The word "laser" is a free translation of "Laser". Laser English original meaning Light Amplification by Stimulated Emission of Radiation, in China has been translated as "laser", "light laser device", "light stimulated radiation amplifier" and so on. In 1964, Academician Qian Xuesen's suggestion was adopted and the Chinese name "laser" was adopted, which not only reflected the scientific connotation of "stimulated radiation", but also indicated that it was a very strong new light source. Since then, the word "laser" has been recognized and is still used today.

Fiber lasers refer to lasers that use rare earth-doped glass fibers as gain media. Fiber lasers can be developed on the basis of fiber amplifiers. Under the action of the pump light, it is easy to form an increase in the power density in the fiber, causing the laser energy level of the laser working material to "reverse the number of particles". When properly added to the positive feedback loop (to form a resonant cavity), the laser oscillation output can be formed.

Fiber laser structure

The generation of laser signals requires three basic conditions: particle population inversion, optical feedback, and reaching the laser threshold. Therefore, the laser is composed of three parts: the working substance, the pump source, and the resonant cavity. The basic structure of a fiber laser is as follows. The gain fiber is the gain medium that generates photons; the pumping light is used as external energy to make the gain medium achieve population inversion, that is, the pump source; the optical resonator is composed of two mirrors. The function is to make the photon get feedback and be amplified in the working medium. The pumping light enters the gain fiber and is absorbed, which inverts the number of energy level particles in the gain medium. When the gain in the resonator is higher than the loss, laser oscillation will be formed between the two mirrors to generate a laser signal output. .

Features of fiber cutting

1. Good beam quality

The waveguide structure of the fiber determines that the fiber laser is easy to obtain a single transverse mode output, and is less affected by external factors, and can achieve high-brightness laser output.

2. High efficiency

Fiber lasers can achieve high light conversion efficiency by selecting semiconductor lasers that match the emission wavelength and the absorption characteristics of doped rare earth elements as the pump source. For high-power fiber lasers doped with ytterbium, 915nm or 975nm semiconductor lasers are generally selected, which have a longer fluorescence lifetime and can effectively store energy to achieve high-power operation. The overall electro-optic efficiency of commercial fiber lasers is as high as 30%-50%, which is conducive to reducing costs, energy saving and environmental protection.

3. Good heat dissipation

Fiber laser uses long and thin fiber doped with rare earth elements as the laser gain medium, and its surface area to volume ratio is very large. It is about 1000 times that of a solid block laser, and has a natural advantage in heat dissipation. In the case of medium and low power, no special cooling of the optical fiber is required. In the case of high power, water cooling is used to dissipate heat, which can also effectively avoid the degradation of beam quality and efficiency caused by thermal effects in solid-state lasers.

4. Compact structure and high reliability

Since the fiber laser uses a small and soft fiber as the laser gain medium, it is beneficial to compress the volume and save the cost. The pump source is also a semiconductor laser that is small in size and easy to be modularized. Commercial products can generally be output with pigtails. Combined with fiber-optic devices such as fiber Bragg gratings, all-fiber can be realized as long as these devices are fused with each other, which is environmentally friendly. High disturbance immunity and high stability save maintenance time and costs.

Fiber Laser Advantages

As a representative of the third-generation laser technology, fiber laser has the following advantages:

1. The advantages of miniaturization and intensification brought about by the low manufacturing cost of glass optical fiber, mature technology and the windability of optical fiber.

2. The glass material has an extremely low volume-to-area ratio, fast heat dissipation and low loss, so the conversion efficiency is high and the laser threshold is low.

3. The output laser has many wavelengths: this is because the energy levels of rare earth ions are very rich and there are many types of rare earth ions.

4. Tunability: Due to the wide energy level of rare earth ions and the wide fluorescence spectrum of glass optical fiber.

5. Since there is no optical lens in the resonant cavity of the fiber laser, it has the advantages of no adjustment, no maintenance, and high stability, which is unmatched by traditional lasers.

6. The optical fiber is exported, so that the laser can easily be used for various multi-dimensional arbitrary space processing applications, making the design of the mechanical system very simple.