Working principle of fiber laser！

Working principle: Optical fiber is a solid glass fiber drawn with SiO2 as the matrix material. Its light guiding principle is to use the total reflection principle of light, that is, when light is incident from a light-dense medium with a large refractive index to a light-sparse medium with a small refractive index at an angle greater than the critical angle, total reflection will occur, and the incident light will be completely reflected to the light-dense medium with a large refractive index, and no light will pass through the light-sparse medium with a small refractive index.

Ordinary bare optical fiber is generally composed of a central high-refractive index glass core, a low-refractive index silicon glass cladding in the middle, and an outermost reinforced resin coating. Optical fibers can be divided into single-mode optical fibers and multi-mode optical fibers according to the propagation light wave mode.

Single-mode optical fibers have a smaller core diameter and can only propagate one mode of light, and their inter-modal dispersion is small. Multi-mode optical fibers have a thicker core diameter and can propagate multiple modes of light, but their inter-modal dispersion is larger. According to the distribution of refractive index, they can be divided into step-index (SI) optical fibers and graded-index (GI) optical fibers.

The pump light emitted by the pump source is coupled into the gain medium through a reflector. Since the gain medium is a rare earth-doped optical fiber, the pump light is absorbed, and the rare earth ions that absorb the photon energy undergo energy level transitions and achieve particle number inversion. The inverted particles pass through the resonant cavity and transition from the excited state back to the ground state, releasing energy and forming a stable laser output.

The working principle of the fiber laser is mainly based on the special structure of the fiber laser. The laser is composed of three parts: working material, pump source and resonant cavity. The specific functions are as follows:

1. The gain fiber is the gain medium that generates photons.

2. The role of the pump light is to act as external energy to make the gain medium achieve particle number inversion, that is, the pump source.

3. The optical resonant cavity is composed of two reflectors, which are used to make the photons get feedback and be amplified in the working medium.

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