Polishing Iridium Coatings for Zero-Net-Stress

Research on the topic of coating silicon mirrors with iridium has shown that the task of reducing coating stress to minimize mirror distortion remains a subject of continuous study and an area of ongoing improvement. Many efforts have been pursued on the deposition of iridium in a manner that aims to reduce and/or balances coating stress, including bi-layer deposition with chromium and iridium, front and back coating, heat treating, annealing, ion beam figure correcting and atomic layer deposition. It has been determined through our investigation of this topic that one of the simplest and most effective ways to coat these optics in a distortion-free manner is by using the atomic layer deposition ALD coating method. ALD offers 3 main advantages including lower operating temperatures, simultaneous front and back coating and accurate thickness. These advantages allow the iridium coating to be deposited without distorting the mirrors, but the trade off is an increase in surface roughness that can be twice as high as the desired 0.4-0.5 nm RMS specification required for X-Ray mirrors. OptiPro is proposing that their Elastic Emission Machining (EEM) process be used as a solution for smoothing these ALD iridium coated thin mirrors and consequently solving the issue of thin mirror distortion. EEM is capable of atomic-level machining that does not inject heat into the surface, nor does it damage the atomic lattice structure, which as a result leaves a very smooth surface and prevents sub-surface damage. These attributes of EEM also include a precision polishing tool that greatly reduces the risk of inducing mid-spatial frequencies onto the surface, making it an ideal method for accurately smoothing the rougher iridium surface that results from ALD coating.

The main objective for this proposal is to help address challenges associated with the lens distortion that occurs on iridium coated X-ray thin mirrors. It has been found through our research that the only way to create iridium coated X-ray thin mirrors without distortion is to utilize atomic layer deposition (ALD). The issue found with ALD is that the resulting surfaces of these coated mirrors is above the desired 0.4-0.5 nm RMS roughness spec for X-ray optics. OptiPro is proposing that our Elastic Emission Machine be employed as tool for smoothing out the iridium coated mirrors and as a result, become part of the solution for mitigating the lens distortion that can occur when iridium is coated on thin silicon mirrors. It is documented that these thin mirror optics will be directly involved in the future proposed X-ray telescopes and the quantities of these lens could be in the tens of thousands. OptiPro is interested in selling Elastic Emission Machining as a service to companies that may have difficult surfaces, tight tolerances or rare materials. The work done from the proposed SBIR will further our understanding of how to handle these unique processes/materials and will translate over to the precision required for fabricating next generation precision optics. The iridium coating in this proposal is particularly challenging due to its unique properties and the accuracy required for removing a partial layer of nm thick coating will require the optimum level of precision. As part of the growth of OptiPro, Elastic Emission Machining is under development as a sub-business within the OptiPro company. Note this business is not a distinct entity, but just an organization with its own accounting and managerial system within OptiPro. This business is currently called “400”, as it is the wavelength of light in nanometers – and shorter – that will drive the development of the next generation of optical fabrication and metrology equipment. We feel that it is important to emphasize that OptiPro is heavily involved with developing both fabrication and complimentary metrology systems operative at the nanometer level.

This is a mature technology (TRL 7+) — the realistic path in is usually NASA's Technology Transfer Program: licensing an existing NASA patent, or a Space Act Agreement to use NASA facilities/expertise directly. NASA also runs a startup licensing program with no upfront fee for companies formed to commercialize a specific NASA technology.

None of these are guaranteed paths for this specific project — TechPort itself doesn't have an "apply" button. Reaching out to the contact(s) above with a specific question is usually the fastest way to find out what's actually open.