Browsing by Author "Zide, Joshua M. O."
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Item Band Engineering of ErAs:InGaAlBiAs Nanocomposite Materials for Terahertz Photoconductive Switches Pumped at 1550 nm(Advanced Functional Materials, 2024-04-18) Acuna, Wilder; Wu, Weipeng; Bork, James; Doty, Mathew F.; Jungfleisch, M. Benjamin; Gundlach, Lars; Zide, Joshua M. O.Terahertz technology has the potential to have a large impact in myriad fields, such as biomedical science, spectroscopy, and communications. Making these applications practical requires efficient, reliable, and low-cost devices. Photoconductive switches (PCS), devices capable of emitting and detecting terahertz pulses, are a technology that needs more efficiency when working at telecom wavelength excitation (1550 nm) to exploit the advantages this wavelength offers. ErAs:InGaAs is a semiconductor nanocomposite working at this energy; however, high dark resistivity is challenging due to a high electron concentration as the Fermi level lies in the conduction band. To increase dark resistivity, ErAs:InGaAlBiAs material is used as the active material in a PCS detecting Terahertz pulses. ErAs nanoparticles reduce the carrier lifetime to subpicosecond values required for short temporal resolution, while ErAs pins the effective Fermi level in the host material bandgap. Unlike InGaAs, InGaAlBiAs offers enough freedom for band engineering to have a material compatible with a 1550 nm pump and a Fermi level deep in the bandgap, meaning low carrier concentration and high dark resistivity. Band engineering is possible by incorporating aluminum to lift the conduction band edge to the Fermi level and bismuth to keep a bandgap compatible with 1550 nm excitation.Item Determining the band alignment of TbAs:GaAs and TbAs:In0.53Ga0.47As(American Institute of Physics, 2015-09-10) Bomberger, Cory C.; Vanderhoef, Laura R.; Rahman, Abdur; Shah, Deesha; Chase, D. Bruce; Taylor, Antoinette J.; Azad, Abul K.; Doty, Matthew F.; Zide, Joshua M. O.; Cory C. Bomberger, Laura R. Vanderhoef, Abdur Rahman, Deesha Shah, D. Bruce Chase, Antoinette J. Taylor, Abul K. Azad, Matthew F. Doty, and Joshua M. O. Zide; Bomberger, Cory C.; Vanderhoef, Laura R.; Chase, D. Bruce; Doty, Matthew F.; Zide, Joshua M. O.We propose and systematically justify a band structure for TbAs nanoparticles in GaAs and In0.53Ga0.47As host matrices. Fluence-dependent optical-pump terahertz-probe measurements suggest the TbAs nanoparticles have a band gap and provide information on the carrier dynamics, which are determined by the band alignment. Spectrophotometry measurements provide the energy of optical transitions in the nanocomposite systems and reveal a large blue shift in the absorption energy when the host matrix is changed from In0.53Ga0.47As to GaAs. Finally, Hall data provides the approximate Fermi level in each system. From this data, we deduce that the TbAs:GaAs system forms a type I (straddling) heterojunction and the TbAs:In0.53Ga0.47As system forms a type II (staggered) heterojunction.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.