Description: Spectrum Scientific proposes that the next state-of-the-art technique for blazing diffraction gratings onto freeform surfaces is reactive ion beam etching. Compared to traditional blazing techniques such as ruling and holography, reactive ion beam etching enables the fabrication of high efficiency and low stray light gratings with a wider range of blaze wavelengths from the extreme ultraviolet to the infrared. Performing the reactive ion beam etching process on a freeform surface can reduce the number of optical components required through the combination of multiple surface functionalities, and in turn, reduce mission costs with the weight of the payload directly relating to the cost of launch. The application of aberration-corrected RIBE gratings to freeform surfaces has paradigm-shifting potential for both the functionality and feasibility of spaceborne instruments including CubeSat and SmallSat. The reactive ion beam etching technique used in this research will be based on the established process used in the semiconductor industry. Spectrum Scientific will apply the reactive ion beam etching process to a holographic diffraction grating and identify the parameters required to deterministically etch a specific blaze angle into the substrate. The methodology can then be translated to surfaces with higher complexities, including aspheric and freeform surfaces. The findings of this research will be targeted at low-cost and lightweight aerospace instrumentation, but they apply to all diffractive element users including the life science, photonics, and telecommunication industries.

Benefits: NASA systems require wide fields of view in small, lightweight packages. To enable this, complex surface functionalities, including diffractive optics and freeform mirrors must be employed. The development of reactive ion beam etched diffraction gratings on freeform surfaces could increase the efficiency and image quality of the NASA instruments. Traditionally, additional corrective optics are required to gain these improvements, but with the combination of the RIBE technique and the freeform surface, the number of components, and consequently the mass of the system are decreased. The low weight of the system will have the greatest advantages for low-cost missions including SmallSat and CubeSat where the cost of the launch directly relates to the mass of the payload. Another advantage of the reactive ion beam etched process is the freedom to blaze at any angle and for any wavelength with low scatter. This enables the development of extreme ultraviolet instruments that were previously limited by the groove profiles of ruled and holographic gratings.The market for optical gratings is well established and Spectrum Scientific currently ships over 30,000 diffraction gratings annually to a variety of customers in the life science, telecommunication, photonics, aerospace, and defense markets. Within these markets, higher performance and smaller form factors are market drivers and Spectrum Scientific is constantly looking at ways to meet these demands through innovative designs including freeform surfaces and novel fabrication techniques. The demand for freeform gratings with blaze wavelengths in the extreme ultraviolet to infrared range has been validated through an internal review of the markets, discussions with customers who have expressed an interest in this type of product or require the performance that a reactive ion beam etched freeform grating can deliver. There are only a small number of manufacturers of blazed holographic gratings globally, and Spectrum Scientific is the only company in the world that produces optically blazed gratings, using a proprietary blazing technique, which offers significant performance advantages compared to other manufacturers' gratings including higher ultraviolet efficiency and orders of magnitude lower stray light making us unique in our capabilities. Extending Spectrum Scientific's capabilities to produce highly efficient diffraction gratings for wavelengths in the extreme ultraviolet to infrared range through a reactive ion beam etching process would enable technological advancements for a wide array of instrumentation.