Can we connect two laser sources to make a stronger beam with a larger radius?

[danHa]

there is anything that have input of two laser and output one laser with a bit bigger radios or just stronger laser like a beam just the opposite instead of splitting one sources connect two sources

 

[Nugatory]

You will have to phrase your question more clearly - “a bit bigger radios” and “do the upside thin” make no sense.

(If you’re using some automatic translation software here... it’s not working)

 

[berkeman]

I'm guessing radios --> radius. I've made that correction to the thread title.

 

[berkeman]

there is anything that have input of two laser and output one laser with a bit bigger radios or just stronger laser like a beam just the opposite instead of splitting one sources connect two sources

Welcome to PhysicsForums.

Assuming that I understand your question, it is more common to amplify a laser beam to make it stronger. Here is a website that describes how they do such beam amplification at the Inertial Confinement Fusion facility in Livermore, California:

https://lasers.llnl.gov/science/icf/how-icf-works

 

[Averagesupernova]

Laser engraving systems I have worked with will use an optical combiner to get more power onto the workpiece. Unfortunately this is about all I know about them.

 

[DaveE]

This kind of depends on how you define what a Laser is. Beams can be combined to travel in the same direction, hit the same target, etc., as in the two previous replies.

However, I wouldn't call these a Laser, it's a combination of separate Lasers. Fundamentally different that splitting a Laser beam in half. The reason is that Lasers aren't just beams of light, like a flashlight. They have a very special property called coherence, which means that all of the photons in the laser bean have exactly the same frequency (color) and are oscillating in the same phase. To achieve this property the photons have to be created in the Laser with the correct frequency and phase, it is essentially impossible to combine them from different sources and get this sort of synchronization later. This isn't a trivial distinction, many of the really useful properties of Lasers depend on this feature.

 

[tech99]

This kind of depends on how you define what a Laser is. Beams can be combined to travel in the same direction, hit the same target, etc., as in the two previous replies.

However, I wouldn't call these a Laser, it's a combination of separate Lasers. Fundamentally different that splitting a Laser beam in half. The reason is that Lasers aren't just beams of light, like a flashlight. They have a very special property called coherence, which means that all of the photons in the laser bean have exactly the same frequency (color) and are oscillating in the same phase. To achieve this property the photons have to be created in the Laser with the correct frequency and phase, it is essentially impossible to combine them from different sources and get this sort of synchronization later. This isn't a trivial distinction, many of the really useful properties of Lasers depend on this feature.

It seems to me that if we place two lasers side by side, then at a great distance, greater than about diameter^2/(2*lambda), the beams will overlap. The spot will be the same size as for one laser, and the two beams, being incoherent, will add on a power basis, so the intensity of the spot will be doubled.
I also suspect that, had the two lasers been coherent, we would see an interference pattern, and the maximum intensity would be four times that of a single laser, because the two fields add rather than the power.

 

[Milsomonk]

Coherent beam combination is very much an active field of research. The idea is to take several laser beams and combine them such that there phase relationship is locked and one gets constructive interference of the EM wave. This is difficult and requires phase modulation at sub-femtosecond timing, but is by no means impossible and has been demonstrated experimentally many times.

There are a few approaches, the first is the tiled aperture approach, one locks the phase of n beams such that they are temporally phase locked but spatially separated, the beams are then incident on a focussing optic. The focussing optic combines the beams and the result is a coherently combined laser beam. There are drawbacks to this method as we obtain side peaks from the focussing optic that can contain a large portion of the optical power. There are some techniques to mitigate this effect to some extent but we always lose some power as a basic fact of Fourier optics.

Another approach is called filled aperture where we can combine beams either using a diffractive optical element or making use of the polarization sensitive optics to split and recombine beams. There are other methods such as spectral beam combining which makes use of the bandwidth of wavelengths in our laser pulse to split and recombine beams. It is also sometimes useful to combine our beams incoherently, where the phase relationship is not locked to produce constructive interference.

To summarize, yes you can make a more powerful laser beam from lots of smaller less powerful beams!

 

[sophiecentaur]

we would see an interference pattern,

Depending on the alignment of the two sources, that pattern could be much finer than the spot size, which may or may not matter. I imagine that the combining system would need to be coaxial for best coherence.

 

[tech99]

If the lasers are side by side, we would see the "double slit" pattern superimposed on the spot. The two patterns multiply in terms of relative field strength. The problem is how to make a coaxial combiner with zero loss. Then the spot would be the same size as for one laser but double the intensity.

 

[sophiecentaur]

The fringes would be very fine for any practical separation and very much affected by the width of the beams. Probably more speckles than straight fringes?

 

[tech99]

Do we get speckles in the far field? Not sure.