Possible risk 3 elements with high power lasers!

Hi guys just a quick one.

I would not recommend using a 3 element with a NUBM07E diode, or any other high power diode for that matter. I just finished a custom build in a Sinner Phobos and the diode was set a exactly 4 A with an SXD. I have never used a 3 element with these diodes, but thats what the member wanted. The beam looked very good when I set up the focus and all was working well until I tried to LPM it. At that point it hit 700 mW and I thought maybe my LPM was messing around. Shining it in the room however confirmed this as the beam was barely visible. The power dropped to 400 mW with a G9 and 200 with a 3 element.

Moral of the story do not use 3 element lenses with high power diodes. To be honest I wouldnt have done it, but for the posts in the forum where people said they have actually used them. I never actually liked the idea of a 3 element with an M140 let alone one of these diodes, due to the possibility of back reflections, but I guess I got complacent. :beer:

Re: Do not use 3 element lenses with high power lasers!

Yea 3 elements have there place. That's all I ever use But I'm a low power guy. 3 elements give a better beam But they do this by chopping off some of the light. Give me beam over power any day.

Re: Do not use 3 element lenses with high power lasers!

grainde said:

Hi guys just a quick one.

I would not recommend using a 3 element with a NUBM07E diode, or any other high power diode for that matter. I just finished a custom build in a Sinner Phobos and the diode was set a exactly 4 A with an SXD. I have never used a 3 element with these diodes, but thats what the member wanted. The beam looked very good when I set up the focus and all was working well until I tried to LPM it. At that point it hit 700 mW and I thought maybe my LPM was messing around. Shining it in the room however confirmed this as the beam was barely visible. The power dropped to 400 mW with a G9 and 200 with a 3 element.

Moral of the story do not use 3 element lenses with high power diodes. To be honest I wouldnt have done it, but for the posts in the forum where people said they have actually used them. I never actually liked the idea of a 3 element with an M140 let alone one of these diodes, due to the possibility of back reflections, but I guess I got complacent. :beer:

Click to expand...

You were using optics that do not have the appropriate AR coatings. There's a world full of optics companies, but I have no idea why ever everyone automatically buys the ones you used.

Re: Do not use 3 element lenses with high power lasers!

The lenses are usually chipped around the edges. I prefer the 2 element lens for beam quality of blues and greens. The g7 is nice but the design needs to have the lens into the barrel more than it is now. My 3 element lens are just being stored. I don't use them at all. Sucks your diode scrapped out.

Re: Do not use 3 element lenses with high power lasers!

steve001 said:

You were using optics that do not have the appropriate AR coatings. There's a world full of optics companies, but I have no idea why ever everyone automatically buys the ones you used.

Click to expand...

Nope it was a 3 element coated for 400 - 500 nm and the diode was a 465, so it should have been fine...:beer:

Re: Do not use 3 element lenses with high power lasers!

I always use 3 element. I used it on an Nubm44 and in worked great just ask electric plasma but I'm sure g2 would've had more power.

Re: Do not use 3 element lenses with high power lasers!

Crazlaser said:

I always use 3 element. I used it on an Nubm44 and in worked great just ask electric plasma but I'm sure g2 would've had more power.

Click to expand...

Your choice I am just warning you that there is a high risk of back reflection, which will kill your diode! I personally wont be doing that again.:beer:

Re: Do not use 3 element lenses with high power lasers!

dden4012 said:

The lenses are usually chipped around the edges. I prefer the 2 element lens for beam quality of blues and greens. The g7 is nice but the design needs to have the lens into the barrel more than it is now. My 3 element lens are just being stored. I don't use them at all. Sucks your diode scrapped out.

Click to expand...

I havent actually tried the 2 elements, I probably still wouldnt use them with high powered diodes though. Yep it does suck lol :gun:

Re: Do not use 3 element lenses with high power lasers!

Crazlaser said:

I always use 3 element. I used it on an Nubm44 and in worked great just ask electric plasma but I'm sure g2 would've had more power.

Click to expand...

Yep the 3E in the nubm44 I got off you was completely fine. Though I did end up swapping it for a G2 and a 3x BE, rebuilt it in a different host. Build thread coming in the near future! :wave:

Re: Do not use 3 element lenses with high power lasers!

grainde said:

Hi guys just a quick one.

I would not recommend using a 3 element with a NUBM07E diode, or any other high power diode for that matter. I just finished a custom build in a Sinner Phobos and the diode was set a exactly 4 A with an SXD. I have never used a 3 element with these diodes, but thats what the member wanted. The beam looked very good when I set up the focus and all was working well until I tried to LPM it. At that point it hit 700 mW and I thought maybe my LPM was messing around. Shining it in the room however confirmed this as the beam was barely visible. The power dropped to 400 mW with a G9 and 200 with a 3 element.

Moral of the story do not use 3 element lenses with high power diodes. To be honest I wouldnt have done it, but for the posts in the forum where people said they have actually used them. I never actually liked the idea of a 3 element with an M140 let alone one of these diodes, due to the possibility of back reflections, but I guess I got complacent. :beer:

Click to expand...

Curious, What you are saying is every high powered unit that Sanwu has made with a 3 element lens is susceptible to early organ failure? :thinking: Any chance it was just a weak diode?? or something else?

Re: Do not use 3 element lenses with high power lasers!

Yea I feel there is more to this. How did you determine it was the lens that killed it? If it had the proper coating it should be fine right?

Re: Do not use 3 element lenses with high power lasers!

I had that same diode die on me too, but using a G2 lens and it did the same thing, went down to low output but with a dark slice in the middle of the beam after that. I believe we cannot drive them at 4 amps, probably better at 3 amps. Mine died at 3.5 amps.

Re: Do not use 3 element lenses with high power lasers!

I have seen several NUBM07E diodes get weaker and weaker, every single one was run at 3.5 amps and had the GBall/can removed, I think the problem is oxygen, but I have not done a comparative study with a GBall intact diode, but I speculate that they would retain brightness longer with the GBall/can left intact.

-----edit-----

Ha, I remember looking at the raw output of the last 07 I had while the GBall was intact and it was mounted in a heatsinked HH of course, then not a day after removing the GBall/can I pulled the G7 lens I was using and noticed a dark line in the raw output. That diode also got weak in short order after the GBall/can was removed.

My NUBM08 lasted 6 weeks to about half brightness ( estimated ) , it lost it's burning ability over the weeks as I burn at a 20-30 foot distance often and I remember it got harder and harder to make it light a paper bag, but when I put a NUBM44 unit on the task " poof " up in flames no problem, and this NUBM44 has a 3 element it's been wearing for months along with a 3X expander, before that it had a 3 element for months and did just fine. BUT the NUBM44 is a can/window diode.

Re: Do not use 3 element lenses with high power lasers!

Wish I knew if the manufacturer fills them with inert gas, but for that to work the GBall lens would need to have an air tight seal. If we knew that, we would know if oxygen is the problem or these diodes just don't like to be run so hard.

Re: Do not use 3 element lenses with high power lasers!

BobMc said:

Curious, What you are saying is every high powered unit that Sanwu has made with a 3 element lens is susceptible to early organ failure? :thinking: Any chance it was just a weak diode?? or something else?

Click to expand...

Well the laser was working fine during the build and once completed. I finished it up and put the 3 element on. It was running for a max of 30 seconds, whilst setting the focus and everything was fine. It was very bright. About an hour later I went to LPM it and switched out some fresh batteries (18350s fully charged). Before that I had used some 16430s at 4.17 V the later batteries are older with a slightly higer internal resistance and with a tail cap current of 2.6 A, although both IMR, they sag more. Jordan states that:

Again it is to be Noted and payed attention that the ROLLBACK will be at a different point if your diode is at a different Temp then what i show. Pretty much anything above 5A is not recommended IMO and with 4.5A being the MAX... The typical roll back i noticed is around 5.5A-5.8A at 25C. So if your experimenting to get that extra 1 or 2nm out of the diode just pay attention. I do know that at least for this diode it wont die up to 5.8A... Past that i do not know. Dint want to push it until i get more diodes in.

Click to expand...

This means that setting it at 4 A should not have been an issue. I suppose it is possible that I got a weak diode from him, but if I did and that was the cause we would have to rethink the safe max current for this diode. As there is a lot of data confirming that these diodes are ok at or above this current, I don't think this is the problem. FYI to set the current I use a modified test load to set it initially, I then check by wiring the driver up in series with a single 1 Ohm 50 W resistor, which acts as the load - This usually gives a very similar result. Once I'm sure the driver is pushing out around 4 A, I solder everything up in series with my PSU and DMM (10A mode) and check the real current to the diode from the driver. Normally due to the errors in the other methods, I normally find that the diode is driven at approx 5 - 7 % below the current I'd set. Using the pot and watching the DMM display this can be very carefully corrected up to the desired current, in this case 4 A. You have to be careful doing this ie don't turn the pot too far. In my case I went up to an absolute max of 4.089 mA, read with my Fluke 87 III, before correcting it to exactly 4.001 mA.

10fenny said:

Yea I feel there is more to this. How did you determine it was the lens that killed it? If it had the proper coating it should be fine right?

Click to expand...

Yep should have been? :thinking:

Re: Do not use 3 element lenses with high power lasers!

I am having trouble finding the article I read before. But basically oxygen degraded the barrier layers built into the igan substrate but larger molecules such as nitrogen did not. I will try to find the article. There was also the refractive index of the oxygen erodible barrier layers that can be used to increase the output of the substrate the way brag grating works, but again it's sensitive to oxygen.


http://www.academia.edu/3885975/Properties_of_InGaN_blue_laser_diodes_grown_on_bulk_GaN_substrates

Studies on the photodegradation of red, green and blue phosphorescent OLED emitters