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Multi diode + 1/2 mirror --- how much power loss?

Ashton

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I've asked this on other forums and never gotten a good responce, I'm wangint to take a half-dozen diodes and combine their beams into one high-pwoere laser module. The only trick I've seen for this in a "flashlight" (I want it portable, not a labby with a fixed focal-length from jsut aiming hte alsers together) is to use 1/2 mirrors and keep firing the lasers through.

What kind of loss would I get from this? if I started with (for simplicity's sake) a 100mw diode, how many mw woudl escape? 95? 90? 50? keep in mind I will be stacking these, so the back diode will be passing through atleast 4 if not 6 1/2 mirrors and the first one will simple be reflecting from one.

Any better ideas of how to build a portable hgh-pwoered laser? people talk about beam combiners but nobody ever explained how they work, so I'm in the dark. I thought I could aim all the lasers at one point at the lens and it owuld focus them out in one beam, but I was told this didn't work (just verifying)

My aim is to first build a 1watt laser and eventuallly built a 2watt or more. --- for under $200 ($20 each for 200mw DVD burners, so 5x of those is 1W, 10X is 2W)
 





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Re: Multi diode + 1/2 mirror --- how much power lo

Ashton --

There's a number of us trying to build the "death star" array Nothing so far looks promising within a limited $$$. This is where the science begins !!
We got to try these ideas. mirrors, polarizing beam combiners etc etc....Maybe a big lens.
If we could just buy this stuff -- where's the hobby ??

Mike
 

Ashton

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Re: Multi diode + 1/2 mirror --- how much power lo

well, unfortunately, not everyone can afford to drop $500 for a lasercheck to show how much pwoer is being lost... I figured tehre was a forumla that I could plug my info into and get a rough idea how much power I lsoe with every mirror (After all, if by mirror 6, diode 1 is only pumping out 1mw, the whole point is invalidated!)
 

Rhith

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Re: Multi diode + 1/2 mirror --- how much power lo

I would recommend setting up one laser and have it go through all of the mirrors, as to represent the one in the back, and see how it does once it makes it to the end. Worth a try before you set up a whole row of these! ;D
 

JES

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Re: Multi diode + 1/2 mirror --- how much power lo

I have been thinking about this too and came up with the same problem. I imagine it is a function of the quality of the glass you get but I am betting that the additive effect is going to kill performance.

It seems like the place to make the merge is between the LD and the lens. Here is a collimating lens diagram that is rather nicely done.

w ww.sinopt.com/software1/usrguide54/examples/diodcoll.htm
(take the space out. i'm new and not to be trusted with links)

It would be interesting to see what happened with several LDs and a large collimating lens. You wouldn't get a coherent output--a phased array is a different beast. Would that even matter for the purpose?

Google 'laser diode array' and see that there is a lot of work going on on this topic out there. Those are coherent; they are in phase and identical frequency. I remember seeing how the phased array radars work. They use cables that are slightly longer for different emmitters. The distance that the electricity must go through a longer cable to get to a second emmiter is the difference in the peak and trough of the wavelength of the radar so the emmitters stay 'in phase.' That would be difficult to replicate on a breadboard methinks...
 
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Re: Multi diode + 1/2 mirror --- how much power lo

Jes --

I've done some of that coax cable length stuff with VHF and UHF radio frequency but here I see a problem putting diode output into a lens from a slight angle. It seemed so easy at first :(

Mike
 

JES

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Re: Multi diode + 1/2 mirror --- how much power lo

Hemlock Mike said:
Jes --

I've done some of that coax cable length stuff with VHF and UHF radio frequency but here I see a problem putting diode output into a lens from a slight angle.  It seemed so easy at first  :(

Mike

Yep. The actual emmitters, not the cans would need to be very very close. Perhaps we could shave five of them down and mount them into a pentagon array...who has a steady hand with a dremel?
 
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Re: Multi diode + 1/2 mirror --- how much power lo

Jes -- That's about what I was planning but still the center line of diode output would be off the center axis of the lens.
I'm still working on this as time allows. "The Death Star Project" !!! Many have tried.

Mike
 

Benm

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Re: Multi diode + 1/2 mirror --- how much power lo

I remember seeing how the phased array radars work. They use cables that are slightly longer for different emmitters. The distance that the electricity must go through a longer cable to get to a second emmiter is the difference in the peak and trough of the wavelength of the radar so the emmitters stay 'in phase.'

Such technologies will not work for (homebew) optical devices. It requires cutting cables to different lengths with a precision much better than the wavelength of the signal. At a few 100 MHz this is no problem, as a wavelength is still 1 metre (at 300 MHz), and you can cut coax cable with milimitetre precision by hand.

Translated to the optics required for visible lasers, this would mean machining parts with a precision of 10 nm or so. This is doable in lithography (making chips), but not my any mechanical means.
 

Aseras

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Re: Multi diode + 1/2 mirror --- how much power lo

the only way to combine more than 2 beams is to use polarizing cube beam splitter(s) ( dvd burners have small ones that's the cheapest place you will find them )

M=mirror
b=polarizing beam splitter
)=focusing lense
L=laser module it should already be colliminated and focused.

/-----------------------)------------------
M b b b b lense
| | | | |
[] [] [] [] []
L L L L L

it's very complicated. you start with one aim, shut it down alingn the next one to match the aim of the first and reapet down the line. then when you fire them all up you should have a combined beam. You can turn any of them off at random to make any color combination you want.

Another worry is that the beam splitter only work for certain wavelengths. they reflect one and transmit another, so you have to use certain ones in order to get it to carry the combined beam and not reflect it.
 




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