Fiber collimator

Hi all,

I have a 25W IR laser, the output of which is from a fiber (around 8 inches of fiber). I'd like to collimate the output of this fiber, to achieve a reasonably small (under 2mm) parallel beam.

I've tried to do this using a single focussing lens, but to no avail - I just can't achieve a parallel beam.

Why isn't this approach working, any ideas on how to make a collimator, or sources for a commercial collimator please?

Grunff said:

Hi all,

I have a 25W IR laser, the output of which is from a fiber (around 8 inches of fiber). I'd like to collimate the output of this fiber, to achieve a reasonably small (under 2mm) parallel beam.

I've tried to do this using a single focussing lens, but to no avail - I just can't achieve a parallel beam.

Why isn't this approach working, any ideas on how to make a collimator, or sources for a commercial collimator please?

Click to expand...

25W or 25 mW and I am pretty sure you cant collimate after the beam has gone through the fiber optics.

KiLLrB said:

25W or 25 mW and I am pretty sure you cant collimate after the beam has gone through the fiber optics.

Click to expand...

I'm quite sure fiber coupled diodes are mostly in the 25W region. It's collimated through the fiber optic so you can have precise control of where you are burning, and it can be run through a X/Y cutting machine without size issues in the head.

KiLLrB said:

25W or 25 mW and I am pretty sure you cant collimate after the beam has gone through the fiber optics.

Click to expand...

It's 25W, really :yh:

I've found a few commercial collimators, but can't find where to buy one. Like:

Thorlabs.com - Fiber Coupled Collimators

Also, since this is a hobby project, I'd prefer to build one if possible.

Grunff said:

It's 25W, really :yh:

I've found a few commercial collimators, but can't find where to buy one. Like:

Thorlabs.com - Fiber Coupled Collimators

Also, since this is a hobby project, I'd prefer to build one if possible.

Click to expand...

Hmm I was unaware you could collimate laser light after it passed through several fibers effectively changing the path of the light through each fiber.

Grunff said:

It's 25W, really :yh:

I've found a few commercial collimators, but can't find where to buy one. Like:

Thorlabs.com - Fiber Coupled Collimators

Also, since this is a hobby project, I'd prefer to build one if possible.

Click to expand...

maybe something like... LASER SYSTEM OPTICAL COMPONENTS [ International Laser Productions ] ?
3 Down.

I don't know if it can handle 25W tho, but may be cheaper than thorlabs.

You can collimate the output from the fiber. You have to take into account several factors including the size of the fiber, the numerical aperture of the fiber, and the desired divergence of the fiber.

Because you have a 25W diode, I am assuming you have a Coherent FAP or similar diode, which means you have a fiber with 800um diameter and 0.2NA. That means you will have a 800um 25degree beam directly out of the fiber.

Now, you can figure out approximately what size you need to have to get it to the divergence you want. Multiply the beam diameter by 2 for each time you half the divergence. For example, if you wanted to have a 12 degree beam, you would now have a 1.6mm diameter beam. Do that again and you are down to 6 degrees with a 3.2mm beam diameter.

As you can see, you will have a very large beam before you get a low divergence.

I also have these focus tools which are NOT designed for colimating only focusing

The worse problem, with fiber coupled units, is that, usually, there's not a single fiber, but a lot of them, paralleled, so it's almost impossible to obtain a single "beam" from a collimator (maybe with a 2-elements, or a 3-elements, collimators, but this become a lot high cost, usually)

They are planned, mainly, for transfer the IR to a "point" collimator for burning/etching/cutting purposes, not for make "straight beams"