Fabrication of next-generation reflection gratings for use in ultraviolet astronomy

Observations of ultraviolet (UV, 900 – 2000 Å) spectra are imperative to the continued pursuit of a complete, multi-wavelength understanding of the Universe. To enable better measurements for future science goals, technology developments in all components of UV space missions are required. This thesis is motivated, in particular, by the requirements defined for future UV diffraction gratings. Gratings are a critical spectrometer component and are a limiting factor on the maximum possible resolution and efficiency of an instrument. Improvements to UV diffraction gratings can enable observation of important molecular and atomic absorption lines which are historically challenging to observe due to the density of their spacing and the reduction of signal via attenuation through space. Thus, the primary objective of this dissertation is to determine the most appropriate method for fabricating large-area, high-resolution, and highly efficient blazed gratings for use in UV astronomy. To accomplish this goal, fabrication techniques borrowed from the semiconductor industry including electron beam lithography (EBL), nanoimprint lithography (NIL), and potassium hydroxide (KOH) wet-etching were employed. Metrology, both conventional in the field of fabrication (SEM, AFM, and optical microscopy) and unconventional (interferometry) were used. Through an iterative fabrication and metrology process, a wide parameter space of techniques was explored and the most effective methods for data preparation, patterning, and etching were determined. The primary deliverable of this thesis is a cm $\times$ cm grating which is patterned via EBL, transferred, and blazed into silicon to a UV relevant angle via KOH etching. The grating will be characterized via interferometric metrology to determine its limiting resolution and delivered to collaborators for at-wavelength UV efficiency measurements. Results on replication of gratings for large missions via NIL are also detailed. Finally, efforts to model imperfectly fabricated gratings via Fourier optics are reported.