780 nm instead of 808 nm ?

[robi500]

What would be the result if you would put 780 nm IR laser diode instead of 808 nm IR laser diode into the green laser module?

:thinking:

 

[anselm]

Hello and welcome to the LPF!

Regarding your question: it wouldn't work.
The crystal pair in green DPSS lasers that converts IR light into 532nm green needs
to be pumped by 808nm IR, not 780nm.

 

[robi500]

Hello and welcome to the LPF!

Regarding your question: it wouldn't work.
The crystal pair in green DPSS lasers that converts IR light into 532nm green needs
to be pumped by 808nm IR, not 780nm.

I thought that it would work like this :

808nm-Nd:YVO4(*1.3168316...)=1064 nm-KTP (1/2)=532nm


780nm-Nd:YVO4(*1.3168316...)=1027,12871...nm-KTP(1/2)=513,5643nm

 

[Grix]

Hello and welcome to the LPF!

Regarding your question: it wouldn't work.
The crystal pair in green DPSS lasers that converts IR light into 532nm green needs
to be pumped by 808nm IR, not 780nm.

Are you sure? Remember diodes fluctuate quite a lot in terms of wavelength. If you have a freak 808 diode that outputs 800-780nm.. Would that ruin the DPSS process?
If yes, what is the lowest possible wavelength that can be used to pump greenie crystals?

I thought that it would work like this :

808 nm-Nd:YVO4(*1.3168316...)=1064 nm-KTP (1/2)=532nm


780nm-Nd:YVO4(*1.3168316...)=1027,12871...nm-KTP(1/2)=513,5643nm

I do believe KTP can only frequenzy double to exactly 532nm (in green's case), so the Nd:YVO4 would have to lase at a constant wavelength unaffected by the pump diode's wavelength..

 

[anselm]

Well, to be honest, I am not absolutely sure, but I remember reading something like that.
Also, "freak" diodes vary within a few nm, not 20~30nm.

And yeah, when pump diodes get warm more than they should, they shift wavelenght
a little, and the green beam goes dim.

I thought that it would work like this :

808nm-Nd:YVO4(*1.3168316...)=1064 nm-KTP (1/2)=532nm


780nm-Nd:YVO4(*1.3168316...)=1027,12871...nm-KTP(1/2)=513,5643nm

Yeah, if that would work, I think we would have seen a 513nm laser here
or elsewhere, wouldn't we?

 

[Ash]

A 780nm diode through Nd:YVo4 --> KTP will still lase at 532nm:

Quote from Sam Goldwasser:
"If you pump Nd:YVO4 with 780 nm, the absorption is much lower. If it does lase,
it's still at 1,064 nm, just very weak."

 

[anselm]

Well I'll be damned!! Interesting...
So, practically, it doesn't really work in any useful manner...
Notice how he says :"If it does lase...."

 

[532 with Envy]

A 780nm diode through Nd:YVo4 --> KTP will still lase at 532nm:

Quote from Sam Goldwasser:
"If you pump Nd:YVO4 with 780 nm, the absorption is much lower. If it does lase,
it's still at 1,064 nm, just very weak."

This is interesting to hear...I too remember hearing that falling off the 808nm wavelength will keep you from lasing 532nm or perhaps 488(?)nm it was.

Quick question...what is the crystal coating for a 589-593nm wavelength, I figured that the yellow pointers from CNI and other companies where DPSS, but I haven't seen the crystals on the market for them.

PS...good thread for general DPSS knowledge.:beer:

 

[goninanbl00d]

Nd:YVO4 does have an absorption band at 780nm, although it is significantly lower than the one at 808nm.

It can (and will) lase when pumped with 780nm, but not nearly as efficiently as if pumped with 808nm.

The reason why the wavelength doesn't shift depending on pump wavelength is because the pump photon is absorbed by a neodymium atom. This atom (now in the excited state) emits a 1064nm photon in order to drop to a lower energy level state.

If gain media did change output wavelength based on input wavelength, lamp-pumped frequency-doubled YAGs would put out an interesting shade of baby-vomit green.

The reason why efficiency drops off as the pump wavelength shifts is because the pump wavelength begins to shift away from the absorption band of YVO4. A gain media may have more than one absorption band, but these bands are usually extremely narrow and require that the pump wavelength to be centred on these bands.

EDIT: @532 with Envy, the reason why you haven't seen them is because they're extremely hard to produce, and even harder for a hobbyist to use/align.

594.3nm uses YVO4 and KTP, however, in this case, a different non-linear optical process is used. The YVO4 lases at both 1064 and 1319 (or was it 1342?). This is then combined in the KTP to produce 594.3nm light.

589nm is a more traditional SHG process, but using proprietary gain media.

 

[532 with Envy]

EDIT: @532 with Envy, the reason why you haven't seen them is because they're extremely hard to produce, and even harder for a hobbyist to use/align.

594.3nm uses YVO4 and KTP, however, in this case, a different non-linear optical process is used. The YVO4 lases at both 1064 and 1319 (or was it 1342?). This is then combined in the KTP to produce 594.3nm light.

589nm is a more traditional SHG process, but using proprietary gain media.

Thank you very much for the concise answer. I kind of figured it was complicated and thus "expensive", but it's nice to get a clear, quick answer like this

 

[goninanbl00d]

Thank you very much for the concise answer. I kind of figured it was complicated and thus "expensive", but it's nice to get a clear, quick answer like this

That's why it's damn near impossible to find info on 589nm DPSS systems.

Whereas with 594.5nm, it's just a PITA to get working.