Fiber laser refers to a laser that uses rare earth-doped glass fiber as a gain medium. Fiber laser can be developed on the basis of fiber amplifier: under the action of pump light, it is easy to form high power density in the fiber, causing laser The laser energy level of the working material is "number inversion", and when a positive feedback loop (constituting a resonator) is properly added, the laser oscillation output can be formed.
(1) The beam quality is good.
fiber-optic laser
The waveguide structure of the fiber determines that the fiber laser is easy to obtain 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-to-light conversion efficiency by selecting semiconductor lasers with matching emission wavelengths and absorption characteristics of doped rare-earth elements as pump sources. For ytterbium-doped high-power fiber lasers, 915 nm or 975 nm semiconductor lasers are generally selected, which have a longer fluorescence lifetime and can effectively store energy to achieve high-power operation. The overall electro-optical efficiency of commercial fiber lasers is as high as 25%, which is conducive to reducing costs, saving energy and protecting the environment.
(3) Good heat dissipation characteristics.
Fiber lasers use slender rare-earth element fibers as laser gain media, which have a very large surface area to volume ratio. It is about 1000 times that of solid-state bulk lasers, 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 effectively avoid the reduction of beam quality and efficiency caused by thermal effects commonly seen in solid-state lasers.
(4) Compact structure and high reliability.
Since the fiber laser uses a small and flexible 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 Bragg gratings and other fiber-optic devices, as long as these devices are welded to each other, all-fiber lasers can be realized. High disturbance immunity and high stability save maintenance time and expense.
As a representative of the third-generation laser technology, fiber lasers have the following advantages:
(1) The advantages of miniaturization and intensification brought about by the low manufacturing cost of glass optical fibers, mature technology and the windability of optical fibers;
(2) The glass fiber does not require strict phase matching like crystal for the incident pump light, which is due to the wide absorption band caused by the non-uniform broadening caused by the Stark splitting of the glass matrix;
(3) The glass material has a very low volume-to-area ratio, fast heat dissipation and low loss, so the conversion efficiency is high and the laser threshold is low;
(4) There are many output laser wavelengths: this is because the energy levels of rare earth ions are very rich and there are many types of rare earth ions;
(5) Tunability: due to the wide energy level of rare earth ions and the wide fluorescence spectrum of glass fibers.
(6) Since there is no optical lens in the resonant cavity of the fiber laser, it has the advantages of adjustment-free, maintenance-free and high stability, which is unmatched by traditional lasers.
(7) The fiber export makes the laser easily competent for various multi-dimensional arbitrary space processing applications, which makes the design of the mechanical system very simple.
(8) Competent in harsh working environment, with high tolerance to dust, shock, shock, humidity and temperature.
(9) No need for thermoelectric cooling and water cooling, just simple air cooling.
(10) High electro-optical efficiency: The comprehensive electro-optical efficiency is as high as 20% or more, which greatly saves power consumption during work and saves operating costs.
(11) High power, commercial fiber lasers are six kilowatts.
1. Marking application
Pulsed fiber lasers are the easiest and most flexible way to use without water cooling due to their excellent beam quality, reliability, longest maintenance-free time, highest overall electro-optical conversion efficiency, pulse repetition frequency, smallest volume, and lowest operation The cost makes it the only option for high-speed, high-precision laser marking.
A fiber laser marking system can consist of one or two fiber lasers with a power of 25W, one or two scanning heads for guiding light to the workpiece, and an industrial computer that controls the scanning heads. This design is more than 4 times more efficient than splitting the beam from one 50W laser to two scan heads. The maximum marking range of the system is 175mm*295mm, the spot size is 35um, and the absolute positioning accuracy within the full marking range is +/-100um. The focus spot at 100um working distance can be as small as 15um.
2. Application of material handling
The material treatment of fiber lasers is based on a heat treatment process in which the parts of the material that absorb the laser energy are heated. Laser light energy with a wavelength of about 1um is easily absorbed by metals, plastics and ceramic materials.
3. Application of material bending
Fiber laser forming or bending is a technique used to alter the curvature of metal sheets or hard ceramics. Concentrated heating and rapid self-cooling lead to plastic deformation in the laser-heated area, permanently changing the curvature of the target workpiece. The study found that microbending with laser processing has far higher precision than other methods, and it is an ideal method in microelectronics manufacturing.
4. Application of laser cutting
As the power of fiber lasers continues to rise, fiber lasers can be applied on a large scale in industrial cutting. For example: micro-cutting stainless steel arterial tubes with a fast chopping continuous fiber laser. Due to its high beam quality, fiber lasers can achieve very small focusing diameters and the resulting small kerf widths are setting new standards in the medical device industry.
