sutable adhesive for gluing optics

[dave]

Today whilst working on other stuff, i decided to get the 1st laser we bought fixed, and perhaps push it back in to service.

Its a 150mw lambda pro, that we paid close to $2000 dollars for many many years ago.

Anyway, whats happened, is the glue holding the collimating lens at the front has given way... So i just need to glue it back on..

Would epoxy be ok for this? The lens is actually mounted in a small aluminum cylinder that has broken loose..

[JimBo]

I have used epoxy on mine.

Jim

[Zoof]

I've used epoxy on lense and aluminium and seems to work fine - don't know the long term effects though.

[JimBo]

You could also use a little bit of silicone instead.

Jim

[stanwax]

I too have used epoxy and also I am unsure of the longterm effects though its more likely to degrade if its inside the pump chamber and gets bathed in lots of scattered bright laser light. If its for the lens on the output it should do fine - plus if it lasts a couple of years before dropping off you can always stick it back on. Good thing with Epoxy is that there is minimal outgassing - which brings me nicely to Jims Silicone suggestion. I would NOT use silicone. A few years ago I sold a CNI green module to a guy who glued the complete module into a box with silicone. After a day or so the thing stopped lasing and when he reurned it to me all the adhesive used to mount the optics (ir filter, oc etc) had turned to a very soft powderery texture that could be easilly scraped away with your fingernail.
I exposed a spare part with an IR filter mounted on it to vinegar and overnight the same effect was seen.
The acetic acid liberated by the curing process had destroyed the (what I assume was uv cure) adhesive.

Just my 2p (actually with my verbal diarrhea its more like 50p)

Rob

[carmangary]

Seems like superglue would do the trick.

[stanwax]

Super glue is very bad as it liberates vapour while curing. This coats everything in the area with a dull Bloom. Unless you cover the optics beforehand its not a good idea.
I keep superglue a long way from any laser related stuff

Rob

[JimBo]

I think superglue also contracts over time, so the joint ends up failing.

Jim

[The_Doctor]

Some cyanoacrylates (superglues) have low outgassing, and if you use a small amount and keep good airflow during the initial cure, bloom will be minimal or absent. Take care to soak up uncured liquid exuded from the join, with the edge of a piece of paper sawn gently along the edge of the join. Blow gently past it as you do all this, and NOT at the actual optic surface. This makes a fast stream of air to carry any vapours away from the optics, as the pressure difference stops the vapour from moving toward their surfaces. If possible, use a tube, and plan your air path beforehand and practise to get the timing right. Not sure about long term use, but it should be ok, it forms an acrylic plastic. If you can shoot a couple of hundred mW of light through an acrylic asphere without degradation, I doubt a bit of spilled light will affect a cyanoacrylate glue join.

Ideally, use a UV cure epoxy, the white stuff that is normally used. I don't know what that costs though. I want to know soon, I intend to use it. Dental suppliers on eBay are good for cheap(ish) sources of cure lights of wavelengths many and diverse, but the goop itself I have yet to learn about. The really neat thing about UV cure is you can take time to optimise alignments, then set them in place quickly and easily.

I'd also avoid silicones, but check out things like Loctite's 'TempFlex', as that and some others might be suitable. Expensive though, might as well get UV cure stuff if Money is going to be Spent.


EDIT:
Interesting story about that acetic acid from silicone cure destroying a UV epoxy... Sounds to me like a bad choice of epoxy. While dental cements aren't formulated right for laser optics, they have to be highly resistant to acids when cured. There must be some glue that is resistant, AND good for optics.

[dave]

Epoxy it is then