the equilibrium particle distribution contrary

Light through the work material, the light energy will only weaken not strengthen.  Laser Pointer  is especially used for computer mostly by the business man. To make the dominant stimulated emission must be made in a high energy level E2, the number of particles is greater than the number of particles in a low energy level E1. This distribution coincided with the equilibrium particle distribution contrary, called population inversion distribution referred to as population inversion. How technically to achieve population inversion is a necessary condition for producing laser. Theoretical studies have shown that the substance of any work, under appropriate excitation conditions, in particular between the high and low level of the particle system inversion. If the microscopic particles such as atoms or molecules with a high energy level E2 and low energy levels E1, E2 and E1 on the level of the population number density of N2 and N1.  Laser Pointer  is well received in America and Europe.
The existence of the spontaneous emission transition between the two energy levels, stimulated emission transitions and the three processes of stimulated absorption transition, etc.. By stimulated emission transitions generated by stimulated emission of light, with the same frequency, phase, direction of propagation and polarization direction with the incident. Therefore, a large number of particles at the same excitation of the coherent radiation field generated by stimulated emission of light is coherent. Monochromatic energy density by the stimulated emission transition probability and the stimulated absorption transition probabilities are proportional to the incident radiation field. When two levels of statistical weight equal to the probability of the two processes are equal. More technical details of Laser Pointer  should be determined as soon as possible.
N2, <N1 in the case of thermal equilibrium, so spontaneous absorption transition dominated by the light through the material, usually due to shock absorption and attenuation. External energy incentives can destroy heat balance N2, leaving> N1, this state is called population inversion state. In this case, the stimulated emission transition dominant. Light passing through a period of length l in the inversion state laser material (active material), light intensity increased eGl times. G is proportional to the coefficient of (N2-N1), known as the gain coefficient, its size and the nature of the laser material and the light wave frequency.