A long, long, time ago, I can still remember how that music, used to make me smile. And I knew if I had the chance, that I could make those people dance and maybe they'd be happy for a while....
Alright, I digressed into Don McLean's "American Pie". That was meant to start off
A long, long, time ago, I decided that it would be rather cool to build my own laser. Not one of these paltry 5mW deals, you understand. I wanted the real deal - 10W or more of output power! The easiest choice seemed to be to build a CO2 (Carbon dioxide) laser. So, around Jan 2003, I started construction!
Well, it's now October and I can finally try it out. My mirrors have arrived back from the coating company, and I've set up the cooling system, vacuum pump and neon sign transformer again. Fingers crossed!
This is really a "test" laser, just to see if the principle works. And indeed, at 1:30 pm on 1st Nov 2003, it did indeed work! For ½ second, and then the power supply shorted through the cooling water. It seems that water had leaked through a gap between the plasma tube and the rubber ring sealing it to the cooling tube.
This is the next step up from v1. An aluminium tube serves as the cooling jacket and support. The plasma tube is held coaxially with this by two machined plastic blocks that carry water, gas & electrical connections. A feature of this design is that only one of the mirrors (the full reflector) is adjustable; the output coupler is fixed. This allows the hole in the output coupler to be exactly located in the center of the tube, and it also makes it easier to align since the position of the output coupler can't change. You only have to worry about the position of the full reflector.
Okay, some disappointing news. Try as I might, I cannot prevent the NST shorting out through the aluminium tube or through the water jacket. Also, one of the O-rings burst and the vacuum pump is now full of water! Not very successful...
This uses the same plastic headstocks as v2 but they are mounted on a rack hanger instead of inside a metal tube. The cooling water is kept completely separate from the electrical stuff. At 3:00 pm on 6th December, it worked!
Well, sort of....it works for 1/2 second and then stops (sounds familiar?). But if you turn off the NST, wait 10 secs and turn it on again, it runs again! For 1/2 second and then stops. Etcetera...... So something is preventing it from continuing to lase. Will have to ask someone about this.
13 Dec 2003: If you drop the pressure to 10 Torr then the output becomes CW. There is still an intense pulse at switch-on (enough to burn wood) but then the output decreases but it is still there. Enough to turn thermal fax paper black!
Right, it's almost a year later (July 2004). I've decided to have a go at the laser again. Will use an extruded aluminium section as a base and proper ZnSe/Si mirrors. Day 1 is 24 July!
I'm currently hunting around for the cheapes supplier of CO2 resonator mirrors. Will post who I find is best when I find them. Laser Reaserch Optics (http://laserresearch.net/) are good; 80% OC is $90 and a 10m Si reflector is $70. Shipping to UK is $25.
Click here to see a bit about my first laser in the Dec. 2003 departmental newsletter from the Physics Dept., University of Strathclyde (http://phys.strath.ac.uk). Thanks to Klaas Wynne (http://www.wijnne.com) for putting it in!
14/12/10: An update, years later....I have since bought a CO2 laser cutter with a 40W tube in it, so I'm not intending to try making any CO2 lasers in the near future!