D-lensing a Donut

[LesioQ]

Hi,

At some time ago I got a few 5-bar pump donuts from You-know-where.

http://www.ldai.com/photo_pages/a_pages/act_1.htm

My calculations resulted that unless I plan to use a 7mm dia rod, I will have to correct the fast axis divergence.

First idea was to use :

http://www.doriclenses.com/produits/122.html

... but pricing for 25pcs. was not easy for me

I decided to make my own d-lenses. I used a 1000um fiber, ground a half of it's thickness and polished a bunch of long cyllinder lenses, then cut them into 10.5mm long pieces.

My plan was to glue each to a bigger AR/AR substrate, 0.15mm thick. These are readily available You-know-where as overstock windows from Lightwave pump modules.

For glueing I chose long-UV cured NOA-61 by Norland (from Edmund). This adhesive has good transmission around 800nm, so I hope it will survive 25W of 808nm transmitted. I hope it will also help reduce reflection from AR substrate to uncoated d-lens transition (by refractive index matching - no air between).

Now I have about 30 d-lenses on bigger substrates, each about 6 x 10mm.

My plan is to position them on each donut laser bar, then fix in position using same NOA-61. And here comes my doubt

I don't want to run LDs up to lasing threshold; I'd prefer to use it's low current noncoherent emission for precise positioning of cyllinder lens.
Precision's required because I want to pump 3 or 4mm dia Nd:YAG rod, so have to keep LD pump light at donut center.

Do You think centering the LED emission of LD will assure centered laser emission, when LD current goes up ?

Piotr.K


Here go some pics:

[krazer]

To answer your question, yes you can focus the LED emission and go from there. For all intensive purposes, 808nm bars are just high intensity incoherent sources, and aside from the tight(er) linewidth/higher power the laser and led modes aren't really that different.


But to give you some help on your problem... I have the donut modules out of a coherent Avia, which are the 5x diode bars and a 3mm yag rod. The only optic between the bars and the rod is a flowtube, which is a very thick piece of quartz that is coated HR@808nm on most of the outer surface, with 5 small 'slots' that are coated AR@808nm that are aligned with the diodes.

For some pictures of the beast (and a solidworks model if you are into such things) check out my website http://www.krazerlasers.com/lasers/avia/

[LesioQ]

This solution sounds attractive, a bit similiar to CEO (Northtrop) pump cavities now cloned by China Sinolaser, however without access to exact parts will be hard to complete.
Two pictures from Your site are unaccessible:

http://www.krazerlasers.com/lasers/a...20overall3.jpg
http://www.krazerlasers.com/lasers/a...le/5%20end.jpg

I wish I could see them as well

I'm planning to use simple Simax flow tube without any AR/HR coatings, so will have to hit the rod in the first pass

Piotr.K

[krazer]

This solution sounds attractive, a bit similiar to CEO
Two pictures from Your site are unaccessible:

http://www.krazerlasers.com/lasers/a...20overall3.jpg
http://www.krazerlasers.com/lasers/a...le/5%20end.jpg

I wish I could see them as well
Piotr.K

fixed

I bet if you ask nicely sinolaser would be willing to part with a flowtube and an end cap or two, they look pretty flexible.

But since you have already got your stash of d-lenses made up, its certainly worth a try to get them working! If anything, you might want to make a few extras, I believe that FAC's for diode bars are in fairly high demand in these parts (I could certainly use a few)