the injection of the laser beam

In this case, the stimulated emission transition dominant. Light through a period of length l in the inversion state of the laser working substance (active substance), the light intensity increases eGl times. G is proportional to the (N2-N1) of the coefficient, called the gain factor, and its size is also working with the nature of the material and the laser light frequency. Period of active material is a laser amplifier. If, for some active substances on the two mirrors parallel to each other (at least one of which is part of the transmission's) constitute the optical resonator (Figure 1), at high energy particles will produce a variety of directions of the spontaneous emission. Among them, the non-axial propagation of light waves outside the cavity escapes soon: axial propagation of light waves able to spread in the cavity round-trip, when it spread in the laser material, the light intensity is growing. If the resonant cavity G0l small-signal gain is greater than one-way one-way loss δ (G0l is the small signal gain coefficient), can generate self-excited oscillation. The freeing shipping can be supplied for the large quantity order of  laser pointer .
State of motion of atoms can be divided into different levels, from high energy level when the atomic transition to the low level, it will release the corresponding photon energy (the so-called spontaneous emission). Similarly, when a photon incident on a level system, and work to absorb it, will lead from the low-level atomic transition to the high energy level (so-called stimulated absorption); then, part of the transition to high-level atomic transition to the low level will and release a photon (the so-called stimulated emission). These movements are not isolated, but often simultaneously. When we create a condition, such as the use of appropriate media, cavity, enough external electric field is amplified by stimulated emission of radiation to be more than the stimulated absorption, so overall, there will be photon emission, resulting in the laser. The infrared  laser pointer  acts well in performance. The advantage of the infrared laser pointer is the low price. The low price is one of the more remarkable features of  laser pointer . Phenomenon: the injection of the laser beam, like a piece of paper in the spot is not round or exposure is not clear. Output mirror M1, M2 total reflection mirror cavity consisting of run away. First press the power box on the button automatically launches the laser, the frequency of the laser shot per second; and paper in one hand like a perforation at one hand and gently repeated four pitch adjustment screws on the cavity until the launch of The laser beam hit the paper sounded like a strong, spot becomes round and clear. Phenomenon: the injection of the laser beam hit the paper could not see anything like that exclusion method using a regulation does not work.