Combine lasers to make a single strong beam

[dragonarm]

hey i am a total newbie and a beginner in science well i want to know if the following can be done:-
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?
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...

 

[Drakkith]

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.

 

[dragonarm]

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...

 

[Drakkith]

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.

 

[Andy Resnick]

hey i am a total newbie and a beginner in science well i want to know if the following can be done:-
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?
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...

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).

 

[Gordianus]

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.

 

[Andy Resnick]

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.

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

reports an efficiency of 85.3%.

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

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.

 

[Gordianus]

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.

 

[dragonarm]

thank you for your help guys...

 

[Darrenmackenz]

Would shooting a laser through a magnifying glass actually magnify a beam?

 

[Drakkith]

Would shooting a laser through a magnifying glass actually magnify a beam?

Sure. But the beam doesn't get any stronger, it is only focused more tightly.

 

[jonthebaptist]

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.

 

[Integral]

Would shooting a laser through a magnifying glass actually magnify a beam?

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" 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.

 

[Drakkith]

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" 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.

More of a laser Dot instead of a Beam then eh?

 

[Darrenmackenz]

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" 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.

That is still pretty cool, I have a magnifying glass and a broken Playstation, I think you can see what I'm getting at?!

 

[gsuter]

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

 

[voko]

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.

 

[gsuter]

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

 

[voko]

Oops. I did not realize the thread was revived from a two years slumber.

 

[jeffwebb]

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

Example 2: Virtuous Circle Approach

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)

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

 

[CircuitBurner]

There ARE phase considerations to be had.
Combining many into one does work, and with little losses if implemented correctly.
Heres where it gets complicated.
Even with correct optics for beam combining, if the frequency of each beam added isn't phased properly, its beam becomes a subtractive element, not an addition. This phasing is a function of matching the freqencies of each beam added and then controlling each beam frequency at the wave level to syncronize the beams waveforms. Out of sync is loss, regardless of optics. This phase control of each laser element becomes pretty complex as you add elements. But alas, to the garage inventor who only wants to combine two or three beams... there is hope.
Given that youve already made the investment of time and $$ to get your combining optics set up good, the phasing doesn't have to be prohibitive...just build a driver circuit for your laser elements that features a variable pot to shift the frequency a little, (all laser diodes can vary their output frequencies by slight voltage and amperage changes) , and another pot to shift start phase a little (small variable delay in the start of diode)... then you could just tweak the adjustments with a screwdriver until your combined output peaks. adding many more elements makes this exponentially more complex with each added element. Two would be easy, Three or four would be tedious, Five would have you puling your hair out...and so on...

 

[rxyzm]

There ARE phase considerations to be had.
Combining many into one does work, and with little losses if implemented correctly.
Heres where it gets complicated.
Even with correct optics for beam combining, if the frequency of each beam added isn't phased properly, its beam becomes a subtractive element, not an addition. This phasing is a function of matching the freqencies of each beam added and then controlling each beam frequency at the wave level to syncronize the beams waveforms. Out of sync is loss, regardless of optics. This phase control of each laser element becomes pretty complex as you add elements. But alas, to the garage inventor who only wants to combine two or three beams... there is hope.
Given that youve already made the investment of time and $$ to get your combining optics set up good, the phasing doesn't have to be prohibitive...just build a driver circuit for your laser elements that features a variable pot to shift the frequency a little, (all laser diodes can vary their output frequencies by slight voltage and amperage changes) , and another pot to shift start phase a little (small variable delay in the start of diode)... then you could just tweak the adjustments with a screwdriver until your combined output peaks. adding many more elements makes this exponentially more complex with each added element. Two would be easy, Three or four would be tedious, Five would have you puling your hair out...and so on...

I am a newbie here.

After going through this thread,

I was just wondering, whether a Concave Mirror can be used as a beam focusing device to a single point/beam at "F" of Mirror; for multiple small powered parallel laser beams pointing at the mirror from a point just outside of F?

Warm Regards,

Ravi