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Fiber laser technology development trend in future
- Mar 23, 2016 -

Fiber laser technology development trend in future

Fiber laser has many benefits, such as long life, low complexity, reduce operating costs and low maintenance requirements. Today, in many of the fiber-based products, and the application needs to find the power level of the carbon dioxide laser used in the past matches the fiber laser.

Fiber lasers thanks to Elias Snitzer earliest in 1961, and in 1962 by the US General Electric Company (GE) and International Business Machines Corporation (IBM) of the two groups, the first demonstration of the coherent light emitted from a semiconductor diode (first station diode laser). Since then, the power level of fiber laser technology can be greatly improved, reaching maturity, "historic" level of carbon dioxide laser technology. It is in this 50 kilowatts average power magnitude difference technology leads to the sharpest focus: a carbon dioxide laser 50 kilowatts of small houses occupy a space, and a 50-kW fiber laser only with close to a large freezer space.

Other benefits of fiber lasers, for example, easy to use, simple structures, near-zero maintenance, high efficiency and low operating cost, has been widely accepted. Because some users will prefer the familiar products and technologies, as some users would rather have been using familiar products and technologies, as well as the relationship has been established between the holding and laser suppliers, CO2 technology currently used is always difficult to be replaced.

Fiber laser structure

Fiber laser comprises a series of optical fiber spliced together physical means, so that the laser beam does not leave the optical fiber cable element, until the laser beam emerging from the focus of the optical fibers to the workpiece. When this method works with the use of single emitter pump diode combination, the result is obtained the most powerful and longest laser tool. MTBF single emitter pump diode (MTBF) life of 300,000 hours. Although this is the basis of reliable statistics, but these values are too high, some incredible laser users. Perhaps, given the credibility of these typical life time value of a lack of telecommunications, at least in part because of the use of diode bars or diode stacks as to pump life time. Just before the advent of fiber lasers, diode bars to many, especially to make the diode pump solid state stack (DPSS) laser, which is rather poor reputation for reliability.

Fiber laser technology faces many challenges: the sensitivity to back reflection; over time, the mysterious effect of dark photons or fiber degradation; and, more recently cognitive, cutting thickness greater than 15 mm of materials, various infrared (IR ) difference in solid-state lasers (both fiber and plate), and between the carbon dioxide laser. While a complete explanation of solving these problems is beyond the scope of this article, but all of these problems have now been resolved.

Development of low-power fiber lasers

Due to the large volume sales in the lineage of the high and low ends of the power consumption has been achieved vertical integration of the economies of scale achieved. In the low power level, sales of low-power fiber lasers has led to flash pump laser marking machine sales eclipsed. Has sold tens of thousands of such low power devices, almost every manufacturer has a marking system based on fiber laser marking machine in its product lineup.

Fiber laser has been necessary in-depth understanding of the scientific basis, covering the entire range of laser power, strict control of each individual fiber laser system based on a fiber optic component specifications. This has led to a build can be mixed and matched to form a wide range of fiber laser components of the large "toolbox." Ultrashort pulse laser industry is briefly examine the production and use of fiber laser product family illustrates this point.

Low average power in the field, this scalable modular technology go from here? The answer, in many different directions. In the low-power end product category, we will introduce some, but not all directions.

Millisecond to nanosecond pulsed fiber laser

Until recently, the standard nanosecond laser marking module has been able to meet most general laser marking applications. The laser power on the order of 50 watts, with the same footprint, no brightness decay.

Require high average power and high brightness combinations, maintain the table shown high ablation efficiency. In fact, these same laser derivative products, can provide up to 500 watts of average power, pulse energy of 50 mJ. This laser is the most exciting new applications, including high-speed clearing a range of films and coatings. 20 watts of power on the order of variable pulse length of fiber master oscillator power amplifier (MOPA) system for many years, and its short pulse length to 4 nanoseconds. Until recently, because users become more familiar with advanced laser marking technology, this additional refinement to get appreciation. One example is the use of low-nanosecond laser, almost entirely in black marker polycarbonate sub-surface is formed, which meets the minimum requirements for the application of surface damage. This process Another interesting development is the use of polymers for subsequent welding process the same nanosecond infrared laser, use this tag as an absorber.
For another example of the metal it is called a "dark mark" technology. This is known as medical devices for industrial use on stainless steel parts with high contrast, hard to wipe corrosion mark you. This technique is commonly used in the technically correct term is not "annealing mark." In this case, a high repetition rate using a low-power laser technology to ensure a variety of stainless steel surface of the high points of overlap and uniform, localized heating, resulting in smooth, crack-free, but with high contrast corrosion resistant coating . Because there is no interruption surface, this particular marker is widely used for surgical instruments. While it was generally believed that in each case the preferred short pulse length or duration of the pulse, but the pulse length is only one of several important variables involved in this process to: also requires a certain magnitude and pulse energy flux or the peak power density, that is, the importance of the brightness. Already have this type of laser is the next generation of products, the M2 as low as 1.2 (Some would call it a single-mode), pulse length to 1 nanosecond peak power of 40 kilowatts. Shape picosecond will come out in early 2012.

Microsecond to millisecond high pulse energy fiber laser

Another recent development is called quasi-continuous-wave (QCW) fiber laser. This is the concept of fiber lasers into the fiber laser pump laser flash technology, one of the last bastions of another extension: high pulse energy, low duty cycle laser processing. In this case, vertical integration and cost-effective pump diode manufacturing, nonlinear thresholds understanding and careful design, has been able to create the maximum pulse energy of 60 joules can be flexibly adjusted series lasers. 150 watts minimum power level lasers, pump lasers with flash the same 10 ms pulse length, has the ability to 15 joules and 10 Hz.

In the single-mode fiber can really produce this 60 Joule pulse energy? Obviously, the problem now have a definite answer, but in the real world there are very few applications actually need such a pulse energy levels. Tests showed that the laser can generate not only the type of many low-power applications require large nuclear welding weld diameter, but also to cut a few millimeters thick, highly reflective material, such as aluminum and copper.

Millisecpmd pulse shaping in time quasi-continuous-wave lasers latest capacity increase, is called pulse signal generator (PSG) laser control package, allowing for the vast number of complex pulse time programming. Many years ago, the time had been widely used to control the pulse pump laser flash, and deemed essential for some spot welding applications. In order to prevent the laser spot-weld the ends overlap and appear related to the collapse of porous pseudo keyhole loose, requiring laser pulse at the end there is a slow ramp drops, rises this demand. In this case the advantages of fiber lasers is a diode pump having a pump laser flash than conventional flash used a shorter ON time. Therefore, it is possible to use a shorter pulse length of the incremental part, and the more complex waveforms.

For dissimilar metal welding and high reflectivity metal welding and other complex micro-welding (microwelding) technology, pulse shaping capability is very important (see Figure 4). Compare two temporal pulse shape effects, showing the advantages of standard waveforms located above Eglise (Eglise) waveform (see Figure 5). Temporal pulse shape and can each pulse, the welding applications for fine adjustments to improve the curing conditions. Future reports will further metallurgical analysis. Given the lack of condensation forming concentric ripples and spot welding in a single shot down the center of the line, it is recommended to adopt a stronger damping during the curing process.

Figure 4 pulse signal generator (PSG) generated Eglis pulse waveform

Figure 5 shows a) a standard 10 millisecond square wave pulse and b)

Trailing with 8 ms 10 ms Eglise (Eglise) pulse shape. Lack condensed concentric ripples and single-shot spot-reduced center line diagram (b) shown in the curing process is recommended to adopt a stronger damping

Longer wavelength fiber laser

Emission spectrum in the range of 1.5 to 2 microns erbium and thulium laser rod has existed for some time, but have not previously been used for material processing. Over the years, various modifications have been high brightness fiber lasers for a variety of medical and aerospace applications.

Many of these polymers with increasing wavelength in the absorption capacity; recently only been determined, the absorption of this magnitude suitable for welding transparent polymer, thereby eliminating the need for the specific infrared absorbing agent. When using high-brightness single-mode lasers, even collimated beam can generate sufficient power density to form a high-quality optical transparent connection in the form of overlapping and welding butt in. It shows the absorption of several types of polymers in the table.

These advances with impressive speed, fiber laser proved the concept inherent scalability. Fiber laser experts are fully aware of the non-linear threshold involved, it is possible to add more fiber and more pump diodes to achieve greater power expansion.