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LIGHT BLUE 473nm repairs?

lisdexia

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Aligning the crystals is a difficult task. It requires a lot of patience and fine tuning. There are members on here that have done the job of realigning, and would probably be more than happy to guide you through it. But first it important to understand what the crystals are and how your laser actually works. As you know, the 473 is a dpss. You've already identified that there is a pump diode which will be at 808nm. Next there will be a Nd:YAG crystal that when pumped by the 808, will produce the 946nm line. Lastly you have a NLO crystal, which will frequency double the 946nm to produce 473nm. The NLO has very strict phase matching to comply with otherwise you will get no or very little 473nm output. The problem is we don't know if any of the crystals are damaged or if it is the crystals at all. If the pump diode is not outputting enough then the lasing threshold will not be met for the 473nm to occur. I own a 473 myself, but have never had to realign the crystals.


HOLY SHIT BATMAN :) so in my observations ive only seen 1 rod, would they above mentioned possibly be combined into one ??? .. if people are giving advice id be keen to try the alignment . crosses fingers that the rod isnt broken .. would it be advisable to attempt replacing the unknown value 808 c mount diode first before trying to manipulate the rod?
 
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CurtisOliver

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Do you have a picture of inside the laser head? (Crystals visible)
 
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CurtisOliver

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Ok, so only one crystal is actually visible. The other is embedded. By the looks of the scale of that crystal, that is most likely the Nd:YAG. And in front of it is where the NLO crystal lives. Whilst off, can you take a picture of the front of the crystal assembly?
 

lisdexia

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heres 3 shots of the rod .. in one with tweezers im pointing to a cloudy section of rod that appears completely different to the other 75% my concearn of that division is its not at 90 degrees it looks curved . not a clean joint ,
 

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CurtisOliver

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I'm no expert, but that cloudy area doesn't look normal. The NLO looks like it is in that front section. So there is no reason for any partition.
Does anyone here with more experience want to chime in? Surely the crystal shouldn't be cloudy on one end. I'm wondering whether it is either thermal/moisture damage?
The thing is if it is cloudy it will be diffusing the 946 beam hence no reasonable output for the NLO crystal.
 

lisdexia

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well that explains a bit .. next question i guess is there anything worthwhile to do with this unit ??? exchane rods ? colours ?
 

CurtisOliver

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Well, best to wait and see if anyone else has anything useful to contribute. I'm not ruling out the fact that I could of judged the clouding wrong. It makes sense. It is not as simple as just exchanging the crystal unless you get every spec spot on. Also changing the colour would require a complete overhaul on the crystals and optics.
I hope that something can be done, as that is lovely 473 unit you have.
 

CurtisOliver

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Great thread, joined due to it.
I'm glad you like the thread. :) I recommend that you make an introduction in the welcome section so everyone can welcome you properly. As you're here ... Welcome to the forum Plasmajuice. :p
 

CurtisOliver

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I can gather that they are quite common in more powerful units. You are getting quite a collection of optics and parts, so I'm not surprised that you have some of those mounts. :p
 

Alaskan

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Bought them from a guy in Ukraine along with ND:YAG's coated for IR to produce SHG 473nm out of a NL crystal, but the YAG's are not mounted in a copper mount like that and are side pump YAG's.

This is what he told me about them:

Sending 4 rods in boxes marked Northrop Grumman Synoptics YAG:Nd rods 3mmx45mm with flats on both sides as well as 473nm YAG assemblies you were asking before.

YAG's are broad band BBAR means they should be good for the whole lasing range 946-1322nm. Technically, instead of generators, you can use them as amplifiers to increase the power of your lasing assembly (including 946nm crystal set). In such a case you need to place the rod between YAG disk with HR mirror and your KNbO3 doubler. The pumping of rod should be individual from the sides. Such cavity is applied in JDSU high power lasers.
 
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CurtisOliver

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If they are side pumped then that explains why. The 473 in this thread is end pumped which is why they are using that type of mount.

Edit: Interesting that you have them BBAR coated. I haven't seen them being used as amplifiers before only generators.
 
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Alaskan

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More info on the stuff I bought:

The concentration of Nd3+ is 1.1% in garnet. The rods are capable of 30-40W CW main line multimode output with laser diode pumping.
The blue line frequency doubled 473nm laser cavity has YAG:Nd crystal (2mm clear aperture) with deposited mirrors HR946nm/AR808 flat/flat from one side and optical coupler HR946/AR473nm CC/CX from the other side. There is a space inside cavity for crystal doubler (13mm max length). The assembly has also embedded thermistor for temperature control.
 




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