Optima lens for reds

[The_Doctor]

Just to be totally perverse and risk extending abject confusion to hell and back, what did happen when someone tried a 405-G-2 lens on a G71 or P73? I bet someone did. Was it ridiculous, or did it look like it was worth doing, at least in absence of more suitable lenses? If anyone got any specs for aperture width, divergence, and relative power loss, please post. I read enough to to know this thread wasn't actually mixing the lenses and diodes this way, but the ambiguity is interesting, and if anyone did go that far, what resulted?

EDIT:
Apparently dnar did it:
http://www.photonlexicon.com/forums/...191#post226191
Looks like it worked too, see the post three posts above that one. Any more word on this notion?

[andyf97]

Any lens with no coatings would by definition work on a G71 or P73.

One which would create a nice beam has two answers depending on the target application.

Single or dual combined beams means one type of lens; 3 or more stacked beams means another lens.

If you want to learn about it then the best is to read the Holy Grail thread which covered this subject in huge detail by many international laserists.

http://www.photonlexicon.com/forums/...lashlight-Fail





< 3mm FL is where you should be looking in all cases.

[andy_con]

I gather by recent posts your interested in reds doctor?!

At the end of the day if your interested in beam quality single mode is the only way

[The_Doctor]

Well, that;s what I always thought. I have never used any other kind. So when I see Planters and others saying that combining several SM diodes makes things harder and more expensive than using a few narrow-emitter multimode diodes, I think it's worth a bit an explore.. I'll never ignore single mode. THing is, I need to deal with something I did ignore. In the years since I left, people have done things beyond anythign even experts were previously claiming for multimode diodes, so I might as well check it out a bit.

Andy (the other one) I saved that this morning (all 55 pages of it) because PL went down a few times recently. I decided that if I'm going to hit it hard I might as well grab it for local archive so it only hits the server once. I think I hit that pretty hard too, my first attempt to get that thread. Note to anyone interested: don't automate download of a forum thread recursively to get all its pages! Great for web sites, not so hot for cross-linked threads... Horrible mistake, and I made it, and stopped the program before it got out of hand like the Sorceror's Apprentice's efforts with a broom. Can only warn others against... Do it manually for the thread wanted.

About the lenses, I know that a lens will work with any diode, but the poinjt IS the coating. I thought the 405-G-2 WAS specifically coated for blue, actually (I presumed) 405 nm originally! I have a datasheet but it shows diagrams, says nothing about the coating beyond 'multilayer "A"' which is about as uselessly cryptic as it gets... So the question still stands: did those who used 405-G-2 with its standard blue AR coating get respectable results for efficiency with shortwave red? I wouldn't have expected it, but apparently at least one person did it and liked it.

[planters]

So when I see Planters and others saying that combining several SM diodes makes things harder and more expensive than using a few narrow-emitter multimode diodes, I think it's worth a bit an explore.

The power ratios are pretty high. SM @ 170mw vs MM @1W means knifing six SM diodes vs beam correction for the one MM or twelve vs two etc. I am not advocating either one, but I have a lot of experience with both knifing and correction and the effort might be comparable. What I have yet to see is the two beams side by side. Six SM vs one MM; what do the near field and far field beams MEASURE out at?

[andy_con]

Don't forget the 110mw single mode 638 Diode a fraction of the price.

Even when combining lots of single mode diodes the beam quality is far cleaner than multi mode

[The_Doctor]

Well, by the time I'm done messing with the G71's I imagine the Opnext 170mW will also have come down in price.

Basically I'm after something substantially different from my experience with earlier Opnext diodes and Rohm diodes. Only that new Opnext (Oclara?) makes the jump, and right now the cost is better spent on learning something new firsthand. I will go back to it though. Single mode guarantees a much easier life, and I'm all for it, but I got convinced to look at something I previously refused to try, which is a healthy state to be in, so I'll ride it for a while.

There's another reason I'm doing this... which might help explain some erratic decision making a few people may have noticed in me since I came back.. I love TEM00 beams, clean, sharp, low divergence. no astigmatism or asymmetry. Even single mode diodes fall way short of this, perhaps even after spatial filtering. Just having electrodes attached to tiny semiconductors does for the clean homogenous precision of gas or crystal. So if it's going to get messy, I might as well see if I can use some really messy diodes and find them to be a lot more fun than I thought they'd be. Judging by the effort put in by so many people, I'd say it's a good bet I will. If I go into this without high expectation, I'm unlikely to get disappointed the way I was with those Rohm's.....

[andy_con]

think about it like this

1x 500mw 638nm diode = 3.5mm by 2mm beam at aperture and around 1.2-1.5mR and its a messy beam and needs correction optics

4x 170mw 637nm diodes = 680mw = 2mm by 3mm at aperture @ 0.6mR no corrections optics and a perfectly round beam.

but there is a price difference between the two

[steve-o]

Just to get ya back up to speed Doc, the lens of choice is the 2mm fl which Dave sells at his store, combined with a cylindrical lens pair which was a group-buy and I think Dr Lava sells cyls too. These work very well for the high power multimode P73 and G71 638nm red mitsu diodes, and some people are getting 1+ watt per diode from these with adequate TEC cooling . Not ion quality beams of course but the divergence has been tamed and imho the beams are of good quality.

[The_Doctor]

think about it like this

1x 500mw 638nm diode = 3.5mm by 2mm beam at aperture and around 1.2-1.5mR and its a messy beam and needs correction optics

4x 170mw 637nm diodes = 680mw = 2mm by 3mm at aperture @ 0.6mR no corrections optics and a perfectly round beam.

but there is a price difference between the two

And a halfway point? Two G71's seems like a plan for me... And if it works I can scale that up later to four. Whatever I get, hopefully it will be worth selling a few to get money for better plans later.