On the spot, if you hit directly on the surface of an object, you can see a circle around the spot in concentric (or eccentric) interference fringes, conditional friend can try. Power, light and laser wavelength, a relationship model, if the power is low, the military laser model and difference the interference fringes, may not be able to see, in addition to the object showed diffuse severe, may be the main question pattern.
Mainly because the military laser in the rough surface (smooth surface or so-called relative light wavelength is rough… ) diffuse reflection beam at the direction of the eyes, which interfere with each other, forming the particles. In addition to dust, air flow, temperature difference caused by optical path in to occur subtle changes, so these particles are constantly shaking.
Longitudinal mode refers to the form of military laser standing wave resonator is not formed in the same cavity! There will be a lot of wave forms, because meet cavity phase matching condition has a lot of, as long as the conditions can form a stable standing wave meet, a standing wave type corresponds to a longitudinal mode!
Transverse mode refers to the military laser field (including electric field and magnetic field) distribution in the cross section perpendicular to the laser propagation direction on the simple understanding of the field in the face of what! For example the base mode and its distribution in the cross section is a spot, there are a number of high order modes the spot in the cross section!