Laser image shape/cross section

[cmcrae1019]

Hi everyone! New here and new to lasers but I have been reading the site over the past week or so trying to educate myself.

My question is about the shape of the laser on the cast on the wall. If the beam is collimated it's going to be a small circle on the wall and using lensing I could defocus that beam to be a larger circle on the wall at the same distance.

Is it possible to create other shapes without losing any energy density? To me the obvious solution would be to block out the parts of the circle that don't fit the desired shape but is it possible to focus the beam into say a star or a square without losing any of that energy density?

 

[Cyparagon]

Is it possible to create other shapes without losing any energy density?

You can increase energy density by leaving the laser on longer. Maybe you mean power density? Power and energy are quite different.

Power density wouldn't make sense either, because all alterations to the beam profile will change power density. Maybe you mean power? Power and power density are quire different.

Power wouldn't really make sense either. No optic is 100% efficient (except maybe a window at Brewster's angle.)

Maybe we'll just get rid of that caveat all-together. Yes, there are optics that change the beam projection from a dot to something else without masking a portion of the beam. Diffraction gratings and cylinder lenses are the most common.