SureFire KL-1 and LED Technical Question

[this_is_nascar]

I have a question for you LED technical types out there. When it comes to LED's, I consider myself a user, without any technical where-with-alls. This is why I'm asking this question to you.

Is it possible that the longer an LED is used, the tint changes? The reason that I'm asking is that I think I'm finding my KL-1's losing some of the blue/violet tint as I use them more. Is this possible or is it that I'm just getting used to them?

 

[MicroE]

Nascar---The wavelength of the LED is fixed by the bandgap of the semiconductor materials. (We'll skip the quantum mechanics stuff here.) That is, once you make the diode it's wavelength can't change. It's wavelength is fixed by its ingredients.
Now, having said that, I should mention three possibilities that jump to mind.
One, the wavelength is temperature-dependent. This SHOULD not be an issue for you because the LED should reach it's steady-state temperature rather quickly. The heat-sinking should be sufficient to keep the LED at a steady temperature during use. If heat-sinking is a problem the wavelength can drift.
Two, the wavelength can change with age if there are crystal defects or other items that could change the semiconductor over time. For instance, contaminants in the crystal may migrate to the diode junction over time and change it's characteristics Once again, this SHOULD not be a problem for you. I assume that the people at Luxeon have a nice, clean, controlled fab.
Three, the wavelength can shift if the phosphor is changing. The white LEDs are, as you know, actually blue LED's with a coating that absorbs some of the blue and retransmits it shifted to yellow. The phosphor is VERY tempermental and may change over time. The people at Luxeon seem to be having tremendous difficulty getting the phosphor correct. IF there is a prolem (and I am NOT saying that there is a problem) with your device the phosphor seems like the most likely suspect.---Marc

 

[Wolfen]

I noticied that last night. So I pulled out the other that hasn't been used much and it seemed whiter also. I think I'm just used to the color.

 

[Sean]

I've noticed the same thing. At first the blue hotspot on my KL1 was so annoying, now it's like the blue is more of a light baby-blue with a slight green corona. Looks pretty close to white at any distance.

I've been eyeing up several LS's lately, it seems like once I find an LS that has a more annoying tint, my perspective changes. I would still swear that it's more white than before.

 

[MicroE]

It's starting to sound more and more like this is a perception problem and not a problem with the diodes.