Diode help?

[ElektroFreak]

Simon was gona help me sort lens out for these diodes but due to his new arrival i think its only fair i leave him alone

so the diodes are 1watt 635nm in 9mm cans

ive been told i need a cyllinder lens to correc tth beams.

can anyone help me out here?

The minimum requirements for collimating multimode diodes like that are a cylinder lens for the fast axis and a convex lens for final collimation. Experimenting with various configurations should yield a nice relatively low-divergence square beam.

This paper contains even more advanced and better methods for obtaining a good beam from a diode laser, and mentions using cylinder lenses at the end. It is actually intended for use with single-mode diodes, but the principles work with multimode also. The first figure in section 3.2 shows the uncorrected raw output of a laser diode. The fast axis is the wider of the two axes in the elliptical beam profile.

Hope this helps.

[smogthemog]

I have two 500mW versions of those in my 1W 635 both with FAC lenses.
It's true you get a square beam but they are tiny compared with say the CNI type multimode modules.
Are you going to be PBS'ing them together Andy?

[ElektroFreak]

^It's been my understanding that the reason that CNIs beam diameters are so large with their multimode reds is that they basically have a beam expander inside the head to help improve divergence. Multimode diodes generally have fairly bad divergence even with the basic collimation optics.

[andy_con]

Andy
i would have left the jumper on until fitted in its housing as while its a loose diode that Lasorb though protecting the diode is more likely to get knocked off!

Rob

... also; you need to be able to slide a tubular tool over the pins to press the diode home.

that setup was just for testing that the diode worked and which way round to solder the lasorb on. it has since been taken off and the jumper put back on

The minimum requirements for collimating multimode diodes like that are a cylinder lens for the fast axis and a convex lens for final collimation. Experimenting with various configurations should yield a nice relatively low-divergence square beam.

This paper contains even more advanced and better methods for obtaining a good beam from a diode laser, and mentions using cylinder lenses at the end. It is actually intended for use with single-mode diodes, but the principles work with multimode also. The first figure in section 3.2 shows the uncorrected raw output of a laser diode. The fast axis is the wider of the two axes in the elliptical beam profile.

Hope this helps.

thanks for this i will take a read.

where would one look to buy the require lens?

I have two 500mW versions of those in my 1W 635 both with FAC lenses.
It's true you get a square beam but they are tiny compared with say the CNI type multimode modules.
Are you going to be PBS'ing them together Andy?

yes i saw simons red setup when it was half built, thats why i wanted his help. but quite rightly lasers arent on the top of his to do list at the moment.

and yes i will be using a cube to combine two of them. im looking at running two at 800mw each.

[ElektroFreak]

^Chris might have some good lenses, also definitely check out www.surplusshed.com..

[andy_con]

thanks but think im gona need to wait for simon as im really not sure what im looking for.

got bored today so did a little diode testing.

put the lasorb back on, set the tec up and run the diode on full power for about 30 seconds.

geee 1watt of 635nm is bright cant wait to get them properly setup.

[andy_con]

LOL

as normal with me there will be plenty of pics dont worry.

ive got everything needed just missing the lens at the moment.

[ElektroFreak]

^usually the beam specs will not be good enough to use in a scanner (too much divergence, narrow rectangular beam cross-section) if you only use one convex lens (or all convex lens assembly) with a multimode diode. In order to use those diodes successfully they most likely need multiple types of lenses. I don't know if those diodes come with FAC or not. If they do, then those meredith modules will work fine. Andy, if you get a chance could you post a picture of the diodes raw output projected onto a white card from about 5-10cm away. Then we'll be able to see if they have FAC lenses or not.

[andy_con]

your wish is my command, with flash on and off

[ElektroFreak]

No FAC lens there.. If there was, the output would be a much thinner rectangular line compared to what we see there.. Also, the fast axis will be perpendicular to the plane of the pins. If the pins are vertical (very close in the pic), the fast axis will be horizontal. Based on that you can tell that the fast axis has not been collimated at all.

Just for reference I'm posting a picture of a cmount diode with FAC lens so you can see just what a FAC lens looks like. It is a piece of single-mode fiber placed across the diode facets. The cylindrical shape of the fiber makes it act like a cylinder lens. Occasionally I've heard of 9mm diodes having integrated FAC, but the VAST majority of the time they do not.



EDIT: I forgot to add that Chris sells multimode diode collimating lens assemblies that are specifically for this purpose. I have one myself, but I haven't tried it out yet, so I don't know firsthand whether or not it would be good enough for a low-divergence beam.. worth a try, perhaps.