How much would a laser spread out in space?

In summary, the conversation discussed the spread of lasers in space and the precision and accuracy of laser apparatus. It was mentioned that assuming a perfect laser, the far-field divergence is given by a specific equation. However, since even a perfect laser is not possible, the divergence will always be larger. Another way of measuring the spread of a laser is through diffraction effects and using the Rayleigh criterion. The conversation also referenced the use of lasers to range the Moon and the retro-reflectors at Apollo sites and on the Lunokhod rover.
  • #1
Albertgauss
Gold Member
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Hi all,

Does anyone know of any references on how much a laser would spread out in space? I'm not sure if this is the right place for this, but I know there are various experiments planned in the future for space that rely on lasers going back and forth between satellites. Just looking for ball park numbers.
 
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  • #2
That all depends on how precise and accurate the apparatus is. Assuming it is perfect, which it isn't, it never would. I don't really have numbers for you though.
 
  • #3
samblohm said:
Assuming it is perfect, which it isn't, it never would.
Assuming it is perfect, it would diverge as a Gaussian beam. The far-field divergence is given by
[tex]\theta \simeq \frac{\lambda}{\pi w_0}[/tex]where λ is the wavelength and w0 is the waist radius. Even a laser isn't perfect, so the divergence is always more than that for a Gaussian beam.
 
  • #4
One way of looking at it would be through the diffraction effects from passing the beam through a circular aperture, using the Rayleigh criterion.

Once you find out where the first minima occurs you can find how wide that beam is at any given distance by multiplying the angle by the distance to the target, assuming small angles. You can have a play around with the numbers with this app.
http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/cirapp.html
 
  • #5
Research the lasers used to 'range' the Moon via the retro-reflectors at Apollo sites and on Lunokhod (sp) rover ??
 

Related to How much would a laser spread out in space?

1. How does the distance affect the spread of a laser in space?

As distance increases, the spread of a laser also increases. This is due to the phenomenon known as beam divergence, where the laser beam expands as it travels through space. The amount of divergence depends on the power and wavelength of the laser, but it is always present to some degree.

2. Can a laser spread out infinitely in space?

No, a laser cannot spread out infinitely in space. Eventually, the beam will become too weak to detect, but it will still continue to spread. Additionally, as the beam travels through space, it may encounter obstacles such as dust particles or gas molecules that can scatter the beam and cause it to spread out even more.

3. How much does the wavelength of a laser affect its spread in space?

The wavelength of a laser can have a significant impact on its spread in space. Generally, shorter wavelength lasers (such as ultraviolet) will have a smaller spread than longer wavelength lasers (such as infrared). This is because shorter wavelengths have higher frequencies and therefore more energy, making them less susceptible to beam divergence.

4. Does the shape of a laser beam affect its spread in space?

Yes, the shape of a laser beam can affect its spread in space. A laser beam with a narrower width will typically have a smaller spread than a beam with a wider width. This is because the wider beam has a larger surface area for beam divergence to occur, while the narrower beam has a smaller surface area and is therefore more focused.

5. Is there a way to minimize the spread of a laser in space?

Yes, there are ways to minimize the spread of a laser in space. One method is to use a laser with a shorter wavelength, as mentioned earlier. Another method is to use beam shaping techniques, such as using lenses or mirrors, to control the direction and focus of the laser beam. Additionally, keeping the laser beam as narrow as possible can also help minimize its spread in space.

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