Why is green laser light (or its reflection) will look grainy?

When the teacher asked the question of laser principle, the teacher praised me to observe carefully, then tell me this is the green laser light speckle interference phenomenon, because of the special high coherence laser. Gauss beam just shows a cross-section of the laser light intensity on the part of Gauss branch, and the scattered Never mind spot.

green laser light1

The particle state was named “green laser light“. The intensity of speckle pattern is random, can be generated by laser in rough surface reflection or laser through inhomogeneous media. Because most of the surface is rough on the wavelength of light, due to the high coherence laser, when light reflected from the surface of the object. Each point on the object to the appropriate distance of observation point vibration is coherent.

green laser light2

Green laser light is due to photons of frequency, phase and amplitude are the same, each encounter can interfere. Due to surface roughness, a beam of photons in the laser will be rough surface reflection to run around, so it encounters the same phase of the photon, the meeting place will brighten, meet the photon anti phase the place is dark.

green laser light3

The “green laser light” I was not very strict, but the expression of “a small light” laser beam inside the light. In the process of communication, the initial phase (shaking position start) is the same, but the instantaneous phase (the current position of the vibration transmission (with) go forward the process of continuous) to 2 pi (a circle) and the cycle of change.