Lazy Mans Beam Expander for 445nm NUBM44 6+ watt laser diode.

[Alaskan]

I use it to play with some of my smaller laser hosts, I have about 12 beam expanders of different types, I just like to collect them, occasionally use them.

 

[Trendkilla254]

I must spread some reputation around. Sorry bro.

 

[Alaskan]

Thanks, I always rep you when I can.

Instead of buying a 79 dollar helical focuser and finding a lens to make it work, some of the camera telephoto lenses (the whole assembly, not just the lens alone) on ebay will work with a little adjustment and can often be found for 20-25 dollars. Here's a thread about one I converted into a beam expander using the same principle as the one in this thread:

http://laserpointerforums.com/f49/m...photo-lens-converted-beam-expander-95082.html

 

[Alaskan]

Been awhile since I've posted in this thread, here's another beam expander made from the same helical focuser and a large 5 inch diameter lens. Here's a link to the funnel shaped piece of aluminum I used (you can order aluminum or stainless, I opted for aluminum):

2" 4" 304 Stainless Tubing Transition or 2 3 2 5 3 5 3 4 Exhaust Race | eBay

The output from my NDG7475T 520nm diode does not have a G2 or any other kind of lens inside, just the raw output into a huge lens. The beam itself is just over 4 inches diameter out of the lens which is a rectangle shape. Edit: I found I had to put the G2 lens back in and defocus it to the right width in order not to have a portion of the beam cut off, the length of the neck was a little too long and was cutting off too much of the power, so I put the G2 back in.

Why do this? I bow to low divergence!

 

[RedCowboy]

Nice! Cant rep you yet but I like this.

 

[Alaskan]

Thanks, it put a nice bright green spot on a 6,000 foot high cloud base tonight Only thing is, those darn wings! I can't seem to get rid of them unless I mask the beam output using this kind of beam expander.

 

[Alaskan]

Humm.... well, I haven't seen the wings before I started using these high power multimode diodes, didn't know that. I would like to go to that link, but it isn't working for me.

 

[Laser Chick]

Just so you know. I just clicked on the link and it worked okay. I am using a laptop.
You have some very interesting beam expanders.

 

[Alaskan]

OK, link is working. I don't really understand much about the diodes themselves, well, for that matter, I don't know much about optics either but I do experiment with different configurations and from that, learning by the seat of my pants.

Thanks for the link, read through some of the sections which I found very interesting. There is a lot on that page to read!

Edit: in regard to the Astigmatism, maybe that's it, I did try to see if I could focus those wings in or out, more or less, and couldn't get rid of more than half of their width through varying the focus, at least, not with the 1.5 inch range of focus I have with this zoom focuser but perhaps if the range of focus were greater it wouldn't help anyway. I've noticed with some lenses, I can finely focus one polarity or the other (uncorrected rectangle output), or in other words, focus the fast or slow axis to a finer spot in the distance, but this big lens isn't acting that way. The wings will go completely away if I take the focus out of infinity to make a very large diameter output all the way out for as far as I can see, but then it doesn't make a bright spot on a cloud base, of course, expanding a little too much to do that. When I do that, I don't think it is really making a large diameter all the way out as far as I can see, but perspective makes it look that way as if it were a non-diverging beam when in fact, it is diverging at a much greater rate.

 

[Alaskan]

I can't get rid of these wings with my NDG7475T diode very easily either, it seems the larger the diameter the lens, the more I have wings at certain focal settings. I'd like to get a firm handle on what is going on with this, not sure it is astigmatism or not yet, how to know for sure?

I have a eight inch diameter PCX lens coming in the mail soon, planning on using an old aluminum conical sieve to mount it into, unable to find anything better for mounting big lenses in for a pointer yet. Ehgemus found using some plumbing transitions can work, but I don't like how they look, I'd like more of a cone like these:

http://www.ebay.com/itm/131617599846

I'm thinking if I cut the tip off I can insert a pointer and put a lens at the large rim, removing the handle, of course. Similar units can be found up to 8.25 inches OD, this one is probably closer to 6 inches but you could fit much smaller lenses into it, they would just go deeper inside, cutting off the excess, if you see the need. A wide cone like this is needed for the raw output of a laser diode due to their rapid expansion without a lens in front.

 

[Alaskan]

Cool video, my lasers do the same thing at the end of the beam but I also have these wings off the side of the end of the beam, even when focused as tight as I can get it, like in this photo:

http://i853.photobucket.com/albums/ab95/LaserProject/239d51ca-3804-4d40-a78b-f195ef0b414b.jpg

Those are some nice lenses for cheap at that electronic goldmind, I will have to order that optical head

 

[Alaskan]

I have some RGB cubes like that I would like to combine some diodes together with someday to make white, as soon as I get my knife edge project completed Ehgemus is working on for me right now, I hope. He might be on hiatus, haven't seen him on the forum for awhile.

I did order some of those lens and mirror box assemblies from projectors, shipping nearly doubles the price all together though, but still a great deal anyway. I have some large lenses which are somewhat concave on one side, maybe they will help with the fanning or wings I am seeing with my NUBM44 output towards the end of the beam, otherwise I have to use an iris to mask them out but that is just throwing away power.

 

[Alaskan]

I need those 6X cylinder pairs too, hope we can get that GB done.

Yea, I saw that ebay listing a month ago when the price was much higher, I offered 50 on it then but they turned me down, now I am not interested in it, appears to have a low magnification factor. I have the wings worked out on my NDG7475T 1.5 watt green 520nm laser diode and host using a 3 inch diameter PCX lens on a 2 inch diameter output aperture, so some of the lens is hanging over the sides of the tube where I have it glued to the end of it. That lens doesn't produce wings when I put a small PCX cylinder lens inside right next to the output of a expanded/de-focused G2 lens:

This is a Ehgemus host with a sliding tube in the end to adjust focus. 2X 26650 batteries.

I did find and buy this yesterday for 125 USD: http://www.ebay.com/itm/161847797943 - A 25X expander, but the input beam must have to be very small at close to 1.2mm if the output aperture is only 30mm, according to page 93 of this doc: http://www.winlens.de/fileadmin/user_upload/Dateien/Catalog_EN_07_08/03-Optical_Systems.pdf If so, this expander is probably well suited to the RPL-260 Dr Evil had for sale with its thin <1.5mm beam diameter.

 

[kathsa2000]

Thanks, it put a nice bright green spot on a 6,000 foot high cloud base tonight Only thing is, those darn wings! I can't seem to get rid of them unless I mask the beam output using this kind of beam expander.

6000 ft? Wow. Nice! Just happened to see this and was thinking of doing something very similar! Used to do this with a 1.8W near IR diode laser.