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Laser Harp

T

timelord

Guest
I'd recommend a laser with 100% duty cycle, as for that the dragon it is only good for 60 seconds up. So maybe a Lucent envee 100mw could do this as they are the cheapest 100% duty cycle laser about for only $295 + $5 shipping. ;)
 





K

kenrok1

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Feb 12, 2007
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I have never experimented with any of this so don't take my comments to have any authority, but I don't think beam splitters are any less efficient than diffraction grating... it's just how that loss is distributed.

Like pseudo said about a diffraction grating having a greater concentration at source with the output diminishing as the beams progressed, whereas an array of 1-into-2 beam splitters could net uniform results. Something like this:


(poor, non-scientific illustration shown w/100mw source as example)



12.5 12.5
| 100mw |
12.5-[] | []-12.5
|25 50 | 50 25|
[]---------[]---------[]
|25 25|
12.5-[] []-12.5
| |
12.5 12.5



vs the diffraction grating:

100mw
6.25 12.5 25 50 | 50 25 12.5 6.25
\ \ \ \ | / / / /
 
P

pseudonomen137

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Niks, I think you're a little confused about diffraction gratings. Beam splitters will split the beam up into weaker beams, yes, but so do diffraction gratings. A 100mW laser through a diffraction grating will not create many 100mW beams, that would be even better than perpetual motion! Unfortunately you can't pull power out of thin air so easily. Using a series of beamsplitters will make each individual beam weaker, but no worse than a diffraction grating. I think using a diffraction grating would lead to a worse overall loss of power (as some beams would have to be blocked out, unlike with beamsplitters), though it would be a far simpler solution. Either way, if you have X beams from a Y power laser, each beam will be no stronger than Y/X, period, and in all likelihood will be a good amount less than Y/X (EDIT: Well, I guess that technically only applies if all beams are equal power, but still, you can't end up with more enegry out than you put in).

I think you're also underestimating power. 100mW laser becoming undetectable after beamsplitters? Even 5mW is an awesome amount of power and we normally take it for granted. A photodetector would easily pick up a few microwatts or less. The only concern would be lesser visibility to an audience (in this case, even 100mW is weak), but a diffraction grating far from solves the problem. Unfortunately, the only solution in that case is good old fashion money. The more you want, the more you'll be paying. To make a visible harp for outdoor audiences like I believe the Jarre guy uses, even the most expensive Hercules laser would fall far short.
 
N

Niks

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Mar 1, 2007
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Hey guys, thanks a lot of ur input on all this. I understand this whole beam splitter and diffraction grafting a lot more better now through reading your comments and also doing some fair bit of research online.

I guess the only way I could do this successfully without having to deal with any losses is using 12 small green laser diodes? How much power will I need per diode and does anyone know where I can get any from? I guess from this I will need to supply power to each individual diode, am I right?

Niks
 
S

SenKat

Guest
Well, according to the Wiki article - you will need 20mw minimum for each beam....You may be able to tie them all together in the same power supply, but it would have to be a rock solid unit.....You are most likely talking about multiple thousands of dollars to do this project, I would think....
 
P

pseudonomen137

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Unfortunately there are no such thing as viable green laser diodes yet. You need to buy the full DPSS 532nm greenies. To get ones without duty cycle in those >20mW powers SenKat mentioned, it would be pretty dang expensive for 12 of them. 12 weak aries would still run you into the $2k range. At that price you could get a 1 Watt lab module almost. Its probably still best to buy a module and split up the beam, but you'll be needing some serious money either way to get 12 20mW beams (minimum of 240mW 532nm power will cost you a few hundred regardless of how you approach it.)
 
R

Ragnarok

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Nov 10, 2006
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I think that individual low-power lasers would be much easier to work with than one large laser with an optical array. I note that Aixiz currently sells a 10mW green module for US$75, and 30mW green modules for US$115. Twelve 30mW modules would total US$1380 (maybe less if you ask them about a volume discount?), eliminate the added expense of optics and uneven beam power, and each module's beam can be positioned where you want it to go, independently of the others.

A 300mW laser is close to US$1000, and the parts and construction of an optical array to convert that into twelve beams of similar power, geometrically arrayed as desired, is going to be much more expensive than individual lasers, not to mention fragile.

Just my 2 cents worth.
 
S

stevetexas

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