Metal laser cutting machine is a new type of cutting equipment widely used in industrial production. It gradually eliminates traditional machine tool cutting. Laser cutter is composed of laser cutting machine, cutting head and other components. One of the conventional lasers includes three parts: Working substance, pump source and optical resonator. Let’s go into detail below.
Working Substances
The working substance is the material basis for laser generation, the core part of the laser, and the material system used to achieve particle number inversion and generate stimulated radiation. There are usually two ways to classify the working substances: one is based on the existence form of the working substances, and the other substances can be divided into gases, homogenous bodies, liquids and semiconductors, etc.; the other is to analyze the process of generating laser light according to the rate equation theory. The applicable energy level structure can be divided into three-level system, four-level system and so on.
The particles that generate the laser light in a gas laser are gas molecules or atoms. In solid-state lasers, crystals or glass doped with a small amount of transition metal ions or rare earth ions are used as working substances, and doped ions are used as working particles. and glass as the matrix material. The working substance of a liquid laser is a liquid, and the common one is a dye laser. The working substance is a solution composed of a dye dissolved in a solvent, the dye molecules are working particles, and the solvent is equivalent to the matrix.The working material of semiconductor lasers is semiconductors. Although the semiconductors are solids, the formation mechanism of the population inversion of semiconductor lasers is essentially different from that of ordinary solid-state lasers, so the two are generally not classified into one category.
Pump Source
A pump source (excitation source) is a device that provides energy for population inversion. According to the energy form used in excitation, the pumping methods include discharge excitation, optical excitation, thermal energy excitation, chemical energy excitation and nuclear energy excitation.
Gas discharge excitation is a commonly used excitation method for gas lasers. Its excitation mechanism is to use the ionization and conduction of gas molecules under high voltage. After the electron energy transitions to a high energy level, a population inversion is formed; in addition, the high-speed electrons generated by the electron gun can also be used to pump the working substance to make the transition to a high energy level, which is called electron beam excitation; semiconductor laser clamps the current Achieving pumping is called injection pumping.
Photoexcitation is the use of light to irradiate a working substance, and the working substance absorbs light energy to generate a population inversion. The light source of light excitation can be a high-efficiency, high-intensity light-emitting lamp, and solar energy can be turned into a laser. Solid lasers and liquid lasers commonly use optical excitation methods.
Thermal excitation is to use high temperature heating to increase the number of gas particles on the high energy level, and then suddenly reduce the gas temperature, because the thermal relaxation time of high and low energy levels is different, the relaxation time of low energy levels is short, and the relaxation time of high energy levels is long, so as to achieve high and low energy levels. Population inversion between energy levels.
The chemical energy incentive utilizes the chemical energy released during the chemical reaction to pump the particles to the upper energy level, establishing a population inversion. Unlike the above-mentioned discharge excitation, optical excitation and thermal excitation, chemical excitation requires external energy, so in some special places where there is no power supply, chemical lasers use their specialties.
Optical Resonator
Optical resonator (referred to as optical cavity) is the external condition for laser generation and is an important part of laser. The simplest optical resonator consists of two mirrors coated with a highly reflective material appropriately placed at both ends of the active medium. The characteristics of high directivity, high monochromaticity, high coherence and high brightness of lasers are inseparable from optical resonators. Optical resonators have dual functions of positive feedback and mode selection. The so-called positive feedback, that is, the initial light intensity is called round-trip propagation in the mirror, which is equivalent to increasing the length of the active medium, and finally a certain light intensity can be guaranteed. The so-called mode selection is to control the characteristics of the oscillating beam in the cavity, so that the oscillation established in the cavity is confined to a few eigenmodes determined by the cavity, thereby increasing the number of photons in a single mode, and obtaining good monochromaticity and directivity. Good strong coherent light.