Uncoated copper mirrors
We had a good opportunity to compare the performance of our gold-coated copper mirrors with uncoated copper ones recently. A customer sent us dozens of large water-cooled mirrors from his 6KW CO2 laser to re-manufacture. The effect of the workplace environment had dulled and corroded the bare copper mirror surfaces; simply handling them had caused stains on the mirror face. In comparison a gold-coated mirror, from exactly the same laser, had barely changed its appearance or performance.
We've also recently gained customers in tropical climates who had problems with any exposed copper on mirrors corroding, even in storage. Moisture reacts with exposed copper to cause pitting and staining, even through pinholes in dielectric coating like this example. Several OEMs are now specifying copper mirrors should be electroless nickel plated so no part of the mirror is exposed copper. This is already the case with all our gold-coated copper mirrors.
Some of our competitors are now warning that copper mirrors should be kept absolutely dry, which is simply impossible if they are to be used. Especially as some of them are water cooled!
Sub contract lapping
We have added a Mitutoyo Surftest to our metrology equipment and straight away used it to qualify the results on several jobs. A customer in the Middle East was struggling to find someone to lap a large profiled aluminium plate to 1um flatness and a high quality surface finish. We used our large diamond lapping machine and after measuring with the new instrument we had achieved Ra = 0.020um, Rq 0.029, and Rz 0.281um. A customer in the nuclear industry needed some tungsten carbide parts lapped and polished to a mirror grade finish. We processed some samples and the customer measured Ra 1 nanometre surface roughness after polishing.
Demand for diagonal mirrors in various forms seems to have surged recently. We have made traditional diagonal mirrors such as these gold-coated copper ones, although the diagonal angle here is 60 degrees. We’ve also made stainless steel versions with through holes for Laser Induced Breakdown Spectroscopy, and some small gold coated copper for Er:YAG surgical laser handpieces. Talking of surgical lasers, it seems being left handed can cause great difficulty for surgeons both in using surgical equipment designed for right handed surgeons and in being trained by right handed instructors. With lasers at least it’s possible to use a mirror to flip the beam paths and allow right handed and left-handed use.