Principle of fiber laser
Fiber optic is SiO2 as the matrix material pulled into a glass solid fiber, its light-guiding principle is the use of the principle of total reflection of light, that is, when the light is greater than the critical angle of angle from the refractive index of light dense medium to the refractive index of light sparse medium, will occur in total reflection, all the incident light is reflected back to the refractive index of the light dense medium, refractive index of the light sparse medium will have no light through the refractive index of light sparse. The light sparse medium with small refractive index will have no light transmission. Ordinary bare optical fiber is generally composed of a high refractive index glass core in the center, a low refractive index silica glass cladding in the middle, and a reinforced resin coating on the outside. Optical fibers can be divided into single-mode fibers and multi-mode fibers according to the mode of propagation of light waves. Single-mode fiber core diameter is small, can only propagate a mode of light, its intermode dispersion is small. Multimode fiber core diameter is thicker, can propagate a variety of modes of light, but its intermodal dispersion is larger. According to the refractive index distribution of the case of points, can be divided into step refractive index (SI) fiber and gradient refractive index (GI) fiber.
The rare earth doped fiber laser, for example, doped with rare earth ions in the fiber core as a gain medium, doped fiber is fixed between the two mirrors to form a resonant cavity, the pump light from the M1 is incident into the fiber, from the M2 output laser. When the pump light passes through the fiber, the rare-earth ions in the fiber absorb the pump light, and their electrons are excited to a higher excitation energy level, realizing the ion number inversion. The inverted particles are transferred from the higher energy level to the ground state by radiation formation, outputting laser light.
Fiber laser, as a representative of the third generation of laser technology, has the following advantages
(1) the advantages of miniaturization and intensification brought about by the low cost of glass fiber manufacturing, the maturity of the technology and its fiber sparing;
(2) the glass optical fiber does not require a strict phase matching for the incident pumping light as in the case of crystals,
(3) the glass material has an extremely low volume-to-area ratio, fast heat dissipation, low loss, so the conversion efficiency is higher,
(4) output laser wavelengths: this is because of the rare earth ion energy levels are very rich and its rare earth ion species;
(5) tunability: due to the wide energy levels of the rare earth ions and the wider fluorescence spectrum of the glass fiber
(6) due to the resonance cavity of the fiber laser no Optical lenses, has the advantages of adjustment-free, maintenance-free, high stability, which is unmatched by traditional lasers.
(7) Fiber export makes the laser easily capable of various multi-dimensional arbitrary spatial processing applications, making the design of the mechanical system very simple.
(8) Competent in harsh operating environments, with high tolerance for dust, vibration, shock, humidity and temperature.
(9) No need for thermoelectric cooling and water cooling, just simple air cooling
(10) High electro-optical efficiency: the integrated electro-optical efficiency is up to 20% or more, which substantially saves power consumption at work and saves operating costs.
(11) high power, commercial fiber laser is six kilowatts.