We’ve recently published an article in our newsletter about an increase in demand for our mirror reworking service. This isn’t just idle boasting, it is a result of OEMs dramatically cutting support for installed CO2 lasers, including a big reduction in stocks of spare parts.
This is probably because the bulk of current OEM production is now focused on fiber lasers, therefore support for existing CO2 laser users has been cut. So at LBP we’ve seen a corresponding increase in demand for laser mirror repairs, not just for truly obscure mirrors but for parts that were standard and widely available just 2 or 3 years ago.
We regularly repair, polish and coat a wide range of mirrors, including copper and molybdenum, to a ‘good as new’ condition, saving our customers time and money.
Sometimes a high power infra red laser needs to have its power attenuated, or have strongly diverging modes removed from the beam. At Laser Beam Products we manufacture mirrors with precision through holes or with sharp knife edges that are very cost effective, even when made to your design as a one-off prototype.
We usually advise customers that the length of the hole is no more than the hole diameter, to avoid having a “tunnel” with an aperture at either end. We can make tapered holes to avoid this problem. Because our Gold coating is applied electrochemically the internal bore of any hole is also Gold coated.If an acousto-optic modulator (AOM) is being used, a reflective aperture can be used to manipulate one of the beam orders to be reflected and the other to be transmitted. We can make through holes as small as 1 mm diameter very accurately.
Some of our aerospace and automotive customers insist we offer a RTV (Return To Vendor) repair programme to reduce the overall cost of ownership of laser equipment. It saves time, money and valuable materials, and is well worth doing. The reworked mirrors are as good as new so there is no loss of quality or productivity. It can also contribute to ISO 14001 Environmental Management Here’s a great case study…
One of our customers, a European automotive manufacturer, sent us a collection of used mirrors from their production line that had accumulated minor burns and scratches, and had been swapped out. They were large, complex water cooled beam delivery mirrors which we repolished and recoated to a condition that was as good as new. The mirrors were repaired and returned in under 3 weeks.
The customer was delighted and told us the mirrors were working perfectly, and had saved them $15,000 on the cost of new mirrors!. They have since had them reworked three more times.
Here’s an example of another customer’s mirrors that we reworked to a ‘good as new’ condition. These were from a gas sensing cell made by a company who stopped supporting their equipment. You can find out more on our website.
It’s not widely appreciated how easy it is to distort a laser mirror with mechanical forces that can be generated from inadvertently over-tightening mounts, or water fittings. Although our experience is mostly with metal mirrors such as copper or aluminium, we know glass mirrors are just as sensitive to distortion. Sometimes the distortion is elastic, so the surface figure is restored when the mechanical force is removed. Often though the distortion can be permanent. We recently repaired a water cooled mirror for a customer that was very thick ( 33mm ) and looked to be in good condition.
By reflecting a high mode quality visible laser beam from the mirror at 45 degrees incidence we could see the distortion the mirror introduced into the reflected beam profile. Using our phase shifting interferometer we could resolve a 2-3mm diameter convex ‘pip’, perhaps just a micron or so high, in the centre of the mirror. This is where the surface had been ‘punched through’ by the mounting screw in the rear of the mirror.
There was 16 mm thickness of solid copper between the bottom of the screw hole and the mirror face. Despite this though, it was still possible for the mechanical force from tightening of the mounting screw to permanently distort the mirror face.
The hot spot created in the reflected beam by the mirror distortion when used with a CO2 laser would have likely caused damage to other optics, such as the focus lens.
We have recently developed the gold coating of carefully roughened metal substrates to be used as diffuse reflectors. This particular example, based on Aluminium, has a consistent surface roughness of Ra=6um and would be useful in the near infra red.
The surface roughness needs to be random enough to allow the surface to function as an isotropic diffuse reflector for infra red wavelengths. Additionally the magnitude of the surface roughness needs to be high enough so the reflectance will be perfectly diffuse and have no enhanced reflectance in the specular direction. We are happy to coat customer supplied material and we can provide measurements of the surface texture.