Gas laser principle

[nanovrej]

Hi, it's the first time I'm posting.
I bought a HeNe Spectra-physics 105-1 10mW laser recently as a collectors item. I guess your could say I'm a amateur chemist/physicist.

1. I got the impression that a lasing tube needs to have a specific length. In other words, if you have a 632.8nm light then the tube length needs to be some multiple of this length so that you would have a standing wave in the tube.

2. What about the mirrors. How are they constructed? Is the mirror welded to the lasing tube or is it outside of it? What material is it made of?

3. I have seen in a book, one of these laser lights going through a test tube filled with neon (ordinary pressure?). The neon glows brightly red where the light goes through it. You don't need a fog machine! Anyone tried this?

 

[daguin]

Hi, it's the first time I'm posting.
I bought a HeNe Spectra-physics 105-1 10mW laser recently as a collectors item. I guess your could say I'm a amateur chemist/physicist.

1. I got the impression that a lasing tube needs to have a specific length. In other words, if you have a 632.8nm light then the tube length needs to be some multiple of this length so that you would have a standing wave in the tube.

2. What about the mirrors. How are they constructed? Is the mirror welded to the lasing tube or is it outside of it? What material is it made of?

3. I have seen in a book, one of these laser lights going through a test tube filled with neon (ordinary pressure?). The neon glows brightly red where the light goes through it. You don't need a fog machine! Anyone tried this?

Welcome.

However, most of this info is easily and quickly available to you from a simple Google search. Why would you want somebody here to sit and re-type stuff for you that is so easily available online?

In addition, while you are reading the webpages you find, you will be learning much more than just the answer to these questions

Peace,
dave

 

[ElektroFreak]

A great source of gas laser info is Sam's Laser FAQ, a link to which is in my signature below..

 

[nanovrej]

Thanks, I'm still reading that Sam's FAQ. It is an impressive site.

 

[daguin]

Thanks, I'm still reading that Sam's FAQ. It is an impressive site.

LOL! We'll see you in couple of weeks then

Peace,
dave

 

[LSRFAQ]

If you have a decent library around, Silfvast's book is a better read for what you want to know, and he invented the helium-cadmium laser, as well as some others, so the book leans toward a bit more applied then theoretical.

Title is Laser Fundamentals, William T. Silfvast 2004.

He does not just do the usual math, but covers designing the cavity etc, all in very readable terms, and without that much calculus, mostly simple algebra. It starts out at basic and works its way up to Grad Student in every chapter, so you can stop at the level of explanation you need. Again, it comes from a guy who started a company and built lasers besides being a Professor.

Get the first edition, it has a much better cover photograph!

And the answer to your question is that light usually can find the required (N) * c* lambda/ 2 * cavity length spacing in just about any cavity at least a few hundreds of wavelengths long. Some lasers with very long wavelengths, like Co2 lasers, can be a bit fussy about cavity length, but visible lasers usually are not, provided the amplifier section has enough gain to cover the internal optics losses.

Steve

Laser fundamentals - Google Books