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Abstract
BENJAMIN VACA. Anti-Reflective Structured Surfaces on Optical Windows Through Tunable Metallic Etch Masking (Under the direction of DR. ISHWAR AGGARWAL and DR. THOMAS HUTCHENS)The increasing output power of modern high-energy laser (HEL) systems necessitate robust optical components, particularly in military applications such as directed energy weapons (DEWs), medical procedures, and microfabrication. Traditional anti-reflective (AR) coatings can fail under high-energy conditions due to laser damage and delamination. An alternative solution, anti-reflective structured surfaces (ARSS), utilizes subwavelength features to create a gradient refractive index transition, effectively minimizing Fresnel reflection. Notably, random ARSS (rARSS) fabricated using sputtered discontinuous masking and plasma etching can achieve high laser-induced damage thresholds (LIDT), ten times higher than thin-film AR coatings. Moreover, rARSS is more practical for larger optics and the tunability of the peak spectral performance has been demonstrated by varying parameters in the fabrication process. This work explores the optimization of metal masking and reactive ion etching (RIE) parameters to enhance ARSS performance, capabilities, and scalability, by correlating fabrication parameters with ARSS feature characteristics and optical transmission. Finally, a "proof-of-concept" demonstration of successful random ARSS on a large diameter and thick optical window was performed and characterized. Overall, this work lays a foundation for further exploration and development of tunable ARSS, emphasizing scalability for larger optics and diverse substrate materials.