Creating Blazed Gratings for Freeform Mirror Surfaces

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.