Possible to rescue this 473nm DPSS? - total EBay fail

[MrMcChicken]

Hello everyone,
I have bought a 473nm DPSS from E-Bay and was really happy to receive it today. After playing around a bit I was wondering why I did not get any delicious 473nm light. I noticed something rattling, so I opened it up.
The following shocked me really hard. The pictures show what I have found. I realized that the module with the crystals was completely loose and shaking around. I have not touched anything at this moment. This laser was trashed this way when I got it.
Is there any way to rescue it? The coatings on the crystals look like they have seen better days. The 808nm diode seems to work. I have tested it with a YAG & KTP and got green 532nm out.

There is a short crystal in the aluminum part and a long crystal in the brass part. I don't know which crystal is which, but it seems the person who has ruined this laser didn't know either. I assume the small crystal is the YAG and the long is the LBO crystal. For some reason the LBO crystal was mounted in front of the 808nm laser diode and the YAG after the LBO. This makes no sense to me.

Is there any hope to rescue this thing? I assume that the LBO and the YAG have to be aligned correctly, but the overall alignment of the pump diode and the crystal pair is not that critical, right?

Here some pics. It is horrible!

 

[diachi]

You are correct about which crystal is which, short one is YAG, long one is LBO. Keep the LBO sealed up in a dry environment (ideally with desiccant present to keep the air dry). LBO is hygroscopic. DO NOT touch the crystal faces. Keeping them free of any contaminants is important. Best case you need to clean them, or you end up with sub-par performance. Worst case you cook them.

Pump alignment and crystal alignment are both important. You can have the crystals/cavity aligned but get good lasing (or perhaps any) until the pump is aligned too.

Can you grab some more pictures for us and then link to the full size versions? One looking through each crystal at a light source, that'll help us identify cracks. Another looking at the crystal faces with light reflecting off, that'll help us see if they are coated and what condition the coatings are in.

A link to a full size version of what you already posted would be useful too. I don't see any external optics, but I could be missing something.

 

[paul1598419]

If you bought this on eBay, did you buy it "as is"? If it was sold as working you should be able to get your money back from PayPal. That is a better choice than trying to make this abused unit work again. Someone else has probably had their hands all over any part of the crystals that aren't covered well. The alignment of one in good shape could be a challenge.

 

[Alaskan]

Alignment of the pump diode to the crystal module is critical, but something you can get right without a terrible amount of trouble, I wouldn't worry about that. One thing though, in the photo of the LBO or the long crystal, why does it appear to have a pattern on top of the crystal, is that a thin sheet of foil?

 

[ZRaffleticket]

See I was wondering what that was too... I'm worried more about it being water damage/residue left by water

Though now that you say that it does look more like metal

 

[diachi]

Alignment of the pump diode to the crystal module is critical, but something you can get right without a terrible amount of trouble, I wouldn't worry about that. One thing though, in the photo of the LBO or the long crystal, why does it appear to have a pattern on top of the crystal, is that a thin sheet of foil?

It's probably indium foil. Looks like it to me. Indium makes a good thermal interface material for laser crystals. It's soft but also provides good heat conduction. You want the interface material to be soft so that it doesn't damage the xtal.

See I was wondering what that was too... I'm worried more about it being water damage/residue left by water

Though now that you say that it does look more like metal

It takes a while for LBO to be damaged by moisture in the air, but best avoid it anyway.

 

[Alaskan]

It looked like Indium foil to me too, but other than to help seal the crystal surface, I don't know why there would be some on top. Maybe the whole crystal is wrapped in it.

E: I see now, went and looked again, the whole crystal is wrapped in Indium foil, that's why.

 

[MrMcChicken]

I have taken some photos of the LBO crystal and re-uploaded the previous pictures in higher resolution. The faces look really bad. I have taken one from the YAG too, but it is hard to reach. The LBO was wrapped in aluminum foil. There were no lenses or any other optics inside it.

The laser cost me about 50 bucks, so I am not sure what I had to expect.

If it is possible to do something with these crystals I will 3d print some mounts and see if I can get at least a few mW out of it.
The pictures are not embedded here because they are quite big. I had to host some pictures via a different hoster because I had some
problems in uploading them. I hope it is okay.

Previous pictures:
http://fs1.directupload.net/images/171210/6wq3xua3.jpg
http://fs5.directupload.net/images/171210/sceldbop.jpg
http://fs1.directupload.net/images/171210/wkqhpdgv.jpg
http://fs1.directupload.net/images/171210/n7rvtczg.jpg

LBO:
https://imgur.com/a/0Fljh

 

[diachi]

I have taken some photos of the LBO crystal and re-uploaded the previous pictures in higher resolution. The faces look really bad. I have taken one from the YAG too, but it is hard to reach. The LBO was wrapped in aluminum foil. There were no lenses or any other optics inside it.

The laser cost me about 50 bucks, so I am not sure what I had to expect.

If it is possible to do something with these crystals I will 3d print some mounts and see if I can get at least a few mW out of it.
The pictures are not embedded here because they are quite big. I had to host some pictures via a different hoster because I had some
problems in uploading them. I hope it is okay.

Previous pictures:
http://fs1.directupload.net/images/171210/6wq3xua3.jpg
http://fs5.directupload.net/images/171210/sceldbop.jpg
http://fs1.directupload.net/images/171210/wkqhpdgv.jpg
http://fs1.directupload.net/images/171210/n7rvtczg.jpg

LBO:
https://imgur.com/a/0Fljh

Well, I don't see any cracks in either crystal, so that's good. That said, the coatings on the LBO don't look good. Can't see the coatings on the YAG so can't comment there.

Don't see any sign of external mirrors, the mirrors are probably on the xtals which means you need the coatings to be good seeing as those are your mirrors.

That makes alignment somewhat more difficult too. Without a proper jig or adjustable mounts it's going to be a pain.

I'd probably blame those coatings for the lack of lasing though. Probably not going to rescue it, but at the least it makes for a good DIY DPSS platform.

 

[MrMcChicken]

Thanks for the responses. Is there any way to use those crystals? I assume that the YAG has similar damages.
Has the LBO to be between mirrors to work? I always thought it just has AR coatings and converts the 1064nm light
without being and optical resonator.
Would it be possible to use a 1064nm pulse laser to pump energy pulses into the LBO? The energy density would be a lot higher
and I don't know if the LBO does survive such abuse.

Edit: looked it up, will need mirrors. Sorry for the garbage i postet above.

I have looked for services to do coatings, but they are just to expensive.

 

[Alaskan]

I'm wondering if these units on ebay use the same crystal assembly: https://www.ebay.com/itm/Blue-Light-473nm-Laser-optical-assembly/162777021641

Look at this thread to see some photo's of the crystal assembly used in the above listing: https://laserpointerforums.com/f42/b-wtech-473nm-unit-spectrometer-mods-info-101467.html

 

[diachi]

Thanks for the responses. Is there any way to use those crystals? I assume that the YAG has similar damages.
Has the LBO to be between mirrors to work? I always thought it just has AR coatings and converts the 1064nm light
without being and optical resonator.
Would it be possible to use a 1064nm pulse laser to pump energy pulses into the LBO? The energy density would be a lot higher
and I don't know if the LBO does survive such abuse.

Edit: looked it up, will need mirrors. Sorry for the garbage i postet above.

I have looked for services to do coatings, but they are just to expensive.

It's 473nm, so it's using 946nm, not 1064nm.

Frequency doubling can be done without the xtal being inside of the resonator, but it requires huge amounts of power. Frequency doubling is a non-linear process that becomes more efficient as input power increases. Lots of power available inside the cavity, which is why an intracavity doubler is often used.

Getting those optics re-coated would be very expensive, if it's even possible to do it properly. Cheaper just to find replacement xtals on eBay.

I'm wondering if these units on ebay use the same crystal assembly: https://www.ebay.com/itm/Blue-Light-...y/162777021641

Look at this thread to see some photo's of the crystal assembly used in the above listing: https://laserpointerforums.com/f42/b...fo-101467.html

Might be similar, but one big difference is that those units use an external OC, at least as far as I've seen.