Super Hard Coating Technology note

Why the SHC, Laser Point's Super Hard Coating, is the hardest available on the market

Damage Thresholds on Laser Absorbers

LaserPoint has always been well known for the robustness of its absorbers and the SHC coating is the last entry in the family of hard coatings for laser radiation. Performances of SHC are stunning and definitely place it to be the best laser coating available on the market, today. What defines the goodness of a laser coating is its behavior when it is subject to high powers or energy densities, thus to small, converging or focused beams or when it undergoes to pulsed lasers with narrow pulse durations. Because of its importance, the limit value of power or energy that an absorber can withstand before it gets damaged is always available on power/ energy sensors specifications in term of Max. Power/Energy density (respectively expressed in W/cm2 and J/ cm2). Which are the consequences of a situation where that limit value has been exceeded ? The first and immediate is that the coating is damaged (it can be at different degrees) and measurements are no longer reliable. A second consequence is that the sensor might be so much damaged to need replacement. A common habit in the market is to advertise always the highest power/energy densities in a way where the highest has to be identified as the best. But is this the correct approach to present data? It is not so, as it can be understood by the graph above. ( Competitor’s Data available on 2011 Catalogs). This shows, for various coating types of different Manufacturers, how power density varies with the change of laser power. In general and without entering in the complicate physics of materials and heat transfers, it emerges from the graph that materials used by various suppliers all behave in the same way, which says that the curves display a behavior common to all materials. It can also immediately be seen that the lower the laser power is, the highest the power density will be; in other terms, by providing information related to low laser powers some Suppliers can claim exceptional performances. Specifications readers are then sent to the footnotes of datasheets just to realize that measures have been taken at 7 or 10W, which obviously is a limited information if the sensor is, for example, for 200W . Those high values can then be a strong commercial point but do not necessarily correspond to the coating quality and to the real absorber performance. Mechanisms of heat transfer are complex and related to materials, sensors’ geometries and cooling efficiencies; they are so complex that the same coating behaves differently whether the sensor on which it is deposited is air cooled or water cooled. A correct information should thus present the maximum power or energy density at the maximum power or energy the sensor is specified for. In the example above, ratings should be supplied at 200 W. All these pictures then give the idea of why it is so important to provide customers with correct and comfortable specifications for laser absorbers, in particular on those regions where their use is at the limit for materials (e.g. high powers, small beams).

SHC’s test campaigns made with Customers

Laser Point’s specification curves for the SHC are based on test campaigns made with our Customers in disruptive conditions and show that the properties of SHC are steps ahead any other coating: it withstands more than 12KW/ cm2 with an applied power of 1KW of Yag laser in CW operation, or 40J/cm2 with peak powers of 3.2 KW @1 msec on laser diodes! The SHC has also a very high absorption ratio ( > 85%) over an extended working range ( 0,25μ to 25μ), making it suitable for safe applications in almost all laser domains.

To conclude: in your selections of laser detectors, always consider that absorbers are not a detail but one of the most important elements in a laser measuring device. They are the first element the beam meets and, if the beam is too small, or the mode is a sharp Gaussian ( as it is, for example, the case of slab lasers) or the beam includes dangerous hot spots, then the sensor might easily be damaged. At the end, not only the measurements will be invalided, but it’s also time and money that will go because a damaged head will need to be serviced or substituted. For these reasons, we are committed in providing clear , easy to understand specs and work to develop new technologies for more reliable products also for harsh environments.