Malkoff        
Results 1 to 16 of 16

Thread: Green luxeon, red filter

  1. #1
    Flashaholic* tylerdurden's Avatar
    Join Date
    Jan 2003
    Location
    Roaming Around - Southern USA
    Posts
    2,083

    Default Green luxeon, red filter

    Just in case you thought LEDs were monochomatic:



    That's a green L1 head shining through a Surefire red e-series filter (F04?). The emitter is producing a small amount of output along the entire visible spectrum, as shown by the few red photons leaking through the filter.

  2. #2
    Flashaholic*
    Join Date
    Apr 2002
    Location
    Boise, ID
    Posts
    2,639

    Default Re: Green luxeon, red filter

    Yep - LEDs aren't monochromatic, they're narrow-band. Green Luxeons have the widest emission band (eeking into the blue part, and easily into the red part of the spectrum).


  3. #3
    Flashaholic* tylerdurden's Avatar
    Join Date
    Jan 2003
    Location
    Roaming Around - Southern USA
    Posts
    2,083

    Default Re: Green luxeon, red filter

    I've seen those graphs before, but I was really surprised at how much red light was being emitted compared to the overall brightness. Just from looking at the graphs I figured the red light emitted would be very dim, but it's actually quite a bit. Running the green L1 at full power with the filter in place, I get enough light to navigate by in a dark house.

  4. #4

    Default Re: Green luxeon, red filter

    I asked the good Doctor Kisielowski (the scientist at work that's working with Lumileds on increased efficiency) about this, he said such light comes from fairly well characterized defects in the crystal. It is something to be avoided. He also said he'd expect it to vary device to device.

    For what that's worth.

    Doug Owen

  5. #5
    *Flashaholic* IsaacHayes's Avatar
    Join Date
    Jan 2003
    Location
    Missouri
    Posts
    5,876

    Default Re: Green luxeon, red filter

    Try this, shine your green L4 at something florecent orange. What do you see? Orange! My 5W green does this quite well.

  6. #6
    Flashaholic*
    Join Date
    Aug 2002
    Location
    HILLSBORO, OR
    Posts
    1,318

    Default Re: Green luxeon, red filter

    A laser is truly monochomatic, since it is a very finely tuned amplifier

  7. #7
    Flashaholic* WildRice's Avatar
    Join Date
    Nov 2003
    Location
    SW Michigan
    Posts
    1,135

    Default Re: Green luxeon, red filter

    green lasers have this effect too. certain dyes will phophoress under high emmissions of green light. they actually emmit yellow light, this mixed with the green look like orange.
    Jeff

  8. #8
    Flashaholic*
    Join Date
    Apr 2002
    Location
    Boise, ID
    Posts
    2,639

    Default Re: Green luxeon, red filter

    [ QUOTE ]
    Doug Owen said:
    I asked the good Doctor Kisielowski (the scientist at work that's working with Lumileds on increased efficiency) about this, he said such light comes from fairly well characterized defects in the crystal. It is something to be avoided. He also said he'd expect it to vary device to device.

    For what that's worth.

    Doug Owen

    [/ QUOTE ]

    So eliminating those defects (and thus, the orange emission) would lead to an increase in output of green light.

    I've seen lumileds presentations that state that the IQE (internal quantum efficiency) of green luxeons is the worst of the InGaN line - something like 1/2 what the blue/royal blue is.

  9. #9
    Flashaholic*
    Join Date
    Aug 2002
    Location
    Stuck in California again
    Posts
    823

    Default Re: Green luxeon, red filter

    [ QUOTE ]
    WildRice said:
    green lasers have this effect too. certain dyes will phophoress under high emmissions of green light. they actually emmit yellow light, this mixed with the green look like orange.
    Jeff

    [/ QUOTE ]

    Er, how exactly could that be? Yellow plus green is yellow-green.

    Dyes that fluoresce from a green laser are emitting a fairly broad band of colors below the original green; I bet the profile often looks like that of the white Luxeon posted above, but shifted further to the right (red) end of the spectrum. That would place the fluorescent "hump" in the orange band.

  10. #10
    Flashaholic*
    Join Date
    Aug 2002
    Location
    HILLSBORO, OR
    Posts
    1,318

    Default Re: Green luxeon, red filter

    Those colored filters you are using are not very narrow band, if you had a narrower band filter with a laser, the light would be filtered out

  11. #11
    *Retired* The_LED_Museum's Avatar
    Join Date
    Aug 2000
    Location
    Federal Way WA. USA
    Posts
    19,418

    Default Re: Green luxeon, red filter

    For really narrow-band filters, you need dielectric interference filters. I do not have a red one though, otherwise I would loan it to you for this experiment since I do not have a green LS LED.

    Edmunds Scientific sells filters like these, in a large variety of passband wavelengths.

    Somewhere around here (unless the cleaners stole or got rid of them in late 2002), I have two shades of green, blue-green, and deep blue interference filters...I just found three of the filters: the deep blue, the blue-green, and one of the green ones. But no red. [img]/ubbthreads/images/graemlins/jpshakehead.gif[/img]

  12. #12
    Flashaholic* Wits' End's Avatar
    Join Date
    Nov 2001
    Location
    Remote NEast Minnesota, next to Lake Superior
    Posts
    2,317

    Default Re: Green luxeon, red filter

    And I looked at this expecting it to be a black light [img]/ubbthreads/images/graemlins/smile.gif[/img]

  13. #13
    Flashaholic*
    Join Date
    Nov 2000
    Location
    Connecticut
    Posts
    1,944

    Default Re: Green luxeon, red filter

    Do 5mm greens also have very broad emmission spectra? Aren't they based on the same die? If so, how could green be used by the military for avoiding NV detection if these LEDs emit so much red?

  14. #14

    Default Re: Green luxeon, red filter

    [ QUOTE ]
    evan9162 said:
    So eliminating those defects (and thus, the orange emission) would lead to an increase in output of green light.

    I've seen lumileds presentations that state that the IQE (internal quantum efficiency) of green luxeons is the worst of the InGaN line - something like 1/2 what the blue/royal blue is.

    [/ QUOTE ]

    As I understand Christian's research, that's exactly the goal. By confining the emissive area to a few (typically under a dozen) atomic layers in the crystal fewer faults are included improving overall efficiency.

    Fun stuff, really. When blue LEDs first came out, he got two at a seminar in Japan and we 'reverse engineered' them. He ground them down to make TEM (transmission electron micorscope) specimens (a dozen or so atoms thick) and figured out how they worked. The rest is as they say, history.

    I've asked him a couple of times to post some of his micorgraphs (photos) of the atomic structure so I can point the faithful to them. Someday he may either find the time or get tired of my asking.....

    Doug Owen

  15. #15
    Flashaholic* tylerdurden's Avatar
    Join Date
    Jan 2003
    Location
    Roaming Around - Southern USA
    Posts
    2,083

    Default Re: Green luxeon, red filter

    I did the same thing with a royal blue luxeon. A LOT less light leaks through. I guess this is due to the better internal efficiency and the tighter emission band of the blue emitters, along with the fact that the emission curve for each emitter is still centered around the emitter's primary color, and blue is further from red than green.

    In any case, there was such a small amount of light coming through the red filter that I was able to look directly into the emitter and see the detail of the die.







    Even better pictures can be found on my web site.

  16. #16
    *Flashaholic* IsaacHayes's Avatar
    Join Date
    Jan 2003
    Location
    Missouri
    Posts
    5,876

    Default Re: Green luxeon, red filter

    cool. I wonder about R/O and a green or blue filter...?

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •