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Does there exist a type of LED (or other type of light source) that can change it's wavelength depending on the current/voltage it receives on a second wire? If not, would something like this even be possible?

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    $\begingroup$ Back as a young aspiring electronics guy I would play with LEDs. By turning up the voltage you could get a red LED to turn orange, and then yellow... Continuing onward turned it black and it wouldn't work again (sigh). However, there are bi-directional LEDs that are two LEDs of opposite polarity in parallel. Biasing it one way gives one color, reversing the polarity gives another. Applications involve red/green panel indicators. $\endgroup$
    – Jon Custer
    Commented Aug 3, 2015 at 16:49
  • $\begingroup$ Would Electrical Engineering be a better home for this question? $\endgroup$
    – Qmechanic
    Commented Aug 3, 2015 at 18:11
  • $\begingroup$ @JonCuster Even more and it becomes an NED (noise emitting diode). The color change is mostly due to self-heating of the die changing the band-gap energy. Dunk it in LN2 and the color changes the other way. $\endgroup$ Commented Mar 20, 2016 at 20:10
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    $\begingroup$ @SpehroPefhany - and if you put too much current through it will become an SED - smoke emitting device... $\endgroup$
    – Jon Custer
    Commented Mar 21, 2016 at 1:00

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