1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

B Combine lasers to make a single strong beam

  1. Jul 10, 2011 #1
    hey i am a total newbie and a beginner in science well i want to know if the following can be done:-:tongue:
    i have a number of laser diodes form dvd drives....
    is there a possible or a certain arrangement of prisms , lenses and mirrors that can be made in order to combine numerous less intense LASER beams to make a single beam that is a lot stronger with minimal energy loss?:confused:
    a single laser diode is good enough to pop balloons , burn paper
    i am just curious to know how much damage a laser beam combined from many diodes can do....:devil:
     
  2. jcsd
  3. Jul 10, 2011 #2

    Drakkith

    User Avatar

    Staff: Mentor

    Easy. Just focus all of the lasers at the same spot. The combined power will be the sum of each individual laser. The closer each beam is to perpedicular to the target surface, the more focused each beam is. I don't know the answers to the rest of your post, so I can't help you there. Also, you must be VERY VERY careful using lasers. Always wear eye protection and don't play around with them. It is very easy to be blinded or to blind someone else.

    Edit: What I mean is that you don't even need to use mirrors or lenses or anything. Just put them together and adjust them so that they focus on the same spot at a given distance. The downside is that they will ONLY focus on a spot at that distance. A closer or further target will not be in focus.
     
  4. Jul 10, 2011 #3
    i know that can be done but i do not want to focus the beams each-time(for different distances).
    can a solution to this be obtained through basic ray optics of light fot LASER too?
    i mean refraction through a prism, T.I.R etc....
     
  5. Jul 10, 2011 #4

    Drakkith

    User Avatar

    Staff: Mentor

    I would think two lenses, one converging and then followed by a diverging lens would work. But I have absolutely no idea if it will or not. Maybe someone else can help.
     
  6. Jul 11, 2011 #5

    Andy Resnick

    User Avatar
    Science Advisor
    Education Advisor
    2016 Award

    If you want to combine a lot of tiny lasers into one giant laser beam (i.e. coherent addition), you can't, by thermodynamic arguments. If you simply want to dump a lot of power into a small volume using lots of little lasers (incoherent addition), you can (as Drakkith mentioned).
     
  7. Jul 11, 2011 #6
    Well, it's possible (it has been done many times) to add coherently several small laser to get a bigger one. However, it's complex, expensive and the resulting beam isn't as good as the one you get with a single lasr,
    I´m not aware of thermodynamic restrictions to phase-lock lasers in order to get coherent addition.
     
  8. Jul 11, 2011 #7

    Andy Resnick

    User Avatar
    Science Advisor
    Education Advisor
    2016 Award

    The argument is conceptually similar to the (incorrect) idea of taking a randomly polarized field, splitting it into orthogonal polarization states, rotating one, and recombining the two beams into a single polarization state. Etendue (or if you like, beam waist * divergence angle) is a conserved quantity. Yes, it is possible to coherently combine a small number of lasers, but the overall brightness of the combined beam is less than incoherently adding the beams.

    http://www.col.org.cn/abstract.aspx?id=COL07111012-03 [Broken]

    reports an efficiency of 85.3%.

    http://qurope.eu/content/coherent-addition-laser-beams-resonant-passive-optical-cavities [Broken]

    report about 25% efficiency.

    http://authors.library.caltech.edu/7649/1/LIAoe07.pdf

    do not report the output power, but it appears to be < 1% of input.
     
    Last edited by a moderator: May 5, 2017
  9. Jul 11, 2011 #8
    That's different. Combining laser beams, even in a coherent way, is less efficient that a single laser. What I liked to point out was that coherent addition, however inefficient, is possible.
     
  10. Jul 26, 2011 #9
    thank you for your help guys....
     
  11. Jul 27, 2011 #10
    Would shooting a laser through a magnifying glass actually magnify a beam?
     
  12. Jul 27, 2011 #11

    Drakkith

    User Avatar

    Staff: Mentor

    Sure. But the beam doesn't get any stronger, it is only focused more tightly.
     
  13. Aug 4, 2011 #12
    Check out High-Power Fiber Coupled lasers. They are all the rage in industry these days, just take a bunch of VECSELS, couple all the output into fibers and splice the fibers together. They have been around for a while, and are replacing CO2 lasers for industrial cutting/machining services. The US NAVY is actually developing one of these types of lasers to build a really cool ship borne laser gun. http://latimesblogs.latimes.com/technology/2011/04/navy-laser-weapon-fire-.html

    The only problem is the beam quality is not quite as close a Gaussian beam as a gas laser is because the individual diode beams does pixel-ate in a sort of way, but they are reaching well into the kW range.
     
  14. Aug 4, 2011 #13

    Integral

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    If a laser beam passes through a converging lens ( a magnifying glass) it will converge to a spot at the focal length of the lens, this concentrates the lasers power. A 30W laser with a 3mm beam diameter focused to a 30 micron spot will vaporise Si. A powerful laser and a http://www.sino-galvo.com/content/products/galvanometer-scanner-jd1403.html" [Broken]can be used for cutting intricate patterns in a wide variety of materials.

    Of course this is pretty much the end of the laser beam as it diverges on the other side of the spot.
     
    Last edited by a moderator: May 5, 2017
  15. Aug 5, 2011 #14

    Drakkith

    User Avatar

    Staff: Mentor

    More of a laser Dot instead of a Beam then eh?
     
    Last edited by a moderator: May 5, 2017
  16. Aug 5, 2011 #15
    That is still pretty cool, I have a magnifying glass and a broken Playstation, I think you can see what I'm getting at?!
     
    Last edited by a moderator: May 5, 2017
  17. Dec 2, 2013 #16
    I think most of the readers missed the point of this thread however it is very possible and i do it daily at work.
    There are 2 ways to converge lasers into a single coherent beam
    1. if they are of different wavelength then use a dichroic combining system so that one wavelength is your primary ( green usually ) and use a dichro to pass green and reflect blue at 90 degrees to the primary beam .. and so on
    Secondly if you are using the same wavelength the best way is to use a polarising cube as a beam combiner. for example Horizontal waves pass straight through and vertically polarised light reflects from a 90 degree source.. simple
     
  18. Dec 2, 2013 #17
    I do not see why coherence is important here. Assuming the original poster is happy with the performance of a single beam, then having multiple such beams very close to each other and nearly parallel with each other should also be quite acceptable. And that needs only a bunch of mirrors on a sturdy support, and a terrible lot of patience to adjust the thing.
     
  19. Dec 2, 2013 #18
    In posting a greatly belated reply simply adds to the pool accessible of knowledge, regardless of the timeframe.

    What i posted was nothing more than a simple mechanism so that other newcomers can learn from those who actually work with lasers professionally
     
  20. Dec 2, 2013 #19
    Oops. I did not realize the thread was revived from a two years slumber.
     
  21. Oct 6, 2015 #20
    It looks like I am little late to this thread. I believe there may be an easier way to combine laser beams of any wavelength to make a more powerful laser. Here are couple of concepts of adding subsequent lasers at a point of total internal reflection and axially align multiple laser beams.

    Example 1: Wave Guide Approach
    Webb Method Axially Combine Mutiple Lasers.png



    Example 2: Virtuous Circle Approach
    Webb Method Axially Combine Mutiple Lasers_2.png
    The closer to the edge of the denser than air transparent medium the more sides and the more lasers can be added. Now I have some concern that a cylindrical shape on the reflection point may upset the laser; so we can use multi-sided optic to be safe.


    Example 3: Hex My Ex Approach (Any uniform multi-sided shape will do)

    Webb Method Axially Combine Mutiple Lasers_3.png


    I have a few more approaches that I came up with based on a different concept, but results are the same. As you may surmise in these basic examples you can daisy chain these elements together and make a very powerful laser or create a loop to cycle the light to make laser pump to make up for the inefficiencies. The number of lasers that can be added is limited to first laser not adding any additional photons to the output and that will be dependent on the precision of the system.

    Happy Lasing,
    Jeffrey Webb
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Combine lasers to make a single strong beam
  1. Laser Combination (Replies: 14)

Loading...