He-Ne gas lasers
A helium-neon laser was the very first working gas laser, it was made for the first time in 1960 in Bell Labs. This laser is made of a glass tube filled with gas at low pressure, the tube is ended with mirrors which forms an optical resonator. There are two metal electrodes placed inside the glass tube to provide high voltage for gas ionisation.
It can be quite suprising that in the He-Ne laser gas is a mixture of helium and neon :P This laser generates 632.8nm EM wave (red), but it can be forced to generate other wavelengths (e.g. 543.5nm - green) by using mirrors with special reflecting coating that reflects only required wavelength. He-Ne lasers are applicable in holography, medicine, spectroscopy. Before laser diodes became available the He-Ne lasers was the most popular lasers, it was used also in barcode readers, photocells, and as it turned out ... at discos.
The laser tube described here comes from an old disco laser. Below some photos of this lasers construction.
Date of manufacture is unknown, a company who made it probably collapsed a few years ago. I've bought this laser cheap as not-working with hope that I'll find galvos inside. But after I had recived the package it turned out that there was only two DC motors with mirrors ... Fortunately there was also a big laser tube (I didn't expected that there will be a gas laser) so there was this little benefit of buying it, becouse I had something to play with at least :) Photos below shows how this laser tube looks and how it works.
As a HV supply a C-W multiplier is used. It is powered directly from 230VAC and it gives 9mA@2kV DC to the laser electrodes. This laser emmits probably a few mW of power.
Below a few more photos, on the first one light spot at about 6m distance. It has about 3cm diameter, when at the end of laser tube diameter of the light beam is ~1mm.
Below a few pics of the second He-Ne laser I had some time ago. It was manufactured by Melles Griot, it's output power is about 1mW. I used a tiny power supply that needs only 5V to operate. It's a dedicated he-ne laser power supply, but from other laser than the one on the pictures (I bought it separately).
Something new again :) The next He-Ne laser I got comes from some disco equipment just like the first one described on this page. But, what I found out after buying this laser, it's yellow! :D Yellow He-Ne lasers emmits 594nm wave, they are rare in comparison to regular 633nm red He-Nes, so I'm really happy I have this one :D Also one more thing is interesting, both mirrors of the laser cavity are output couplers, so it emmits two beams from each end.
Below some pictures of this laser.
And here another one :) This is red 633nm He-Ne laser. It's been made in Poland and the construction is really massive, with huge PSU - it's probably very old. According to my laser power meter I bought on ebay recently, the power of this laser is 0.3mW. Below you can see some pictures.
I bought two sets like this (laser + PSU) and one of them was broken. It turned out that the laser itself was broken, not the PSU. I took apart the broken laser, you can see it on the pictures below. On the third picture you can see some tarnish inside the tube, probably the tube is cracked somewhere and not tight anymore - that's why it doesn't work and that's why the tarnish appeared.
On the last pics you can see the power supply and what it has inside.