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FrozenGate by Avery

CNI 473nm DPSS: Alignment help needed

CurtisOliver

CurtisOliver

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I was just wondering if anyone could put me at ease.
A while back I purchased a 473nm DPSS of Styropyro. It is a 300mW system and has a peak of 320mW recorded by Styropyro himself. But before he sold it to me he said it was outputting less than that, and then decided to sell it for less. When I ran it for the first time, I discovered that it was still outputting well and it LPM'd at 247mW although there was some clipping going on. I noticed that the laser was hitting the edge of the aperture slightly.

Today, I decided to actually take a look at the insides of the laser. Part for curiosity and part to try and figure out why. :p It didn't take long to see why the laser is clipping the aperture.
The crystal plate is fixed wonky making the beam tracking slightly off to the side.
Now I didn't just want to start readjusting that plate without checking that it wouldn't pose any other alignment issues. What do you think?

Here's the internals when on. The laser was too bright for my phone camera, but when on you can see that the dot touches the internal hole as well.

CNI_473_13.jpg


Here is the beam profile.

CNI_473_2.jpg


Another internal shot:

CNI_473_11.jpg


And a couple with the laser off. I thought these might be nice to add for those who want to know what a DPSS Blue looks like on the inside. :)

CNI_473_14.jpg

CNI_473_15.jpg

CNI_473_12.jpg
 





I can only add this, I was pushing on that crystal assembly too hard on one of those assemblies and it popped off the TEC. I tried to get it aligned by hand and it is sensitive as hell to get right. However, that is sliding the whole aluminium "U" holder around on the TEC, should be easier moving with the screws slightly loose, but really is sensitive to the touch.
 
The crystal set/cavity optics are all one fixed unit, so you can loosen the screws holding that in and adjust it. That doesn't affect alignment of the cavity optics themselves, it does however result in the pump beam being misaligned. You will need to adjust the pump beam alignment if you adjust the cavity. May be able to just adjust the pump beam focusing lens (mount between the pump and the cavity), although it looks shimmed/glued pretty well as is...

Keep in mind LBO is hygroscopic. May be worth throwing in a fresh silica gel pack after you're done :)
 
diachi is saying what I'm thinking too, those four screws hold the whole thing, there is enough wiggle room to align it, but the glue on top of those screw heads might be a beast, if that is what it is, can't quite tell.

Whatever the thin white glue is they are using to hold that aluminium channel with the crystal down to the TEC with, it is aged.
 
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Alaskan said:
I should have mentioned this, what ever the thin white glue is they are using to hold that aluminium channel with the crystal down to the TEC with, it is aged and can pop off fairly easily, careful! But diachi is saying what I'm thinking too, those four screws hold the whole thing, there is enough wiggle room to align it, but the glue on top of those screw heads might be a beast, if that is what it is, can't quite tell.
Click to expand...


Setup is exactly the same as the B&WTek units that don't have the correction optics. If those are anything to go by the glue on the screws comes off pretty easy.

Have it on the LPM while you align it Curtis, easiest to peak the power that way.

You might want to check the LD is healthy if you can't get it back up to power. That or attempt some temperature tuning.
 
Just be sure your in a good mood before you start : D , Been there with a CNI 532nm and that was a lot of fiddling around .
 
Thank you Diachi and Alaskan. One thing I know about Styropyro is that he was a tinkerer. I'm wondering whether he at one point shifted that plate himself.
I was thinking that the pump diode may have to be aligned up again, but what if it is already slightly misaligned, hence the lower output plus the clipping?
Probably not knowing my luck. :p
What I was thinking about doing was marking out the plates current position, and then slightly angling it. If it makes things worse, then I have a reference to put the plate back. Or is this still a bit risky.
Also, I limited the exposure of the LBO as best I could. :beer:

Edit: My LPM is out of order ATM. :(

DashApple, I know what you mean. :D
 
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What diachi said.

Looks like CNI just did a sloppy/wacky job of it originally, on the surface, but maybe that is what they needed to do to get it to work--is hard to tell?
The anti tamper/glue material n the screws does not look distrubed at all.

The crystal set unit alignment looks to be adjusted pretty far over to one side on the apature side--not sure if the is much adjustment possible left.

The pump beam lens alignment might be the one to try adjusting to hit the middle of the crystal if it isn't---hard to tell really from the pictures/could be the pnotos are not showing the relationships accurately due to angle they were taken at??
 
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Syro has a video on that unit and said he realigned everything in it.
 
Thanks Encap, I'm thinking that while the laser is operating well at 250mW I shouldn't push my luck too much realigning it. If I can, i'll try and get some better images tomorrow. It is not easy getting the aperture in shot without it becoming one huge blue blob. :p

Alaskan, are you sure it was this one? I remember him fixing up a broken lower power unit before.
 
I didn't know he had another one... I went looking, you are correct, the other was 50 mw out, once adjusted.
 
Be careful when playing with the alignment on those b and w tek 473s! It just take a little to knock it out of alignment and its a bitch to get it back. I got one a while back for jmillerdoc and I still have not gotten it to lase 473 yet. They are very touce and do not like being fiddled with. With that being said good luck
 
Thanks Vortish. I might leave it be, as the last thing I want to do is go from a nice high output to none. :undecided:
I knew 473’s were harder than 532’s but still. Something so simple in concept as lining up the beam with the aperture could end up being a royal pita.

Thanks Alex. :)

I’ll take another look today and see if I missed something that I could do and then I’ll get some feedback.

:thanks:
 
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