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Thread: what's inside the several watt laser modules?

  1. #1
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    Default what's inside the several watt laser modules?

    I've lately become very interested and started learning more about the inner workings of my laser projectors. One question has came to my mind lately. I understand now there are two main ways a powerful beam can be produced in laser modules used by projectors: powerful several Watt ir diode in DPSS modules and knife edge arrays and corrective optics in several watt diode modules. I haven't really seen ir diodes over 10W and considering the power loss after the conversion process in DPSS modules I'm guessing the 5W+ modules are mainly done with knife edge arrays of visible wavelength diodes. Am I right? The minimum 5mm beam diameter and the shapes of the module boxes seems to suggest that. If anyone has a photo of some few Watt module opened that would be interesting to see too. What I've learned so far has been helpful. I realized the issue with one of my "dead" green modules. It was just the PSU

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    ... I have several fibercoupled IR-diodes with 9W and 25W - the 9W-diodes are single emitters, fed into 105-fibers.

    One type of the 25W-diodes is combined from 3 9W-emitters with knife-edging into a 105-fiber too, the other type is a multi-bar wit 19 emitters in an array and 19 individual fibers attached to every emitter and then combined to an output-bundle with roughly 0.8mm diameter.

    Look here on the opened diodes: http://www.reprap.org/wiki/Laser_Cutter

    ... but this can be a bit more complicated too: http://forums.reprap.org/read.php?13...211#msg-365211

    Viktor

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    Thanks.
    I don't know much about fibers. However, is this relevant to visible wavelength modules used in laser projectors?

    I've seen some custom builds using visible diodes knife edged to get up to 11W, but don't know how close they are to commercial diodes.


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    Your questions are difficult for me to answer. You seem to be shifting from an interest in one kind of laser to another. If your main point is how the laser sources in your projector are constructed it would be best to determine how powerful they are. IR diode pumped DPSS lasers are constructed in sizes from 500mW to hundreds of watts and the way these diodes are interfaced depends on the power.

    The visible diodes are all commercial. Some are harvested from other products and repackaged for laser projectors and others are purchased new from manufacturers or distributors. Depending on the power levels these are combined with polarization optics or small right angle beam directors or both.

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    Quote Originally Posted by planters View Post
    Your questions are difficult for me to answer. You seem to be shifting from an interest in one kind of laser to another. If your main point is how the laser sources in your projector are constructed it would be best to determine how powerful they are. IR diode pumped DPSS lasers are constructed in sizes from 500mW to hundreds of watts and the way these diodes are interfaced depends on the power. The visible diodes are all commercial. Some are harvested from other products and repackaged for laser projectors and others are purchased new from manufacturers or distributors. Depending on the power levels these are combined with polarization optics or small right angle beam directors or both.
    Hi. Thanks. I'm only curious about laser modules inside laser projectors.

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    Okay, I think I wasn't very clear, so please let me explain again.

    I've seen some articles of building several Watt lasers by combining diodes with knife edge arrays. Laserman's site is especially great resource with photos of his builds and explanations.
    I've also learned how DPSS lasers work from Sam's and I believe Laserman's sites.

    Now after learning all this I have few questions.

    1) Are commercial several watt "modules" made the same way? Knife edging, polarization cubes and correction optics?
    2) How are 10W+ commercial visible wavelength DPSS modules made? The most powerful ir diode I've found is 10W. Because of the power loss during the conversion process seems to me like a >5W DPSS module has to use knife edging too.

    Now the reason I'm curious about these is I want to build a powerful laser myself (inspration: https://www.youtube.com/watch?v=4wzM0RLjOSE ) and want to know if
    1) it's financially more reasonable to combine several visible diodes beams with knife edging ( https://sites.google.com/site/dtrlpf/home/diodes ), or try a DPSS build, or if there's even some other practical method I'm not even aware of?
    2) Will a beam created with a knife edge and beam expander build or home DPSS build be anywhere as good (by good I mean brightness and divergence) as the "commercial" ones I've seen on youtube? ( https://www.youtube.com/watch?v=TgZknd1j8-E )

    As for the question why I want to have a several Watt tight laser beam at home, as this dude on youtube said, "this thing is so stupidly powerful there's really no reason to own one but I felt like building one anyway".

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    That helps a lot. I will stick with the DPSS lasers because the red and blue (and recently now even some green direct diode lasers) are well explained elsewhere and frankly are really straight forward. You set up as many diodes as you choose, collimate each beam just as it leaves the diode and use small mirrors or prisms to fold each beam closely next to its neighbor to build up power as the beam grows fatter. They are basically all the same.

    Take a look at my YouTube video about how I built a DPSS laser. This will save some time in explaining this option to get a laser. You may then have additional questions.

    https://www.youtube.com/watch?v=Pp9hliLJjg4

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    Hey, thanks for linking to your video and channel. Very interesting and in-depth.

    But before getting into the DPSS field I would love to talk some about diode based modules. I've certainly read some great articles and explanations on the internet, but even though they explain very well how beams can be combined, the ones I've come across don't have enough info for me about the following :

    1) How to shrink the “beam” (beam array) after you stack them next to each other.
    I've read “beam expanders” are used. But what kind of lenses, and how to know what size, etc. lenses you need and how should they be arranged.
    Also some suggest “cylindrical lenses” ( http://optlasers.com/en/14-cylindrical-lenses ). Same question as with spherical lenses. And also while it seems good for shrinking the combined beam in the X axis only I'd like to know how much you can shrink and how to calculate that.
    And again same questions with using prism pairs.

    2) Cooling. Some say overheating is not an issue with diode setup when heatsinks are used while others say they use TEC coolers.
    I don't know who is right, all I can say is I'd be surprised if a 1-3W diode would run okay for a while with just a heatsink. But then again I haven't made a >1W module myself so what do I know.

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    Don't worry about cooling, yet. A heat sink will be enough until you know significantly more and are trying to push limits.

    Manipulating the beam dimensions of a single beam and tight bundle of multiple beams is very similar. Again, the need to decide when to use particular FL lenses and when to use a prism pair vs a telescoping lens pair is not too important when you are beginning.

    If you go ahead and suffer through the other videos on my channel, you will find that a number of these issues are clarified. It will be a rough night, I know... but then you asked.

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    Quote Originally Posted by planters View Post
    Don't worry about cooling, yet. A heat sink will be enough until you know significantly more and are trying to push limits.
    What limits are you referring to? Close to the maximum operating current/voltage? if you mean this, then I probably won't want to experiment and risk the expensive diodes. If you meant something else, please tell me.

    If you go ahead and suffer through the other videos on my channel, you will find that a number of these issues are clarified. It will be a rough night, I know... but then you asked.
    Yeah, I'll admit I didn't check out all the videos on your channel. Okay, I'll have a look, thanks. If something remains unclear to me I'll come back here and hope you'll be around.
    Thanks for all the help.

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