as is 473nm generation. For summing Nd:YAG to be used for 589nm would surprise me a little, but it's not impossible. To me 589nm has YVO4 written all over it.. certainly could be wrong though.
 
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