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Thread: 638nm vs 637nm (single mode vs multimode)

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    Default 638nm vs 637nm (single mode vs multimode)

    Hi all,

    I have now seen suppliers challenging us to tell the difference between their single mode and multimode red beams, and Evil Laser's Kore is a high quality projector utilising multimode red. How would 1.5W 637nm fare vs 2.5W of 638nm in terms of visibility? Picture the scenario at an outdoor festival over the heads of the audience. Assuming both have been built to more or less their full potential of what is optically possible, and the 638nm does not have any spatial filtering. Beam characteristics roughly the same at 1mrad and 5mm x 5mm, perhaps the multimode a bit higher, and obviously with wings.

    The dilemma is I have 2x 10W green/blue projectors and am looking for a small amount of red to add to them. I am not looking for a balanced white, just a touch of red to make them more versatile for the smaller shows that require full colour.

    Thoughts and opinions all appreciated.
    Last edited by Humphry; 09-08-2015 at 08:17.

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    I'm sort of interested in the replies to this as well. I see a huge difference in price on raw modules between 637 and 638 and wondered how much of a difference is there really.

    Take for example 3w of 637 here: http://goldenstarlaser.com/index.php...product_id=207 for $5000 versus

    3w of 638 here: http://goldenstarlaser.com/index.php...product_id=243 for $1,200.

    Is 637 really $3,800 "better"?
    PM Sent...

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    here's a 637 / 638 pic that was recently posted to facebook.

    Click image for larger version. 

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    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

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    In your example clearly the higher power one is going to be better.
    Providing the multi mode module uses some form of correction, preferably cylinders, it's going to be very close, even if the powers are equal.
    Spatial filtering is not the be all and end all either. I get very good results simply masking the top/bottom wings with aluminium tape on the cylinders.
    I am still unclear why people are persisting with large arrays of single mode diodes, the engineering challenges and cost far outweigh the benefits (imho)
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    You are using Bonetti's defense against me, ah?

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    Hi all and thanks for your responses, much appreciated. Very interesting insight about there not being a noticeable difference, even for the same powers. (assuming similar beam specs). I look forward to hearing more thoughts on this highly variable and perhaps controversial subject

    Quote Originally Posted by norty303 View Post
    In your example clearly the higher power one is going to be better.
    Providing the multi mode module uses some form of correction, preferably cylinders, it's going to be very close, even if the powers are equal.
    Spatial filtering is not the be all and end all either. I get very good results simply masking the top/bottom wings with aluminium tape on the cylinders.
    I am still unclear why people are persisting with large arrays of single mode diodes, the engineering challenges and cost far outweigh the benefits (imho)

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    Well, if you're looking for a difference because of wavelength, there is unlikely to be one, given the variation in wavelength inherent in the individual diodes. 638 could just easily be 636 in the real world and you're unlikely to notice any difference in one or two nm
    Frikkin Lasers
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    You are using Bonetti's defense against me, ah?

    I thought it fitting, considering the rocky terrain.

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    No I wouldn't think wavelength would make a major difference. I am thinking about clarity of the beam. But I am quickly realising that build quality is probably the biggest variable here..

    Quote Originally Posted by norty303 View Post
    Well, if you're looking for a difference because of wavelength, there is unlikely to be one, given the variation in wavelength inherent in the individual diodes. 638 could just easily be 636 in the real world and you're unlikely to notice any difference in one or two nm

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    Yeah, I don't see $3800 difference in that particular example. Yes, I get the square versus round and so forth but, as Norty said, I suspect color is pretty darn close. You're likely not using 3 watts of red for graphics anyway (in my sample) and if you're mixing it with big multimode blue and big multimode green, aren't things going to be relatively similar in terms of beam properties to a degree?
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    if you were to see a quality single module red module, RGBlasersystems or arctos for example there is a real difference from multi mode

    single mode offers a much more dense beam
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    I've not seen that myself Andy. My 6 banger Kvant was no more dense than a pair of cubed and corrected P73.
    Frikkin Lasers
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    You are using Bonetti's defense against me, ah?

    I thought it fitting, considering the rocky terrain.

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