will fatter beam change beam throw distance?

[planters]

Blue,

so I guess only improving divergence without increasing power and/or beam diameter won't be a solution for getting longer visibility distance.

That is not true.

There are a number of ways to "get longer visibility distance". Each factor contributes. Some factors are more important, but none of these factors undermines the value of another factor. Read that again.

Now, this is not an all inclusive list, but it covers the main factors.
1. Power.
2. Intensity = power per beam cross sectional area as in watts/cm^2
3. Divergence, the lower the better
4. Wavelength. The longer the wavelength the lower the scatter and the lower the power decrease with distance.
5. Pulsed. Within certain limits, and at the same AVERAGE power (joules/second), a pulsed beam will look brighter.

[blue]

I meant only improving divergence might still not be enough unless in a vacuum. In other words I agree with you.

4. Wavelength. The longer the wavelength the lower the scatter and the lower the power decrease with distance.

Thanks for pointing this out! I had this in my mind a while ago but completely forgot about it.
So i guess 445 nm blue appears less bright than same power 532nm green, but at the same time it also helps with visibility distance as the blue photons travel a shorter "path" so have less obstacles on their way?

[norty303]

Divergence and beam diameter/area are intrinsically linked however.
So by improving (reducing) divergence, you have to increase the diameter, which reduces the power density at the source. So whilst you may improve the long range characteristics, you reduce the short range.
There will be a range at which both setups (small diameter/larger divergence or larger diameter/lower divergence) are equal.

[Nii]

5. Pulsed. Within certain limits, and at the same AVERAGE power (joules/second), a pulsed beam will look brighter.

Sorry for bumping an old thread but I'd like to know whether I'm right on this, aside from safety issues with pulsed beams optics have far less damage threshold with pulsed beams, correct?

[buffo]

Correct. If you have two beams - one pulsed and one CW - and they are both rated for an average power of 1 watt, the pulsed laser will have a higher peak power. (Obviously, since it is off for part of the time, when it is on the power level must be higher to obtain the same average power.) If the peak power per pulse exceeds what the optics can handle, then you will damage the coating.

Adam

[VDX]

... I had this with scanner mirrors and a fiber-laser, that can be run in CW-mode and pulsed too.

While the mirrors were OK for up to 50 Watts@1070nm CW in a beam of 3mm diameter, they crack with a 'pulsed' beam from the same laser with 6mm diameter and some 4Watts averaged power ... the "peak power" should then be something like 1kW or slightly more ...

Viktor

[Nii]

I see. Then I guess even if somewhere where pulsed beams for a laser "show" is legal and all safety precautions are taken it's still impractical to use lasers in pulsed mode rather than just increasing the power for CW mode.
Unless a Watt or two in pulsed mode is an order of magnitude brighter to the eye (since the optics I've checked mentioned that they can handle order of magnitude less pulsed beam per cm2 than CW)

Still curious why pulsed lasers were used in a 2008 event in Moscow that blinded so many people http://www.laserist.org/2008-07_russian-incident.htm
Whether it was really worth it to shoot a pulsed beam to the sky as originally planned or the technicians had no idea what they were doing.

[VDX]

... could be, they simply misinterpreted the averaged power of a pulsed laser as equal to the same stated power of a CW-module?

For engraving with blue 3W/6W-diodes and 9W/25W-IR-diodes I'm 'pulsing' them too, but here it's simply high speed modulating the current, so the pulse- or peak power is the same as with CW, only the averaged power per time changes ...

Viktor

[Nii]

These were the same people that decided to point the beams at the crowd rather than the sky as initially planned so I wouldn't be surprised.

But maybe pulsed beam in the visible range appears much brighter to the naked eye than CW. Then it would be understandable.
EDIT:

5. Pulsed. Within certain limits, and at the same AVERAGE power (joules/second), a pulsed beam will look brighter.

The question then is, how much brighter is it that they bothered.

[planters]

But maybe pulsed beam in the visible range appears much brighter to the naked eye than CW. Then it would be understandable.

A pulsed beam will look brighter only if the on/off ratio is low enough that the beam appears pulsed as with a strobe light vs a CW source. If the pulsing is so rapid that it appears continuous then the persistence to the eye will spread the light pulse across the intervening dark periods. It will look continuous and of the same brightness.