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Thread: 2W 808nm diode questions

  1. #1
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    Default 2W 808nm diode questions

    Hi PL,

    I bought a 2W 808nm diode from a Chinese supplier, the cost is about $100 USD. The diode is on a C-mount, installed in a TO-3 case, and the specifications are below.

    Parameter: AL808T2000
    CW output power(Mw): 2000
    Peak wavelength(nm): 808+/-10
    Spectral width(nm):≤5
    Threshold current(mA):≤700
    Operating current(mA):≤2800
    Operating voltage:≤2.2
    Slope efficiency(W/A):≥1.0
    wavelength temperature coefficienc(nm/℃):0.3
    Beam divergency(deg):12/40
    Emitting area(μm):200x1
    Serial resitance(Ω):≤0.25
    Lifetime(h):10000
    Package: TO-3



    I ran the diode at a low current using a die4drive and took a photo of the emission pattern (above). The long axis of the emitter is horizontal in this photo.

    I have a couple of questions...

    1) From the divergence specifications and the emission pattern, I suspect that this diode has a FAC lens installed. However, I can't see any separate lens component, so I assume the FAC must be bonded to the diode facet. Is that typical?

    2) Why does the emission form two stripes? I was only expecting one.

    3) For C-mount diodes, why is the anode most commonly connected to the case? This seems counterintuitive, because it requires a negative power supply rail when the case is grounded.

    4) I realise this diode is intended for pumping YAG, where the beam shape is non-critical, but I want to focus the emission to a small spot for laser marking. Is a single plano-convex lens a reasonable way to do that?

    As always, any and all input is welcome!

    Best regards,

    weartronics
    Last edited by weartronics; 05-05-2009 at 04:41.

  2. #2
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    Default

    1) Yes, looks FAC'd. The FAC is a very thin (200um or so) piece of glass fiber in the long axis of the emitter face)
    Under magnification (power off and diode preferably shorted) you should be able to see the fiber and glue dabs where it is attached some distance either side of the die.
    2) These diodes are multimode in the long axis of the emitter. The end result is you will have an array of closely spaced vertical stripes. As the drive current changes more stripes may appear or existing ones move as the modes change.
    3) This is due to the construction of the die. The cavity is fabricated on the anode side of the die. Thus the die chip must be soldered anode down in order to cool the cavity. All high power single emitter 808s and 808 bars seem to be constructed this way. If you don't like common anode an insulated sub-mount would be possible (see 'silver bullet") unfortunately these all seem to be constructed using BeO ceramic which put some people off using them since BeO is nasty stuff if powdered.
    4) To get a spot of similar size to that emitted by the FAC (200um?) simply put a lens twice its focal length from the LD FAC. Another twice the focal length from the lens you have your optimum spot for machining.
    Just make sure your lens is larger diameter than the unfocused beam from the FAC at 2xFl where you would want to insert it.

    Best regards,
    Robin
    Lasers and beer don't mix. After 2 beers I lose coherence.

  3. #3
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    Default

    Hi Robin, that explains everything - thanks!

  4. #4
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    I was just going to post that in my experience more lines will appear as the currecnt goes up and it will look like single 'square' output, but it looks like uk-laser has that covered!

  5. #5
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    Hi

    This is a 2 watt 9mm notice there is no lines in the output this diode does not have a FAC lense one piture is high power and the other is low. cool diode BTW what are you going to use it for
    Attached Thumbnails Attached Thumbnails PICT0054.JPG  

    PICT0055.JPG  

    The glint in your eyes .....
    the warmth and the light ....
    is everything you love ...
    burning right before you ...

  6. #6
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    Hi ionlaser555, thanks for the photos, it is an interesting comparison with/without the FAC lens. I am planning to use the diode for laser marking of dark-colored materials (wood, leather, plastic) etc...

  7. #7
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    looks like a snoc tony diode from ebay
    Do not look into laser with remaining eye
    Need laser repair contact me !!!!!!

  8. #8
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    2800mA for a 2w diode ? isn't it too much ? ( I think it run about 2000mA...but ! )

  9. #9
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    Quote Originally Posted by weartronics View Post
    Hi ionlaser555, thanks for the photos, it is an interesting comparison with/without the FAC lens. I am planning to use the diode for laser marking of dark-colored materials (wood, leather, plastic) etc...

    Cool , how are you running the diode what source are you using to power it.


    Thanks
    The glint in your eyes .....
    the warmth and the light ....
    is everything you love ...
    burning right before you ...

  10. #10
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    Quote Originally Posted by ledfreak3d View Post
    looks like a snoc tony diode from ebay
    Correct, this particular diode is from "snoctony" on eBay, it is the cheapest and easiest source for just one diode. He also has a web site http://www.snoctony.com/, though I don't know what products he manufactures, I think he is mostly a reseller. The C-mount in a TO-3 case is very common, it can be purchased with various power levels from many suppliers.

    Quote Originally Posted by ionlaser555 View Post
    Cool , how are you running the diode what source are you using to power it.Thanks
    I am using a modified die4drive (http://www.die4laser.com/dvd-rec/Die4Drive.htm). If you ask Robin, he can supply a version which runs from 3.3V (dissipating less power), and it can happily run diodes up to 3A or more with appropriate heatsinking.

    Best regards,

    weartronics

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