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Thread: 445 Different wavelengths - possible easy way to find higher wavelength diodes

  1. #1
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    Default 445 Different wavelengths - possible easy way to find higher wavelength diodes

    I was doing some rough alignment on my dual 445 module and noticed something that caught my interest.

    I have ML7 safety glass that are designed to block specific wavelengths. The have OD ratings for 400nm, 532nm, red, and infrared. I have used them for blu-ray and they work very well, but the are def not designed for 445nm.

    The 445 diodes I'm using were bin sorted high efficiency diodes from Krazer and I had them running at about 150mW while aligning the cylinder lenses. When I put on the glasses one of the beams almost completely disappears.

    I assume that the glasses partially block wavelengths a bit higher than the 400nm that they are rated for. So one diode must be a higher wavelength that doesn't get blocked like the other diode. To the naked eye there is not really any difference in color but one beam does look brighter.

    At first I wasn't happy that the two diodes were so different but I guess it doesn't really matter since its hard to notice. Maybe it will will be a good combo to use two slightly diff shades of blue.

    Heres pics:
    This is the two beams:
    Click image for larger version. 

Name:	445 NO FILTER.JPG 
Views:	15 
Size:	39.1 KB 
ID:	24086
    The is the same two beams but with the ML7 glasses used as a filter, the beam that is filtered out is circled in red:
    Click image for larger version. 

Name:	445 FILTER.JPG 
Views:	18 
Size:	71.2 KB 
ID:	24087

  2. #2
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    Default

    I have seen the same thing while aligning a dual 445 under a microscope. Mine was much more noticeable. One beam was definitely a cyan color while the other had the classic BluRay purple tint.

    My safety glasses would almost completely block out the purple beam while I could still see the cyan beam.

    It would be nice to get a projector and compare the beam colors and only use the cyan diodes for projector builds.

    Magman




    Quote Originally Posted by MisterWilling View Post
    I was doing some rough alignment on my dual 445 module and noticed something that caught my interest.

    I have ML7 safety glass that are designed to block specific wavelengths. The have OD ratings for 400nm, 532nm, red, and infrared. I have used them for blu-ray and they work very well, but the are def not designed for 445nm.

    The 445 diodes I'm using were bin sorted high efficiency diodes from Krazer and I had them running at about 150mW while aligning the cylinder lenses. When I put on the glasses one of the beams almost completely disappears.

    I assume that the glasses partially block wavelengths a bit higher than the 400nm that they are rated for. So one diode must be a higher wavelength that doesn't get blocked like the other diode. To the naked eye there is not really any difference in color but one beam does look brighter.

    At first I wasn't happy that the two diodes were so different but I guess it doesn't really matter since its hard to notice. Maybe it will will be a good combo to use two slightly diff shades of blue.

    Heres pics:
    This is the two beams:
    Click image for larger version. 

Name:	445 NO FILTER.JPG 
Views:	15 
Size:	39.1 KB 
ID:	24086
    The is the same two beams but with the ML7 glasses used as a filter, the beam that is filtered out is circled in red:
    Click image for larger version. 

Name:	445 FILTER.JPG 
Views:	18 
Size:	71.2 KB 
ID:	24087

  3. #3
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    Are you certain the glasses are in no way sensitive to polarisation?

    We already know there's quite a variety in wavelength from these 445nm diodes, so I wouldn't be surprised if one of them turned out to be more towards the 440nm and the other would be at the 450nm end.

    Are both diodes from an XJ-A140 projector and, if so, are they from the exact same unit? It's possible Casio puts these diode modules under a spectrograph at the testing department and puts the brightest blues (more towards the 450nm end) in their A140 units, whereas the more violet ones go to the cheaper A130 projectors. It would also explain their difference in rated brightness even though the diode assemblies are running at the same amount of power.

  4. #4
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    apparently the a150s have had teh blue lasers "tweaked" in wavelength according to something i've read.

    we initially thought that meant they deployed the new 460nm nichias, but obviously not...
    Now proudly stocking and offering the best deals on laser-wave

    www.lasershowparts.com
    http://stores.ebay.com.au/Lasershow-Parts

  5. #5
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    I've also noticed a difference in wavelengths, And not through any filters either, but between my arctic laser (Which I don't own anymore) and the 445nm module in my scanner, the module was a fair bit more cyan than the arctic.

  6. #6
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    In this thread I talked about the wavelength shift on LOC diodes and a way we could use that to our advantage in show applications.

    It might be a good idea to look into the wavelength shift of these 445nm diodes. LOC's have a shift of about 0,2-0,3nm/K, so cooling them down will move their emission towards the blue (actually, less red) end of the spectrum.

    If these 445nm diodes also turn out to be shifting in wavelength quite a bit, we could use that to our advantage. However, we need to analyze how much shift there is as a function of temperature. If it turns out to be as much as the LOCs, it's not really worth the effort to run them 50C over ambient if you want to hit 455nm of blue. 25C over ambient with a wavelength of 450nm is doable.

    We might even be lucky and find out that these things have a massive shift, and actually give us good tunability with temperature. I suspect that's wat Casio did with ther A150 series, running the diode assembly hotter than on the A130/A140 after being certain the diodes could survive higher temperatures. That would put the wavelength more towards the 450nm range.

  7. #7
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    So, the hotter they get, the lower the frequency? That's good. I wonder if that's the resonator cavity expanding ..

  8. #8
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    Quote Originally Posted by steve-o View Post
    So, the hotter they get, the lower the frequency? That's good. I wonder if that's the resonator cavity expanding ..
    As far as I know, it is. The 660nm LOC diodes have already shown to do so, and I suspect all direct injection diodes will do the same to some extent.

    The problem is, with 445 you will want a longer wave whereas with red you will want shorter wavelengths. The latter is less damaging on the diodes since cooling them down is no problem, but heating them up can cause a lot of other problems.

    As I said, +25C ambient (somewhere around 50C) would be little trouble for these things, but running 50C over ambient (at about 75C) is going to create some risky situations. It would give you a Watt of 455nm, if these Nichia diodes shift as much as the Mitsubishi diodes do, however.

  9. #9
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    given how easy these are the knife edge, isn't it easier to just combine two diodes than mess with temp control and all that. We have no shortage of power to worry about.

  10. #10
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    Quote Originally Posted by kecked View Post
    given how easy these are the knife edge, isn't it easier to just combine two diodes than mess with temp control and all that. We have no shortage of power to worry about.
    True, but food for thought: A full Watt of 455nm (with the diode running 50C over temp) is a lot brighter than the same Watt at 445nm. Furthermore, the more beams you try to combine with a knife edge or PBS, the more difficult it will be to tame that beam into something useful.

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