High-energy laser takes you into the internal structure of the laser
The usual laser is composed of two parts, namely the laser working material, the pump source and the optical resonant cavity. Below we respectively describe the structure and function of these three parts. In order to form a stable laser, there must first be luminous particles capable of inverting the number of particles, which we call activated particles. They can be molecules, atoms or ions. Some of these activated particles can exist independently, while others must be attached to certain materials. The materials that provide storage places for activated particles are called tombs, and they can be solid or liquid. The matrix and the activated particles are collectively referred to as the laser working substance. In order to form the puller number inversion, it is necessary to excite the laser working material, and the pump source is the one that accomplishes this task. Different laser working materials often adopt different pump sources. For example, a solid-state laser generally uses an ordinary light source such as an ammonia lamp as the pump source to illuminate the laser working material, which is also called an optical pump. For gas laser working materials, they are often sealed in a thin glass tube. Voltage is applied to both ends and excited by the method of discharge. Just make the laser working material in the puller number inversion state, although the laser can be obtained, its life is very short, the intensity is not too high, and there are many light wave modes and poor directivity. Such lasers have little practical value. In order to obtain a stable and continuous high-quality laser output with a certain power, the laser must also have an optical resonant cavity. It is composed of two mirrors placed on both sides of the laser working material, one of which is a total reflection mirror, and the other is used as an output mirror, which is a partial reflection and partial transmission half mirror. The role of the optical resonant cavity mainly has the following two aspects. (1) Generate and maintain laser oscillation. The light is amplified when it propagates in the laser working material with the population inversion. Due to the existence of the optical resonant cavity, on the one hand, under the optical positive feedback provided by it, the photon number factor in the cavity is Continuously going back and forth through the laser working material to be amplified; on the other hand, due to various losses in the resonant cavity (such as output loss, diffraction loss, absorption and scattering loss, etc.), the number of photons in the cavity continues to decrease. When the amplification and attenuation cancel each other out, a stable optical oscillation can be formed, and a laser with stable output power can be formed. (2) Improve the quality of output laser. Since the characteristics of the laser beam are inseparably related to the structure of the resonant cavity, the purpose of controlling the characteristics of the beam can be achieved by changing the cavity parameters, such as improving the directionality, monochromaticity, and output power of the laser.