Re: 6x Blu-ray SLEDS GB! Supply is almost dry! Hur
jayrob said:
The power is still at 154mW's!! This is good news isn't it Igor?
It was at 154mW's 20 hours ago! Maybe as the lens started melting (lol) , it was affecting the reading...
Jay
I do think it is good news Jay!
When i read the testing reports here, i got so worried, that i canceled my third order of 10 more 4x's. Now i regret that.... :-/
This diode has by now outlived any PHR i have ever put through similar testing. It even outlived some PHRs at 100-110mW, when tested the same way.. So i think it is now safe to say that this diode is considerably better than PHRs. 150mW may be a bit much for it, but by now it would have survived a year even in my hands!
I will go check the counter now.. Ok, it says 5174, each count is a one minute powerup, so just over 86 hours!
Not bad for 150mA. When i would test a PHR in the same setup at 150mA, i would get 3-20 hours...
Oh, and yeah, the lens did in fact melt a little. When i visualised the beam this morning, i saw a "hole" in the middle. So i picked it up and played with the focus, and if the focus was outwards from parallel, there was a dark spot in the middle of the enlarged spot. I thought it was a speck of dust, but i couldn't remove it. But when i moved the lens inwards from parallel, the same spot was suddenly brighter, than the rest of the beam. That's when i started suspecting the lens itself.
It is actual damage on the lens from 86 hours of 405nm. I heard that acrylics degrade in UV, but this is the first time i saw it, because it's the first time a diode at this power blasted against a lens for so long. I knew that it could cause a power decline, but i had no idea that it would be visible! It's in the precise middle of the lens, where the beam has the highest intensity.. There is ~23% more power behind the lens - this extra power is wasted only on "baking" the plastic lens..
When i put a fresh clean lens in, the power jumped a little from before, so a part of the power decline came from the lens degrading, and not just the diode. But it was a smaller part. I did always double check the power readings with the "blu" lens, to eliminate things like wavelength drift and lens degradation.
I put this lens aside, cos i want to look at it under a microscope..
Anyway, a part of the power decline did come from the lens, which is good news, cos it means the power has not yet dropped by more than 10mW. but both the diode and the lens degraded gradually over the same time, so the lens didn't just add a 2mW drop all of a sudden, but rather slowly added to it little by little, untill it caused 3-4mW difference and even became visible!
This morning the power was showing only 150mW! Then i switched the lens and it went back to 153-154mW.
I paused the test now, so that i can let it cool off completelly, and measure the "cold power" - the 164mW at the start was the power at 20°C..
EDIT: Cold power is 155mW!
EDIT 2: Something strange started happening while it was running. Sometimes the power would start at only 141mW, then climb to 153-154mW as it warmed up, then it would drop to 150mW as it warmed up more.. The wavelength was changing slightly, but not enough to explain this.
I think that the diode has degraded just enough to fall back into the first kink. It's possible, that the high power was the result of this diode having the first kink lower than others, so 150mA brought it out of it and produced the high power. But as 405nm diodes degrade, they "roll" down their own slope - the threshold could have climbed just enough for 150mA to be barelly above the first kink. When it was at only 141mW, there was a hint of mode hopping present, so it's a possibility.. If it degrades further, i would expect the power to start dropping faster, but due to the kink.
EDIT 3: Indeed, the behavior has now become predictable. The diode has degraded to a level, where it starts in a kink. The only thing i don't understand is why it climbs out of it as it warms up. It should be the other way around..
and the current increases with decline in charge?!? 
