[dleviwing]

Originally Posted by AntonioLao

for LASER, it's just the opposite: photons attract each other.

Antonio;
The photon is a quantity (Quantum) of energy absorbed or emitted by matter. It is not a traveling particle of light unless you are considering it as a piece of the wave. The waves from a laser are coherently aligned waves. This means that diffraction is minimized due to the alignment of the electric and magnetic vectors. (polarized light) The waves do not repel or attract. They do however have interference.
Particle physicists like to think in terms of particles for everything. It makes the math work better.