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Thread: Noob searching for info

  1. #1
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    Question Noob searching for info

    Hi,

    I've been reading around the forum for some time now, but there's so much information and it's so disperse that I can't seem to find a lot of the info I'd like to learn about so maybe someone could point me in the right direction.

    These are the main subjects I'm triying to find information about right now:

    - Parts that completely make up a diode based laser module and what things it depends on (color?, power?, type of diode?...).

    - Composition and installation of TEC coolers.

    - Anything I need to know for succesfully building a diode based laser module.

    I feel I'm in a bit of a muddle because of reading too many bits and pieces of information here and there, so any indications you can give me about where to start and which way to go for learning all about lasers would also be much appreciated.

    Thank's.

    Domingo.

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    Hello domingo

    If you want to build a blue or red module with diodes thats posible. Because diodes usually have not enough power by itself so you have to combine them. That is done mechanicly with a setup.The way we combine the diodes in a setup is to stack them. You can stack them on top of eachother vertically of horizontally. When using a PBS to combine two beams you have to have a horizontal polarised beam and a vertical stacked beam and shoot one in the front and one in the side through the PBS. The beamsize of the combined beam is the same as a single beam but has twice the power.
    When stacking the beams, let say 4 the size of the beam gets bigger so you can,t go on with stacking. The thickness of a single beam depends on what diode you want to use and what lens you use to collimate the beam. When having a 1mm beam and stacking 4 then you will end up with a 2x2mm beam at aperture from your setup.

    Because diodes get hot you have to cool the setup. Thats done with a peltier or tec as we call it. The best way is to place the peltier underneath your setup. Most professional companies do that. Here,s my setup so you have an idea how the beams are stacked.Attachment 18802
    Attached Thumbnails Attached Thumbnails P1080618.JPG  


  3. #3
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    Hello edison,

    So what is the maximum beam power you can achieve with one blue or red diode right now? and, is it the same for any wavelength of blue or red or does it vary between lets say 445 and 473 or 635 and 660?

    Also, what about green?

    I don't really understand your explanation about combining the diodes. Are stacking and combining with a PBS different things or are the diodes still stacked when using the PBS cube to combine them?. How exactly are the beams combined when the result is a fatter beam?

    I don't mean to overwhelm you with questions. I really appreciate your effort to try and explain to me, but I'm affraid I'm nowhere near the level of knowledge some of you guys have around here.

    Domingo.

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    The blue 445nm diode can achieve 1 watt of power. The red opencans LPC-815 gives a maximum of 300mw red 650nm. Because 650nm is closer to the infrared you need twice the power when using 640nm diodes.But 640nm diodes are only 150mw. When building a projector you need roughly the same amount of green but twice the amount of red to get white.

    Stacking is done with mounts and mirrors and thats one way of combining beams. The other way is using a PBS. When using a PBS the beams melt toghether so you have the same beamsize as before the PBS. I,m not sure why green isn,t useable in diode form.

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    Quote Originally Posted by edison View Post
    I,m not sure why green isn,t useable in diode form.
    I think it would be very usable to us Green diodes are being commercialised right now using a similar technology to the blue diodes (GaN). But until these are built into pico-projectors, laser TVs or some other mass produced devices, the costs are likely to be prohibitive.

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    But why arent the green diodes in the laserpointer useable, because of the fat beam or divergence?

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    Quote Originally Posted by edison View Post
    But why arent the green diodes in the laserpointer useable, because of the fat beam or divergence?
    Well they're actually infra-red diodes passed through a KTP crystal (i.e. DPSS). The beam characteristics are mostly fine (especially compared with the fat reds and striped blues), it's just the modulation of them that's challenging. Check this out.

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    Quote Originally Posted by edison View Post
    But why arent the green diodes in the laserpointer useable, because of the fat beam or divergence?
    As Taggalucci already mentioned, because green laser pointers are nothing more than standard DPSS lasers that have been made as small as possible to fit in a pointer housing. They are not direct injection lasers like red pointers are.

    Making a DPSS laser small enough to fit in a pointer housing involves trade-offs. Thus, the cavity is inefficient. Alignment is poor. Heat is a problem. Beam quality is often poor. And to top it all off, the driver isn't designed to support any kind of rapid modulation.

    OK, you could take the whole thing apart, mount everything in a larger heat-sink, install a TEC, then hook up a better driver that supports modulation, and maybe install some better optics if need be. Then you'd have to tune the TEC controller to get optimal performance, and you might end up with a decent laser for use in a projector. But by the time you do all that, you're better off just buying a lab DPSS laser and dropping it in place.

    Adam

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    Thanks for the learning curve. You see dpss i,m still learning too. Keep browsing on PL and you will find the right info for building your own module.

  10. #10
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    Yeah!, thanks guys.

    Still, if you know any good sources of info on lasers apart from the forum I'd appreciate you let me know. I supose I'm not the first to mention it, but a few sticky's here and there could ease up the learning curve very much. Maybe the Admin could look into it?, just a thought.

    Domingo.

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