Poor-Man's Co2 Laser

Modern Co2 lasers, including mine, use ZnSe for output coupler optics. This material is used to both reflect and transmit the 10.6 micron wavelength. At the expense of performance, I constructed a ZnSe-free laser using nothing more than a first-surfaced mirror with a small opening through which to pass the output beam, and a salt window to seal the tube. Rock salt is one of the very few materials (probably the least expensive) that will actually transmit the 10.6 micron wavelength. Most materials that are clear in visible light, such as glass and clear plastic, are totally 'black' to the Co2 laser wavelength.

If you were building a Co2 laser on a budget (I'm on a strick budget, but my ZnSe optics were donated to me), without access to modern supplies, the hole/salt window approach would likely be the easiest route.

For a time, I struggled with the problem of aligning the OC. Then I did something very simple: after aligning the HR, I placed a standard first-surfaced mirror (without a hole) over the outer O-ring seal, and aligned it by reflecting the HeNe beam off of it's surface (using atmospheric pressure to hold this mirror firmly in place during alignment). Such a glass mirror can be generally regarded as being flat, and the interior surface can therefore be considered parallel with the exterior. After alignment was complete, I removed this mirror and replaced it with the OC and salt window. Such a procedure appears to be good enough, considering the simplicity involved.

It is necessary to run the vacuum pump during alignment, even if atmospheric pressure is not required to secure the optics. If the optics were aligned without reducing the pressure within the tube interior, the alignment would change after the vacuum pump was activated.

Category:

Science & Technology

Tags:

• Salt
• Window
• Laser

[chilidress]

a laser full of pure co2 will work? nicely?

[magx1]

@chilidress

In theory - no. In practice, some lasing can be obtained with CO2 and air (nitrogen). Optimal performance is obtained using 10% CO2, 20% N2, and 70% He. There's a big difference between this and a commercial laser, in terms of performance for it's size. For me personally, homemade lasers are more interesting than commercial ones. To each his own. I've seen some truly amazing work with commerical tubes/lasers. Some folks, more than I, are inclined towards theory and electronics.

[rbneville]

Man you saved me alot of worry. i had been thinking about using a mirror with a hole in it instead of Zinc mirrors, but i wasnt sure if it would work

[magx1]

@rbneville You can get away with a lot if you just want a working laser. In fact, it's really more fun when you do it as much as possible from scratch. It's obviously easier (if not altogether necessary) to get good performance with a proper ZnSe output coupler.

With my examples, the beam spreads more than with ZnSe. It's passing through a hole and non-polished salt window, so this isn't surprising.

[rbneville]

@magx1 I am saving up for a small vacuum vapor deposition system and i was thinking about masking off a dot in the center before coating the mirror with Al then after coating just remove the masking. Do you think that would work?

[magx1]

@rbneville You must have a hole in the glass. The CO2 laser wavelength will not pass through glass. This is the purpose of using the rock salt window over the hole: rock salt is the only common substance I know of that is transparent to 10.6 microns.

[Lachieh923]

@magx1 cool, and is that just regular aluminium first surfaced mirror? also, i am currently designing a co2 laser, and i like to build things from scratch cos its cheep and more fun. so instead of a glass neon or xenon tube (i want the glass so i can see the cool purple colour :P and i cant find any neon tubes) do you think i could use clear glass beer bottles, cut open and either expoxied or, if i can get a blow torch, braised together to make my laser tube? or will it be too fat?

[dtiydr]

You say rocksalt, would ordinary table salt work as well or this is the same? How do you make the salt window?

[169Phoenix]

Put your hand infront of it and let us see!! lol

[sil0o]

looks like a giant ear plug for james bond.. new gadget maybe?