[dar303]

Hi,

I have 16W Synrad 10,6um that has a 4mm output beam diameter. My focus lens is 12,5mm and I would like to have a bigger beam to optimize focus spot without resorting to placing mirrors to get a longer beam-path.
Do anybody have an expander to sell me?

/Daniel

[zax15uk]

Daniel,

I do not understand, what are you trying to do?

Why would you need a larger spot size - it will have no power density?

Zax.

[bdring]

In some applications a beam expander before the lens is used to optimize spot size and focal length.

There is a good write-up on the subject here.
http://www.parallax-tech.com/faq.htm

also see the laser optics calculators here.
http://www.buildlog.net/cnc_laser/laser_calcs.htm

[dar303]

Good links, thank you!
I want a larger beamsize before the collimating lens so I can have the optics closer to the laser, ie no flying optics.

[zax15uk]

I understand the use of a beam expander before the lens to extend focal length and working distance.

What I question is using a beam expander on a 16W CO2 system to allow the optics to be closer to the laser.

Zax.

[dar303]

I want to mount the laser directly to the gantry and not have it outside the machine using mirrors etc.
It works ok now (with no beam expander, just focus lens and air assist nozzle) but minimum spot size is a bit to big for my taste though.
This is a hobby project and I like to experiment and learn!
Why is the expander a bad idea in your opinion?

[zax15uk]

A beam expander usually consists of 2 lenses, depending on quality the transmission loss for the pair will be ~85-90% for standard quality ZnSe.

High quality module could be better, perhaps >95% but at considerable cost.

I encourage you to experiment, and post the results.

Zax.

[DaveDoesIT]

I have 16W Synrad 10,6um that has a 4mm output beam diameter. My focus lens is 12,5mm and I would like to have a bigger beam to optimize focus spot

A Collimator lens may help a little but with 16W you are not going to gain much.

Dave