Browsing by Author "Carfagno, Henry"
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Item An image analysis method for quantifying precision and disorder in nanofabricated photonic structures(Nanotechnology, 2022-11-28) Carfagno, Henry; Garcia, Pedro David; Doty, Matthew F.Disorder is an essential parameter in photonic systems and devices, influencing phenomena such as the robustness of topological photonic states and the Anderson localization of modes in waveguides. We develop and demonstrate a method for both analyzing and visualizing positional, size, and shape disorder in periodic structures such as photonic crystals. This analysis method shows selectivity for disorder type and sensitivity to disorder down to less than 1%. We show that the method can be applied to more complex shapes such as those used in topological photonics. The method provides a powerful tool for process development and quality control, including analyzing the precision of E-beam lithography before patterns are transferred; quantifying the precision limits of lithography, deposition, or etch processes; and studying the intentional displacement of individual objects within otherwise periodic arrays.Item Inverse Designed Couplers for Use in Gallium Arsenide Photonics(ACS Photonics, 2023-05-17) Carfagno, Henry; Guidry, Melissa A.; Yang, Joshua; McCabe, Lauren; Zide, Joshua M. O.; Vučković, Jelena; Doty, Matthew F.Highly efficient photonic couplers are a necessary component of a scalable platform to couple quantum emitters into quantum fiber networks. We inverse-designed couplers for use in gallium arsenide membrane-based photonics that are compatible with indium arsenide quantum dots, one of the highest quality quantum light sources available. We fabricated and tested at least 4 instances of devices following 11 different designs. All inverse-designed structures outperformed the traditional grating outcoupler in a single-mode optical fiber optical setup. Using a novel sleeve and bulk fabrication method allowed for a smaller allowable minimum feature size constraint in the inverse design optimization protocol. Employing this new design constraint improved the average device transmission efficiency from 17.4% to 27.5%. The use of broadband optimization criteria did not result in statically significant improvement in actual bandwidth, but did decrease the variance in the measured bandwidth, suggesting a more robust design.Item A sleeve and bulk method for fabrication of photonic structures with features on multiple length scales(Nanotechnology, 2022-09-21) Carfagno, Henry; McCabe, Lauren; Zide, Joshua; Doty, Matthew F.Traditional photonic structures such as photonic crystals utilize a) large arrays of small features with the same size and pitch and b) a small number of larger features such as diffraction outcouplers. In conventional nanofabrication, separate lithography and etch steps are used for small and large features in order to employ process parameters that lead to optimal pattern transfer and side-wall profiles for each feature-size category, thereby overcoming challenges associated with RIE lag. This approach cannot be scaled to more complex photonic structures such as those emerging from inverse design protocols. Those structures include features with a large range of sizes such that no distinction between small and large can be made. We develop a sleeve and bulk etch protocol that can be employed to simultaneously pattern features over a wide range of sizes while preserving the desired pattern transfer fidelity and sidewall profiles. This approach reduces the time required to develop a robust process flow, simplifies the fabrication of devices with wider ranges of feature sizes, and enables the fabrication of devices with increasingly complex structure.