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 Period of activation of the substance is a laser amplifier. If the period of activation of the material placed between two parallel mirrors (at least one part of the transmission) constitute the optical cavity (Figure 1), in the spontaneous emission of particles of high energy level will produce a variety of directions. Pagedown function of Laser Pointer  has been added.
Among them, the non-axial propagation of light waves soon escape the cavity: the axial propagation of light waves can spread in the cavity round-trip, when it is spread in the laser material, the growing intensity. If the resonant cavity one-way small-signal gain G0l greater than one-way loss δ (G0l by the small signal gain coefficient), and may give rise to self-oscillation. The state of motion of the atoms can be divided into different energy levels, when the atomic transition from high energy level to a low energy level, and will release a corresponding energy of the photon (the so-called spontaneous emission). Similarly, when a photon is incident to a level system in and absorb the words, cause the atoms from the low energy level transition to the high energy level (so-called stimulated absorption); then part of the transition to a high energy level atom will transition to a low energy level and the release of photons (so-called stimulated emission).  Laser Pointer  can help the lecturer to display the document better. The factory can provide the normal warranty for Laser Pointer
These movements are not isolated, but often at the same time. When we create a condition, such as the use of the appropriate medium, the cavity enough external electric field by stimulated emission of radiation to be amplified to give than to receive shock absorption to be more, so overall, there will be photon emission, resulting in a laser. Ordinary light is the light-emitting in all directions. Let the light emitted toward the direction of propagation, the need to give the light source fitted with a certain light-gathering device, such as the car's front lights and searchlights to install the condenser the role of mirror so that the radiation light brought together in one direction injection. The design of  Laser Pointer  will be discussed in the meeting.
The laser emission of the laser is inherently injection in one direction, beam divergence is very small, only about 0.001 radians, close to parallel. In 1962, the first human use of laser irradiation the moon, the earth from the distance of the moon is about 380,000 km, but the laser spot on the lunar surface is less than two kilometers.