A conventional fiber laser cutting machine laser consists of three parts: the working substance, the pump source and the optical resonator.

1. Working substance Working substance is the material basis for producing laser, is the core part of laser, is used to achieve particle number inversion and produce stimulated radiation of the material system. There are usually two kinds of classification of working substances: one is according to the existence of the working substance classification, working substances can be divided into gas, solid, liquid and semiconductor; The other is to analyze the energy level structure of the laser generation process according to the rate equation theory, which can be divided into three level system and four level system.

In the gas laser to produce fiber laser cutting machine laser particles for gas molecules or atoms, in the solid laser, doped with a small amount of transition metal ions or rare earth ions of the crystal or glass for the working substance, doped ions for the working particles, pumped by the external energy to produce particle number inversion can produce stimulated radiation, crystals and glass for the matrix material.

The working substance of the liquid laser exists in the form of a liquid, a common dye laser, the working substance is a solution composed of the dye dissolved in the solvent, the dye molecule is the working particle, the solvent is equivalent to the matrix. The working substance of a semiconductor laser is a semiconductor, although the semiconductor is a solid, but because the formation mechanism of the particle number inversion of the semiconductor laser is fundamentally different from that of the ordinary solid laser, the two are generally not classified as a class.

2. The pump source is a device that provides energy for the realization of particle population inversion. According to the energy form used in the excitation, the pumping mode has discharge excitation, light excitation, thermal excitation, chemical energy excitation and so on.

Gas discharge excitation is a kind of excitation method commonly used in gas lasers. Its excitation mechanism is that under high voltage, gas molecules ionize and conduct electricity. At the same time, gas molecules (or atoms, ions) collide with electrons accelerated by electric field, absorb electron energy, and then transition to high energy level, forming a particle population reversal. In addition, the high-speed electrons produced by the electron gun can be used to pump the working substance and make it jump to a high energy level, which is called electron beam excitation. Semiconductor lasers are pumped by injecting current, which is called injection pumping.

Light excitation is the use of light to irradiate the working substance, and the working substance of the fiber laser cutting machine produces a particle number reversal after absorbing light energy. Light-stimulated light sources can be high-efficiency, high-intensity luminescent lamps, solar or laser. Optical excitation methods are commonly used in solid lasers and liquid lasers.

Thermal excitation is the method of heating at high temperature to increase the number of gas particles at high energy levels, 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 realize the particle number inversion between high and low energy levels.

The chemical energy excitation uses the chemical energy released during the chemical reaction to pump the particles to the upper energy level and establish the particle population inversion. Unlike the aforementioned discharge excitation, light excitation and thermal excitation, external energy is needed at work, so in some special places where there is a lack of power, chemical lasers can play their fiber laser cutting machine advantages.

3. Optical resonator Optical resonator (referred to as optical cavity) is the external condition of laser generation, is an important part of the laser. The simplest optical resonator consists of two mirrors plated with a highly reflective material placed at both ends of the active medium. The laser has the characteristics of high directivity, high monochromism, high coherence and high brightness, and the fiber laser cutting machine is inseparable from the optical resonator.

Optical resonators have dual functions of positive feedback and mode selection. The so-called positive feedback, that is, the initial light intensity propagates back and forth between the mirrors, which is equivalent to increasing the length of the active medium, and ultimately can ensure that a certain size of the light intensity is obtained. The so-called mode selection, that is, the characteristics of the oscillating beam in the cavity are controlled, so that the oscillation of the fiber laser cutting machine established in the cavity is limited to a few intrinsic modes determined by the cavity, so as to improve the number of photons in a single mode, and obtain strong coherent light with good monochromity and good direction.

Laser is a kind of electromagnetic wave, the optical resonator of the laser will constrain the electromagnetic wave in a limited range of space, according to Maxwell electromagnetic field theory, in a certain range of space can only exist a series of split electrical advance wave eigenstates, these eigenstates are the mode of optical resonator, laser mode is the optical cavity can be distinguished electrical burst eigenstates, by the structure of the cavity.