{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/100417"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/100417","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Reducing extrinsic damping of surface acoustic waves at gigahertz frequencies","abstract":"High-frequency surface acoustic waves (SAWs) in the GHz range can be generated using absorption from an ultrafast laser in a patterned metallic grating on a substrate. Reducing the attenuation at these frequencies can yield better sensors as well as enable them to better probe phonon and electron-phonon interactions near surfaces. It is not clear from existing experiments which mechanisms dominate damping at high frequencies. We calculate damping times of SAWs due to various mechanism in the 1-100 GHz range to find that mechanical loading of the grating on the substrate dominates dissipation by radiating energy from the surface into the bulk. To overcome this and enable future measurements to probe intrinsic damping, we propose incorporating distributed acoustic Bragg reflectors (DABRs) in the experimental structure. Layers of alternating materials with contrasting acoustic impedances embedded a wavelength away from the surface serve to reflect energy back to the surface. Using numerical simulations, we show that a single Bragg reflector is sufficient to increase the energy density at the surface by more than five times. We quantify the resulting damping time to find that it is longer than the intrinsic damping time. The proposed structure can enable future measurements of intrinsic damping in SAWs at 100 GHz.","abstract_html":"High-frequency surface acoustic waves (SAWs) in the GHz range can be generated using absorption from an ultrafast laser in a patterned metallic grating on a substrate. Reducing the attenuation at these frequencies can yield better sensors as well as enable them to better probe phonon and electron-phonon interactions near surfaces. It is not clear from existing experiments which mechanisms dominate damping at high frequencies. We calculate damping times of SAWs due to various mechanism in the 1-100 GHz range to find that mechanical loading of the grating on the substrate dominates dissipation by radiating energy from the surface into the bulk. To overcome this and enable future measurements to probe intrinsic damping, we propose incorporating distributed acoustic Bragg reflectors (DABRs) in the experimental structure. Layers of alternating materials with contrasting acoustic impedances embedded a wavelength away from the surface serve to reflect energy back to the surface. Using numerical simulations, we show that a single Bragg reflector is sufficient to increase the energy density at the surface by more than five times. We quantify the resulting damping time to find that it is longer than the intrinsic damping time. The proposed structure can enable future measurements of intrinsic damping in SAWs at 100 GHz.","abstract_has_math":false,"creators":["Gelda, Dhruv"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"M.S.","degree_level":"Thesis","degree_discipline":"Mechanical Engineering","degree_department":null,"school":null,"contributors":["Sinha, Sanjiv"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2018,"date_issued":"2018-08-14T21:37:12Z","date_published":"2018-08-14T21:37:12Z","updated_at":"2026-07-22T22:24:38Z","subjects":["Surface Acoustic Waves, Damping , Bragg Reflectors"],"languages":["en"],"rights":["Copyright 2015 Dhruv Gelda"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/100417","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Sinha, Sanjiv"]},{"key":"dc:creator","label":"Author","values":["Gelda, Dhruv"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2018-08-14T21:37:12Z","2020-08-15T09:15:08Z","2017-01-31","2017-05"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Mechanical Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["M.S."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Surface Acoustic Waves, Damping , Bragg Reflectors"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2015 Dhruv Gelda"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/100417"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["High-frequency surface acoustic waves (SAWs) in the GHz range can be generated using absorption from an ultrafast laser in a patterned metallic grating on a substrate. Reducing the attenuation at these frequencies can yield better sensors as well as enable them to better probe phonon and electron-phonon interactions near surfaces. It is not clear from existing experiments which mechanisms dominate damping at high frequencies. We calculate damping times of SAWs due to various mechanism in the 1-100 GHz range to find that mechanical loading of the grating on the substrate dominates dissipation by radiating energy from the surface into the bulk. To overcome this and enable future measurements to probe intrinsic damping, we propose incorporating distributed acoustic Bragg reflectors (DABRs) in the experimental structure. Layers of alternating materials with contrasting acoustic impedances embedded a wavelength away from the surface serve to reflect energy back to the surface. Using numerical simulations, we show that a single Bragg reflector is sufficient to increase the energy density at the surface by more than five times. We quantify the resulting damping time to find that it is longer than the intrinsic damping time. The proposed structure can enable future measurements of intrinsic damping in SAWs at 100 GHz.","Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2019-05-01","The student, Dhruv Gelda, accepted the attached license on 2017-01-31 at 12:44.","The student, Dhruv Gelda, submitted this Thesis for approval on 2017-01-31 at 13:04.","This Thesis was approved for publication on 2017-01-31 at 15:56.","DSpace SAF Submission Ingestion Package generated from Vireo submission #10551 on 2018-08-14 at 16:00:20","Made available in DSpace on 2018-08-14T21:37:12Z (GMT). No. of bitstreams: 3 GELDA-THESIS-2017.pdf: 1627807 bytes, checksum: d2db1fece368d55f4c7cd6c68ade1015 (MD5) ms-thesis.zip: 1174432 bytes, checksum: 85756d0c6ac00dd63298d6d4de266519 (MD5) LICENSE.txt: 4208 bytes, checksum: 6ad8902a8d3519e4dd0628838dd0a973 (MD5) Previous issue date: 2017-01-31","Embargo set by: Seth Robbins for item 106497 Lift date: 2020-08-14T21:37:20Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system","Limited Restriction Lifted for Item 106497 on 2020-08-15T09:15:08Z."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Reducing extrinsic damping of surface acoustic waves at gigahertz frequencies"]}]}],"canonical_facts":{"dc:contributor":["Sinha, Sanjiv"],"dc:creator":["Gelda, Dhruv"],"dc:date":["2018-08-14T21:37:12Z","2020-08-15T09:15:08Z","2017-01-31","2017-05"],"dc:description":["High-frequency surface acoustic waves (SAWs) in the GHz range can be generated using absorption from an ultrafast laser in a patterned metallic grating on a substrate. Reducing the attenuation at these frequencies can yield better sensors as well as enable them to better probe phonon and electron-phonon interactions near surfaces. It is not clear from existing experiments which mechanisms dominate damping at high frequencies. We calculate damping times of SAWs due to various mechanism in the 1-100 GHz range to find that mechanical loading of the grating on the substrate dominates dissipation by radiating energy from the surface into the bulk. To overcome this and enable future measurements to probe intrinsic damping, we propose incorporating distributed acoustic Bragg reflectors (DABRs) in the experimental structure. Layers of alternating materials with contrasting acoustic impedances embedded a wavelength away from the surface serve to reflect energy back to the surface. Using numerical simulations, we show that a single Bragg reflector is sufficient to increase the energy density at the surface by more than five times. We quantify the resulting damping time to find that it is longer than the intrinsic damping time. The proposed structure can enable future measurements of intrinsic damping in SAWs at 100 GHz.","Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2019-05-01","The student, Dhruv Gelda, accepted the attached license on 2017-01-31 at 12:44.","The student, Dhruv Gelda, submitted this Thesis for approval on 2017-01-31 at 13:04.","This Thesis was approved for publication on 2017-01-31 at 15:56.","DSpace SAF Submission Ingestion Package generated from Vireo submission #10551 on 2018-08-14 at 16:00:20","Made available in DSpace on 2018-08-14T21:37:12Z (GMT). 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