This is incorrect. Laser beams are only "straight" at short range. At long range, laser beam intensity does decrease as 1/r^2. The reason for that is that the d

This is incorrect. Laser beams are only "straight" at short range. At long range, laser beam intensity does decrease as 1/r^2. The reason for that is that the diameter of the laser beam increases due to diffraction. If you want to know why, I recommend reading about Gaussian beams and Rayleigh Range.