Author Topic: Laser Alignment/Repairs/Designs Resources  (Read 1324 times)

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Offline niflheimr (OP)

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Laser Alignment/Repairs/Designs Resources
« on: November 10, 2012, 09:56:12 AM »
TL;DR version : If you need help aligning or doing anything with a laser , check the articles here : http://www.repairfaq.org/sam/laseratr.htm#atrail

A couple of weeks ago I did a post about me wrecking a very expensive PSU and nearly wacking out a 20k $ laser assembly on a nearby table . Since then I spent two weekends working on getting the damned thing back in proper alignment.

The beast (that we use about as often as a raincoat in Sahara ) is an almost 20 years old argon pumped Sapphire:Ti that used to be maintained by another grad student . But since that guy found greener grass and emigrated to Canada ( Not that I blame him , I intend to do that as soon as I finish my EngD as well , since I just spent half my monthly income on groceries - research work here in Romania is paid less than sweeping streets) some helpful teacher at my uni decided that I should take his place.

Now , I do know this and that about gas lasers but the damned things almost got me to the point of wacking it with a hammer and hoping it will work then. After the cooling line misshap and replacing the fuse on its PSU ( 400V @ up to 30 amps) everything seemed ok - until I popped the cover on the argon and noticed the fine spray of water ran the dust and dirt from the covers on the mirrors .

Three hours later I had the HR and OC mirrors ( back and front mirrors for those that don't know how it looks like , here's a picture of a similar laser - the mirrors are mounted between the two mounting plates at either ends http://technology.niagarac.on.ca/staff/mcsele/lasers/images/ArLaserRepumpValve.jpg ) back in and was trying to realign them . With only a green laser pointer to help me with.

I spent a weekend going over it - it was only the second time I did this , and the first time I had a friend who's really into all this help me with . The result ? Zit , none , ziltch. No matter how I wiggled them I wasn't able to get the tube to lase - not to mention aligning it with the second stage . A few phone calls later and that friend , who was enjoying his holiday in Spain
(damned leech , he always knew how to earn more money than me :)) ) told me to check the link I first posted. And behold , one weekend later I had a nice blue-white beam coming out of the infernal machine.

And not only was it working , I was actually getting - if my meter is any good - almost 400mW worth of power. Back when I last got the urge to check it would peak at 200-ish mW.

Aligning it with the second stage was surprisingly easy though - took less than two hours.

So after two weekends of work I actually got the thing to work - and even better than before . I didn't had the inspiration to get some photos since I didn't had my camera with me (laugh all you want , I still have a 6 years old phone ) but the engineering of the tube is impressive. It's based on a comercial british design and it's more rugged than a soviet battle tank. I'm not surprised it's still working after more than 20 years.

One word of caution though - the supply is lethal if you touch the wrong parts and the cooling fan - well , I have a slice of my thumb missing. I bet you can slice sausages with that fan.