This article introduces the working principle, application and advantages and disadvantages of YAG Laser and Fiber Laser.

Optical fibers are usually glass solid fibers drawn from SiO2 as the matrix material, and are mainly widely used in optical fiber communications. The principle of light guiding is the mechanism of total internal reflection of light. Ordinary bare fiber is generally composed of a central high-refractive-index glass core (the core diameter is generally 9-62.5um), the middle is a low-refractive-index silica glass cladding (the core diameter is generally 125um) and the outermost reinforced resin coating (see Fig. 1).

Optical fibers can be divided into single-mode fibers and multi-mode fibers. Single-mode fiber: The central glass core is relatively thin (9um+0.5um in diameter), only one mode of light can be transmitted, and its inter-mode dispersion is very small, and it has the functions of self-selecting and mode-limiting. Multimode fiber: The central glass core is thicker (50um+1um), which can transmit light in multiple modes, but its intermodal dispersion is large, and the transmitted light is not pure.

Fiber lasers have the characteristics of small size, low energy consumption, long life, high stability, maintenance-free, multi-band, green environmental protection, etc. It has won many laser Industry insiders affirmed. Fiber lasers have set new standards for the laser processing industry with their ultra-high reliability, excellent beam quality, and low operating costs.

It has long gain medium, high coupling efficiency, good heat dissipation, simple and compact structure, flexible and convenient use, good output laser beam quality and wide output wavelength range (400-3400nm)

High-power fiber lasers are all double-clad fibers. The pump light hits the outer cladding, and the energy is absorbed and partially converted into laser light. Therefore, the material and structure of the cladding have a great influence on fiber lasers. Optical fibers of various shapes, such as round, D-shaped, rectangular, unstable cavity, plum blossom, square, plane thread, etc.

This high-power wide-face multi-mode diode can work at very high temperature, only needs simple air cooling, and the cost is low.

The active cladding fiber in the high power fiber laser is doped with erbium/ytterbium rare earth elements, and has a wide and flat light absorption region (930-970nm), therefore, the pump diode does not require any kind of wavelength stabilization device

The pump light traverses the single-mode fiber core multiple times, so its utilization is high.

• The branched fiber is directly spliced and coupled for side pumping. First, no optical components are required. Second, it can avoid damage to the end face of the fiber. Third, it is easy to improve the injection of the pump source.
• Novel centipede-type side pumping method: many branches on both sides of the fiber are directly spliced with the LD pigtail, and single pumping from different points can avoid nonlinear effects and mode deterioration caused by a single point of strong laser light.
• Using multiple high-power LD single tubes instead of LD integrated arrays as the pump source, one can improve the mode of the light source, second, it is easy to dissipate the heat of the pump source and improve the lifespan, and third, it is conducive to maintenance and replacement.
• The use of LD (100-250us) with a wide luminous surface as the pump source can greatly reduce the optical power density of the LD light-emitting point and increase its life, generally up to 100,000 hours.

Fiber lasers consume only 1% of the power required by lamp-pumped lasers, while their efficiency is more than twice that of semiconductor-pumped solid-state lasers (Nd laser systems). The combination of higher efficiency, longer lifetime, and less maintenance makes the cost attractive to fiber laser owners. Fiber lasers are useful in laser applications that require high beam quality in the near-infrared. They will be particularly interested in small focused spots, high power density, such as tabletop production. A beam of 100W laser output spot can be focused as small as 5um, which is equivalent to a brightness of 109W/cm2. The current application positioning of fiber lasers includes: selective welding, marking, various artistic imaging, annealing, bending of micromechanical devices, cutting of 1~2mm stainless steel parts and other applications (related to power).

Fiber lasers have a wide range of applications, including laser fiber optic communication, laser space telecommunication, industrial shipbuilding, automobile manufacturing, laser engraving, laser marking, laser cutting, printing rolls, metal and non-metal drilling, cutting, welding, and fiber lasers can be used as Military laser beacon light source; in naval equipment, fiber lasers can be used for submarine communication, torpedo detection, sea depth measurement, underwater sensing and sea-based light-controlled weapons. Military national defense security, medical equipment and equipment, large-scale infrastructure construction, etc.

The price is relatively high, usually limited to the field of metal processing, and is unlikely to make a difference in non-metal processing. Materials such as plastic, paper or cloth. These industries will continue to be dominated by CO2 lasers

Advantages of fiber cutting compared to traditional laser cutting machines

It can be used for both plane cutting and bevel cutting, and the edges are neat and smooth. It is suitable for high-precision cutting of metal plates and glass. Compared with ordinary carbon dioxide laser cutting machines, it saves space and gas consumption, and has high photoelectric conversion rate. It is a new energy-saving and environmentally friendly product and one of the world’s leading technology products.

Fiber laser cutting machine has extremely high electro-optical conversion efficiency, its electro-optical conversion efficiency is 25%, which is several times higher than that of traditional laser cutting machine, and the comprehensive operating cost is only 15% of traditional laser cutting machine. At the same time, the fiber laser cutting machine is small in size, its laser generator covers an area of less than 1 square meter, and the overall area is about 50 square meters, which is two-thirds of the traditional laser cutting machine.

YAG laser is a solid-state laser based on yttrium aluminum garnet crystal. The chemical formula of yttrium aluminum garnet is Y3Al5O15, abbreviated as YAG.

Like other solid-state lasers, the basic components of YAG lasers are laser working material, pump source and resonator. However, due to the different types of activated ions doped in the crystal, different pump sources and pump methods, different structures of the resonators used, and different other functional structural devices used, YAG lasers can be divided into many types. For example, according to the output waveform, it can be divided into continuous wave YAG laser, repeated frequency YAG laser and pulse laser; YAG lasers (such as color center lasers), etc.; can be divided into Nd:YAG lasers, YAG lasers doped with Ho, Tm, Er, etc. according to different doping; Different output power (energy) can be divided into high power and medium and small power YAG lasers.

The solid-state laser cutting machine expands, reflects and focuses the pulsed laser beam with a wavelength of 1064 nm, and then radiates and heats the surface of the material. The surface heat diffuses to the interior through thermal conduction, and the width, energy, peak power and repetition frequency of the laser pulse are digitally controlled precisely. and other parameters, the material is melted, vaporized and evaporated in an instant, so as to realize the cutting, welding and punching of the predetermined trajectory through the numerical control system.

The machine has good beam quality, high efficiency, low cost, stability, safety, more precision, and high reliability.

• Fast processing speed, high efficiency and good economic benefits
• Small kerf on straight edge, smooth cutting surface, can obtain large aspect ratio and aspect ratio
• The thermal deformation is extremely small, and it can be processed on various materials such as hard, brittle, and soft
• There is no problem of tool wear and replacement, no mechanical change
• Easy to realize automation, can realize processing under special conditions

The pumping efficiency is high, up to about 20% (the lamp pumping efficiency is only a few percent). With the improvement of the efficiency, the thermal load of the laser medium decreases, so the beam quality is greatly improved and the lifespan is long (the lifespan of the LD reaches tens of thousands of hours, Pulse up to 1011 times), high reliability, small size, light weight, suitable for miniaturization applications.

Suitable for laser cutting, welding and drilling of metal materials: such as carbon steel, stainless steel, alloy steel, aluminum and alloys, copper and alloys, titanium and alloys, nickel-molybdenum alloys and other materials. Widely used in aviation, aerospace, weapons, ships, petrochemical, medical, instrumentation, microelectronics, automobiles and other industries. It not only improves the processing quality, but also improves the work efficiency; in addition, the YAG laser can also provide a precise and fast research method for scientific research.

• The YAG laser can work in two modes: pulsed and continuous. Its pulse output can obtain short pulses and ultra-short pulses through Q-switching and mode-locking technology, so that its processing range is larger than that of CO2 lasers;
• Its output wavelength is 1.06um, which is just an order of magnitude smaller than the CO2 laser wavelength of 10.06um, so it has high coupling efficiency with metal and good processing performance (the effective power of an 800WYAG laser is equivalent to 3KWCO2 laser power);
• The YAG laser has compact structure, light weight, easy and reliable use, and low maintenance requirements.
• The YAG laser can be coupled with the optical fiber. With the help of time division and power division multiplexing system, a beam of laser can be easily transmitted to multiple stations or remote stations, which is convenient for laser processing to achieve flexibility.

Therefore, in the selection of lasers, various parameters and their own actual needs should be considered. Only in this way can the laser exert its maximum efficiency.