Low absorption, anti reflection coatings are critical to the performance, reliability and lifetime of optics used is high power fiber lasers. High-power kilowatt-level fiber lasers operating between 1.0 and 1.1 µm find frequent use in macro-materials processing applications, such as cutting and welding metal sheets. The nature of these applications requires laser optics to perform properly at correspondingly high laser powers and power density levels. Minimizing losses due to absorption is therefore of crucial importance to laser reliability and performance. Achieving this requires a clearer understanding of the materials, coating technologies, and measurement techniques used for the manufacturer of high-performance, low-absorption fiber laser optics.
Lens coatings are an essential part of high-power CO2 laser systems. Coatings must protect the lens and allow for the highest levels of optical performance, with low levels of absorption and a long life expectancy. Transparency is another coveted characteristic for use with visible HeNe red laser pointers. The cost/benefit ratio of a coating must also be considered, as well as the environmental impact of the substrates used. For optical manufacturers, the challenge is in developing a lens coating that excels in all of these areas.
Presenting the new technologies, optical elements and their functionalities to help you reach a more efficient cutting:
- Annular beam - improve cutting speed and cutting quality, particularly in thick materials
- Motorized continuous zoom lens - suitable for variable spot sizes, fits the full range of required sheet thicknesses, efficient cutting at each sheet thicknesses.
High power lasers are a growing industry with numerous applications. As 1 μm fiber laser technology advances and more demanding applications develop, the optics used in such systems must provide superior levels of performance.
During laser operation with several kilowatts, the focusing lens is heated because it absorbs a small portion of the laser power. The anti-reflection (AR) coating was developed for CO2 lenses many years ago when lasers were lower powered than they are now. They were the best coatings available for many years. Now, of course, the average laser machine is no longer 1K to 2.5K, but can be up to 5 or 6K or more. These equipment improvements required that new optical coatings be developed to handle the thermal demands of higher power.
There are a number of articles that you can find on the web that discuss the comparisons of the CO2 performance to the fiber laser. It has been covered by a number of well-respected industry magazines. There is no longer a discussion about if fiber will be able to compete with CO2. Some of the OEMs have already reached the tipping point and are selling more fiber lasers than CO2.
Focal length and mounting distance
In general, there are two types of focusing lenses: planoconvex lenses which have one convex surface (convex = dome-like curvature) and one flat surface, and meniscus lenses which have one convex surface and one concave surface (concave = hollow curvature). In most laser cutting machines, meniscus lenses are used because they produce a smaller focus diameter (see next section). In some machines, plano-convex lenses are used because their production costs are a little bit lower.
During laser operation with several kilowatts, the focusing lens is heated because it absorbs a small portion of the laser power. Absorption takes place mainly in the AR (Anti Reflection) coatings and at dirt on the lens.
At a new clean lens with standard AR coating, absorption is typically 0.2% of the incoming laser power. A lens with Ophir's Black MagicTM coating initial absorption is guaranteed to be less 0.15%.
In our newest type of lenses the Clear Magic, the Max absorption is lower than 0.13% and the typical absorption is 0.10% and lower