People should purchase a green laser pointer with good anti-interference property

The coherent photons within the volume of degeneracy four kinds of meaning: the four-photon degeneracy of the meaning of the photon number, in the same relative number of photons inside. (2) spontaneous emission: emitted by the atomic spontaneous transition phenomenon of light. Spontaneous emission: spontaneous emission (3) stimulated absorption transition: in the low-energy state E1 of an atom at a frequency of ν role of the radiation field (excitation), the stimulated absorption transitions: stimulated absorption transition energy of photons absorbed to a certain energy state E2 transition process. (4) stimulated emission and stimulated emission transitions: stimulated absorption of the anti-transition process is stimulated emission transition. The latest green laser pointer can remote control the computer and write letters on the wall as well.Can be stimulated in the stimulated emission of radiation and transitions: stimulated emission and stimulated emission class E2 transition frequency v of the atoms in the radiation field, the transition to a low-energy state E1 and radiation photon energy hv. Stimulated radiative transition into light waves emitted by the stimulated emission. (5) inversion: in the non-thermal equilibrium, energy level is greater than the population on low-level set of populations, known as the population on the anti-inversion: the number of anti-particles around (inversion). (6) self-oscillation conditions: small signal gain coefficient g0 loss greater than or equal to include amplifiers and cavity loss in the self-excited oscillation conditions: self-oscillation conditions the average loss factor α (7) The main characteristics of the led flash light: spatial coherence and direction, temporal coherence and monochromaticity, high brightness (strong coherent laser main features: the main characteristics of laser light) 3.To choose a perfect green laser pointer people should firstly check out by its appearance. In order to make helium-neon laser coherence length of 1KM, it should be the number of monochromatic ? Solution: Let the coherence time τ, then the coherence length of the speed of light and the coherence time of the product, that if the laser and maser at 10? M, 500nm and output power of 1 watt continuous, asked on the second level from the laser level down is the number of particle transitions? solution: power is the energy output per unit time, so we set out in the time dt the energy dE, then power = dE / dt laser or maser output electromagnetic energy is the Planck constant and the product, that is: dE = nhν, dt where n is the number of photons within the output, which is equivalent to the cavity photon number of excited particles in high energy radiation in the time dt transitions to low-level number (frequency between energy levels ν). The above analysis can be the following form: To determine the molecular energy levels of the spontaneous emission lifetime E4 τs4. People should choose a green laser pointer by well knowing its practical functions.Continuous excitation in the E4 and reached steady state, find the corresponding ratio of the number of particles on the energy level and state level at this time between the two in which to achieve a set of populations. Solution: (1) the meaning of the questions we can see the low-energy particles on the E4 level A4 for the spontaneous transition probabilities: the molecular level of the spontaneous emission lifetime E4: Conclusion:People should purchase a green laser pointer with good anti-interference property. If the transition to the next level u occur more than one level, can u i-th level to which the probability of spontaneous transition energy levels for the Aui is the spontaneous emission lifetime of u: (The physical meaning of the above three equations are: spontaneous emission only consider the high energy level and energy level E1 and E4 level only between stimulated absorption process, see Figure) macro-level performance for the number of particles does not change, and further can be obtained.