# A Laser beam folding

1. Mar 29, 2016

### rppearso

Why is it that equivalent length is so important for laser beam power output (Length = Power/60) - http://www.laserk.com/newsletters/whiteCO.html. I was reading that in order to get multiple kilowatts of power out of a CO2 laser beam you have to fold the beam a great number of times. Why is this the case? Can you instead make the rear reflector a concave mirror and then put a focusing lense in the apex of the concave mirror in order to boost the beam strength?

I am trying to build a 10kw CO2 laser and want to make sure I am taking everything into account and that I understand why I am doing what I am doing.

In order to get 10kw of power based on the equation above the total equivalent length would be 166 meters and I have a 1 meter long glass tube about 3" in diameter. I suppose I could try to design a single piece multi reflector inside the cavity but 166 times bouncing around would be tough. Is this how they are making 10kw lasers for DOD, etc?

I have gone through the following books -
Svelto O. Principles of Lasers (5ed., Springer, 2009)(ISBN 1441913017)
Milonni P.W., Eberly J.H. Laser Physics (Wiley, 2010)(ISBN 9780470387719)
I am looking for a copy of the following to review soon -
Lasers - Anthony E. Siegman

It seems these texts like to cover a bunch of material but kind of dance around the details required to actually build a high power laser (minimum of 10kw IR beam power).

2. Mar 29, 2016

### Staff: Mentor

I'm not an experimentalist, so I may be wrong, but the point is not concentrating the light, it's having more lasing medium.

3. Mar 29, 2016

### rppearso

So folding the beam is not so much the issue as is having more pressure (more gas molecules) inside the tube? As well as more voltage?

Do you know if there are any laser societies so that I can seek out a mentor for very very detailed work on laser cavity design so that I can achieve a 10kw laser.

Last edited: Mar 29, 2016
4. Mar 30, 2016

### f95toli

It would -fortunately- be impossible for an amateur to build a 10 kW laser, so the answer is most definitely no.
I suspect part of the problem here is that you might not realize just how powerful such a laser is. We have plenty of lasers where I work but any work that requires a class IV laser can only be used in special labs that can only be accessed by trained users, and only then using special safety equipment (interlocks, goggles etc) .
Class IV is the highest classification of lasers and encompasses any laser with an output power or more than 500 mW. This is already enough to burn your skin and even a reflected beam will make you go blind. You are talking about a laser that would be 20 000 more powerful than this
Note that CO2 lasers used to cut sheets of steel usually have an output power of around 200W or so and 3-4 kW CO2 lasers can cut 1/4" sheets of steel at a fast rate. There are very few applications that would require a 10 kW continuous laser (mostly research)

5. Mar 30, 2016

### Staff: Mentor

I thought you were doing a PhD in the field or something like that.

What you are trying to achieve is too dangerous for us to help you out.