The incentive process is a necessary condition for optical amplification. Excitation energy with the laser material, solid-state lasers is the use of optical excitation, and gas lasers use of the discharge excitation, the semiconductor laser to inject large current incentives, as well as chemical incentive electron beam excitation, the nuclear incentives. In fact, the laser energy by the excitation energy conversion derived. Laser oscillation. Activation substances in the event of stimulated emission in the same direction will have the same vibration frequency, the chain reaction in the same phase and the polarization properties of light waves, so that the light waves to be amplified. (4-6) in the active material, the distance light waves through the longer, the light waves have strengthened. Set of two mirrors face to face in the activation of the material at both ends. If the customer wants to use green laser pointer .
So that the light waves reflected back and forth to the formation of the feedback amplification, such a device called a laser oscillator, shown in Figure 4-4. Of two mirror resonator. Set to activate the material refractive index in the cavity standing wave wavelengths of light and the length of the resonator. Workers should meet. Where is an integer. Commonly referred to this standing wave longitudinal optical resonator natural oscillation or optical cavity mode, and press analyze. So that the speed of light in vacuum, by definition, can be written as the medium speed of light. Thus, the natural oscillation of the resonator in the frequency of light is equally spaced with the cavity growth, the vertical and horizontal spectral variable density. According to the resonance principle, when the stimulated emission light wave frequency and the natural frequency of the optical cavity phase, the light waves to the optical resonant cavity is amplified, which can be through the optical cavity length and adjust to solve. If the customer doesn’t want others to use green laser pointer .
The reflective surface of the cavity is spherical or flat, which is a completely reflecting surface, another part of the transmission should be able to. When the light round-trip propagation with the optical axis of the deflection of light escaping the cavity, into loss, only parallel to the optical axis of light in order to chain through repeated reflection amplify. Once you gain more than loss of the formation of laser oscillation, and part of the transmission-side output of the resonator and the laser stimulated emission of radiation with the phase shown in Figure 4-5. In summary, the laser forming process as follows: substance so that work by stimulating energy into the active material, the active material to produce a large number of photons of the same characteristics stimulated emission, the stimulated emission maintained through the cavity, stimulated amplification continue to strengthen continuous emission of a large number of photons of the same characteristics, the formation of the laser. Therefore, others can not use green laser pointer .
Clearly, the laser is subject to the results of stimulated emission and resonant cavity together. Clearly, the existence of metastable laser generated a necessary condition. Laser characteristics. Compared with ordinary light, the laser characteristics are as follows. Good direction. Resonator so that only the propagation of light along the optical axis can be repeated reflection is amplified, it can spread along the optical axis, the divergence angle is very small beam. The laser beam divergence angle of only 2 to 3 minutes, and a He-Ne laser at a distance of 20 km, the spot is only 10 cm in diameter. Therefore, the laser can be seen as parallel light. High brightness. The directionality of the laser, using some special technology to make the instantaneous release of energy to activate the accumulation of material over an extended period. It is the electronic assistant of laser pointer .
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