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Thread: Pioneer 112 Results (red Hot)

  1. #51
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    Sep 2007
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    Hi Andyf97, I mount the diodes in basically a fairly big aluminium block which helps suck the heat away from the laser chip, I have not really got into peltier coolers maybe one day but for the moment it is unnecessary for me. Most frequent damage is done to the chip face when going well above the specified current levels recommended by the laser manufacturer. Obviously cooling by external means would help reduce this but inevitably if you crank up the power enough the chip literally cooks itself from the inside destroying the polished output face. The only temperature checks I have done with pioneer diodes was on the outside of the aluminium block which realistically is no good as the diode temp could be 20 to 30 degrees hotter than this, as you have seen for your self the little wires that connect up the diode for power can melt this is more of a manufacturing fault more than anything as the wire should be made to the correct tolerance levels to take the current that is applied to the chip, again cooling and using a inert gas would help to what degree I have know idea but high power pump chips are cooled for that reason as it would not belong before you had a thermal run away condition, I would be very surprised if running the diodes at the manufacturers guide line maximum would melt the wires but I am no expert in such matters. Nice shows by the way.
    Paul

  2. #52
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    Nice mod there Survey, it certainly looks the part what sort of beam specs do you get with that set up, quite good I would imagine, you will probably find that the diode in question (pioneer) will be rated at 350mw pulse that Mitsubishi diode looks quite good it has a good high max working temperature also the fast axis is good also nice find if you don’t mind me asking how much did you pay foe the diode

  3. #53
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    Oct 2006
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    Central Florida
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    Question

    In the auction the seller states you could run these at 600mA with proper cooling, TEC or liquid. Is it possible to run these like an overclocked computer? Can you keep the diode in the proper temp range and add power indefinatly as long as you keep the diode at a safe temp? Just curious.

    I am picturing mounting a CPU TEC/waterblock to the bottom of a diode mount like you would a processor, and try to match TEC power incread, and diode mApmerage to keep the diode at it's prefered temp while upping the output, just like overclocking a computer.

  4. #54
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    Jan 2007
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    Sheepsville, Wales, UK
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    one limiting factor of a diodes ability to produce more power is the COD - critical optical damage level. As Kaz mentioned this is where the power basically fries the mirrors in the cavity. This is a common mode of failure which is caused by other outside effects - This is why back reflection can cause a failure and also why static will kill a diode. The extremely high current from a static flash will turn the laser on for a very short time. this blows the mirrors off and you got yourself a pretty poor red LED.
    The mirrors are so small you have to control how much you throw at them. Some outside influences such as cooling will help but you cant get away from it, drive it too hard and it will cease to lase as there will no longer be a cavity in which lasing can take place.

    Rob
    If you need to ask the question 'whats so good about a laser' - you won't understand the answer.
    -----------------------------------------------------------------------------------------------
    Laserists do it by the nanometre.

    Stanwax Laser is a Corporate Member of Ilda

    Stanwax Laser main distributor of First Contact in UK - like us on Facebook http://www.facebook.com/FirstContactPolymerCleaner
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  5. #55
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    May 2007
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    Portugal
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    Hi Kaz of course I don't mind to tell the cost of the ML101J27.
    I've bought two of them in 2005 and they still lase like the day I bought them.
    By the time ML101J27 was under development, but I've managed that Mitsubishi send me two at a price of 45,24€ (euro) each.

    So I guess that they sent me two prototypes, note that I've never pushed them over the specs of 120mw at 200ma, but compared to another modules I've seen they are realy good.

    The two are combined with a cube that I posted for some time I realy don't Know the coating of such a monster but I guess somewhere around 780nm and they work great, I remember now that I was surprised to see that when I turned one of the diodes by 90º the optical output increased very much.(by the time I don't knew much about polarisation and sum H/V beams).

  6. #56
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    May 2007
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    Romania
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    Here's the data sheet for them, 130mW CW @ 200mA 2V or 350mW pulsed. See note 2 then read Note 1, kind of conflicting Notes.

    http://www.mitsubishichips.com/Japan...nm/ml1xx27.pdf

    I thought came to me, are these pulses for 350mW fast enough for the light to be seen as CW?

  7. #57
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    Sep 2007
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    ,essex, uk
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    Hi Andyf97, the trouble with pulsing the diode (this is what most of the dvd burner diodes are made for) is that by pulsing at say 100 times a second the laser is half on and half off if that makes sense so the average power will be approximately half of that in continuous wave the diode will put out 350 mw but for a very short pulse like the data writing of a dvd when the disc spins it fires the laser 1000’s of times a second to mark the dye on the disc the higher the mw power output the faster it can write to the dvd its as simple as that, if the pulses are long enough say at the over the top amount of 10 a second in-between the laser pulsing there would be nothing unless you made a controller to bring down the diode from say 200mw then ramping to 350 mw at ten times a second so you would have a beam that goes darker and brighter 10 times a second but at such a long pulse length you then run the risk of damaging the laser output face, if you pulsed it at a higher rate it would probably not be seen to pulse but if you wanted to use this method whilst scanning the scan termination would look like lots of dashes and like above if pulsed you would not gain that much of an advantage over cw hope this helps
    Paul

  8. #58
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    yes, its kind of what i was thinking too...it was just a thought that if the pulses could be fast enough, faster than the eye, the power would exist too.

  9. #59
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    May 2007
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    Portugal
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    Fast isn't the problem!
    The "duty cycle" of a repetitively pulsed laser is defined as the ratio of the time the laser is ON to the time the laser is OFF.
    Thus, a 35% duty cycle means that the laser is on for 35% of that pulse, if we consider the pulse width to be 30ns, then one second (1 second) / (30 nanoseconds) = 33 333 333.3 pulses or 33,33mhz if you want.
    So this particular LD could be modulated (in theory) to 30Mhz very fast.
    To do so we need a TTL Pulse Width Generator capable of generating 30ns pulses (independent from input freq.) like the TTLPWG-30 or the TTLPW030 (note that the max freq. input to these ones is 15 mhz) and a switch that puts power to the laser 35% of each pulse (lets say 10.5ns ON and 19.5ns OFF every 30ns pulse).
    As you see it involves a complicated TTL modulation capable of very high frequencies compared to analog or ttl laser supplies that most of us use.

  10. #60
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    Pflugerville, TX, USA
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    Average power is what you will perceive. So, even if it is pulsed you have to average in a 0 for the amount of time that it is off and that lowers the average power considerably. So, pulsing at 350mw is no better than leaving it on continuously at 100mw or so.

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