445 divergence?

Still in the testing mode of my new 9mm 445 build. I'm new to multimode, and wonder if there is divergence variation with this diode like there is with output? I'm getting a 8" in focus line at about 75' to 80'. This with a G2 lens. Does this sound about right?

That works out to over 8mRad which seems pretty high. I think 3-5mRad is more typical, but it's been a while since I've played with them. Your beam might not be in focus.

Cyparagon said:

That works out to over 8mRad which seems pretty high. I think 3-5mRad is more typical, but it's been a while since I've played with them. Your beam might not be in focus.

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I was afraid of that. It is in focus. Anyone have a guess as to why? variation in diodes? Some issue I can fix?

old gen or new? the new ones are much more powerful, but have worse divergence

This is supposed to be the older 9mm with beter divergence, but I was thinking that maybe I got the new one? I'm getting 2800 mw at 2.2a. I'll neeed to do an offical measure tomorrow, but when aiming at my shed with t-11 siding the line will span 2 (slots) wich is 8", this at what I beleive to be near 80'.

Anyone want to recommend good distances to measure to determine whats going on?

If it was the new gen it'd be doing about 3200mW @2.2A, and would have cost you $300.

I remember my old gen 9mm being pretty bad with a g lens though, beating only a multimode 638nm divergence wise.

consider a beam expander. they do wonders for ugly beams

I am interested in beam expanders, but rather not start off behind the curve.

Anyone have a guess? Would the culpert be the G2 lens, or the diode? How do I determine?

Try the 9mm Lens and check the diodes distance from it...
-Shane

Are you absolutely sure you're got the tightest focus?

The lens barrel might not be fully screwed into the focus adapter, causing the focus adapter to tighten before the laser has achieved tightest focus.

ryansoh3 said:

Are you absolutely sure you're got the tightest focus?

The lens barrel might not be fully screwed into the focus adapter, causing the focus adapter to tighten before the laser has achieved tightest focus.

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Yeah the focus is good. I have plenty of adjustment on both sides of focus.

HitShane said:

Try the 9mm Lens and check the diodes distance from it...
-Shane

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I have the day off tomorrow, and will do some better measurement with rulers, and tape measures. I will also try my G9 lens.

1. Can anyone tell me the expected line length at 50', and @ 75' to help with my testing? Again, with the "standard" 9mm diode, and a G2 lens.

2. How common is larger than expected divergence? I really see no other reference to this issue. I can't be the only one, and on my very first laser can I?

3. If my divergence truly is as large as I think, and with the other G9 lens too, then is diode replacement the only option? My module is press fit, and that is going to be a nightmare!

Wmacky said:

Still in the testing mode of my new 9mm 445 build. I'm new to multimode, and wonder if there is divergence variation with this diode like there is with output? I'm getting a 8" in focus line at about 75' to 80'. This with a G2 lens. Does this sound about right?

Click to expand...

From this old thread. http://laserpointerforums.com/f49/lfl-long-focal-length-g2-lens-81454.html That lens has a focal length of 4mm. That is a short focal length. That will cause a high divergence. A longer focal length lens will solve that.

I stole this image from DTR to use as a reference. When you say the spot/line is a certain width, it's hard to know just what that means. The spot intensity will diminish away from the center, but at what point do you define the edge? For a brighter spot, you may subjectively define the observed edge at a much wider distance than you would for a similar but dimmer spot. Does yours look like this with the dim box around the central line? is 8" the width of the brightest central spot/rectangle, or the wider thinner line at the top of the dim box? The slow axis on these diodes actually diverges more quickly once collimated since the collimated width is less than that of the fast axis, so the wide and narrow axis will swap at some distance. To get a good measure of divergence you should use 2 distances well past the Rayleigh range, say 100 and 200 feet. Since the intensity of the further spot will be decreased, it may look smaller then it actually is, so some people report lower divergence numbers then you would get if measuring a more objective D4σ width using a beam profiler. So, your divergence may very well be nominally the same as others with this diode and lens with no culprits at all. But, if you are not satisfied with the beam characteristics, the options are to use a different diode altogether - a much lower powered single mode for example, or different optics that give a larger collimated beam. I am currently working on the latter solution, but is is difficult to find the combination of low cost (nobody wants to pay $200 on a lens for a $70 diode), high numerical aperture (to capture all of the light and keep losses down), and large focal length (to get a larger, less divergent beam), along with apsherics (to reduce spherical aberrations that result in more "splash" in the collimated beam). I have some lenses ordered that might fit the bill and will post my findings in the optics section of the forum once I am able to test them out in a week or 2.

Sorry for the double post, but I forgot to ask. Can you take a picture of your spot at that distance to help us determine if it is "normal"? Also, I am assuming you have already read the sticky http://laserpointerforums.com/f65/there-something-wrong-my-beam-spot-59400.html, but if not then it's a good thing to check before getting worried that your laser is broken.

KrowBar said:

Sorry for the double post, but I forgot to ask. Can you take a picture of your spot at that distance to help us determine if it is "normal"? Also, I am assuming you have already read the sticky http://laserpointerforums.com/f65/there-something-wrong-my-beam-spot-59400.html, but if not then it's a good thing to check before getting worried that your laser is broken.

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I have read that article, Thanks, and Ill also try some pics tomorrow.

As to those pics from DTR..... Hmmmm. I don't remember seeing anything exactly like that. ( Very long thin line, with center rectangular spot? I'll need to reconfirm I guess. The 75' shed shot was kinda far away, and closer views have been with protective glasses, and I only see the spot.

BTW, I know I can get a better beam with the 3 element lens, but I still want to determine if my beam is normal, (when using the G2). I don't want to just bandaid the issue and possible settle foe somewhat more divergence that others get.

Also, Yeah I know this multimode 445 won't have the greatest divergence, but I just don't want to get stuck with a mRad8 when everyone else is getting a 2 or 3! I'm very happy with this diode otherwise, and just want to be sure I'm getting the beat beam it can offer. Being new to lasers isn't help much either.........

If it's a press fit, then you could also not have the diode properly seated into the hole