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Thread: Poor Man's Power Meter

  1. #1
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    Default Poor Man's Power Meter

    As many here know, I have been working on some high energy pulsed lasers. Each time I come up with some bright idea, I can test the effect spectrally with an attenuated spectrometer. I can test the pulse duration and the RELATIVE power with a biased photo diode sent to an oscilloscope. The problem is determining the absolute energy in a single pulse.

    I built a calorimeter based on a small aluminum light trap supported in a vacuum. It sounds like it might work, but the range of measurement is limited to how fine a temperature differential I can measure and when I get really serious the trap gets hot and has to cool prior to the next reading. This means dumping the vacuum and so on.


    So... I was trying a new converter dye and decided to see if the beam got any warmer than it was before. I mean how good could it be? So, I used my hand. Yep, that's what I did and the converter was good, really really good. Despite my cat like reflexes I didn't manage to pull my hand out in time. An entire civilization disappeared in some nearby universe between the pulse and my awareness of the pulse. There was a loud snap and the plume was bright because the laser goggles don't protect you from a broad-band black body. It may have actually damaged the surface of the output coupler as the acetone and the methanol along with the optical wipes are not removing the splatter. I could use some suggestions here.

    Anyway, and the hand? Well, there is a nice 3cm (exactly 3.0cm diameter grey circle covering a blister. And boy does it hurt. This is serious stuff. You would not want to trust goggles to a direct hit from this thing. I don't know what kind of power it is outputting, but the Cynosure V beam I used to operate would do this kind of damage ( maybe a bit less, I can't remember for sure, but this really hurts) at around 10J/cm^2.

    This is a little like getting a speeding ticket in a Ferrari. It hurts, but I can't help smile a little. At least the ticket says how fast you were going. Oh well.

  2. #2
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    Seriously, do not burn skin with lasers! Mutated DNA, RA rarRa RA....
    This space for rent.

  3. #3
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    Any post that includes the phrase "despite my cat like reflexes" is going to be humorous.
    "Help, help, I'm being repressed!"

  4. #4
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    Sorry, any post relating to amateur laser surgery just is not on.

    I am now forced to take hiatus from this forum.
    This space for rent.

  5. #5
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    Did somwun menchun cats?

    @ "This is a little like getting a speeding ticket in a Ferrari."

    I wont wun of dem fings !
    Cheers
    PS. @"There was a loud snap " reminds me of 20w argon on my finger nail ...I heard the "sizzle" before the pain hit !
    Last edited by catalanjo; 10-21-2015 at 05:25.

  6. #6
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
    Infinitus Excellentia Ion Laser Dominatus
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    We professionals use a quartz wedge at a low angle of incidence to split off a signal over to a Joule meter head..

    I've been buying heads off Ebay for 50$, I'll see if I can find you one. Readout is an oscilloscope..

    Steve
    Qui habet Christos, habet Vitam!
    I should have rented the space under my name for advertising.
    When I still could have...

  7. #7
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    " 15 characters"
    Last edited by Laser Wizardry; 11-13-2015 at 12:58.

  8. #8
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    I DO know something about laser surgery, but the best to do regarding that reference is to move on ( or back) to the OP. Putting a body part especially not an enemy's body part in front of a laser is something we all do when aligning optics and blocking a beam. But, at the risk of going against convensions, all lasers are not the same. A 1mW alignment laser is not the same as a multi- watt diode or ion. Which is not the same as a 20 MW pulsed laser (maybe even more). First protect the eye then the skin and then structures. I needed this reminder and wanted to share it. The ointment helps.

  9. #9
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    laser burns sometimes have a way of turning cancerous.
    You and dnar made comments about this. I am not aware of this special risk. Other than the threat by PAH compounds that can result from burns of any type, is there a specific risk associated with non-ionizing laser energy?

  10. #10
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    ... I removed some warts with focussed sunlight ... the first one some +45 years ago

    And for precise temperature measuring - some years ago we've developed a super accurate temperature controller with +/- 0.002 degC PID-oszillation, based on NI200 or PT100 sensors and 24Bit-ADC (ADuC847 microcontroller) ... could be eventually shared, if you're interested in cooperation ...

    Viktor

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