Recursos de colección

Caltech Authors (160.918 recursos)

Repository of works by Caltech published authors.

Group = Kavli Nanoscience Institute

Mostrando recursos 1 - 20 de 229

  1. Dynamically controlled Purcell enhancement of visible spontaneous emission in a gated plasmonic heterostructure

    Lu, Yu-Jung; Sokhoyan, Ruzan; Cheng, Wen-Hui; Shirmanesh, Ghazaleh Kafaie; Davoyan, Artur R.; Pala, Ragip A.; Thyagarajan, Krishnan; Atwater, Harry A.
    Emission control of colloidal quantum dots (QDs) is a cornerstone of modern high-quality lighting and display technologies. Dynamic emission control of colloidal QDs in an optoelectronic device is usually achieved by changing the optical pump intensity or injection current density. Here we propose and demonstrate a distinctly different mechanism for the temporal modulation of QD emission intensity at constant optical pumping rate. Our mechanism is based on the electrically controlled modulation of the local density of optical states (LDOS) at the position of the QDs, resulting in the modulation of the QD spontaneous emission rate, far-field emission intensity, and quantum...

  2. Dynamically controlled Purcell enhancement of visible spontaneous emission in a gated plasmonic heterostructure

    Lu, Yu-Jung; Sokhoyan, Ruzan; Cheng, Wen-Hui; Shirmanesh, Ghazaleh Kafaie; Davoyan, Artur R.; Pala, Ragip A.; Thyagarajan, Krishnan; Atwater, Harry A.
    Emission control of colloidal quantum dots (QDs) is a cornerstone of modern high-quality lighting and display technologies. Dynamic emission control of colloidal QDs in an optoelectronic device is usually achieved by changing the optical pump intensity or injection current density. Here we propose and demonstrate a distinctly different mechanism for the temporal modulation of QD emission intensity at constant optical pumping rate. Our mechanism is based on the electrically controlled modulation of the local density of optical states (LDOS) at the position of the QDs, resulting in the modulation of the QD spontaneous emission rate, far-field emission intensity, and quantum...

  3. Shock Synthesis of Five-component Icosahedral Quasicrystals

    Oppenheim, Julius; Ma, Chi; Hu, Jinping; Bindi, Luca; Steinhardt, Paul J.; Asimow, Paul D.
    Five-component icosahedral quasicrystals with compositions in the range Al_(68–73)Fe_(11–16)Cu_(10–12)Cr_(1–4)Ni_(1–2) were recently recovered after shocking metallic CuAl_5 and (Mg_(0.75)Fe_(0.25))_2SiO_4 olivine in a stainless steel 304 chamber, intended to replicate a natural shock that affected the Khatyrka meteorite. The iron in those quasicrystals might have originated either from reduction of Fe^(2+) in olivine or from the stainless steel chamber. In this study, we clarify the shock synthesis mechanism of icosahedral quasicrystals through two new shock recovery experiments. When CuAl_5 and Fe^(2+)-bearing olivine were isolated in a Ta capsule, no quasicrystals were found. However, with only metallic starting materials, numerous micron-sized five-component icosahedral...

  4. Shock Synthesis of Five-component Icosahedral Quasicrystals

    Oppenheim, Julius; Ma, Chi; Hu, Jinping; Bindi, Luca; Steinhardt, Paul J.; Asimow, Paul D.
    Five-component icosahedral quasicrystals with compositions in the range Al_(68–73)Fe_(11–16)Cu_(10–12)Cr_(1–4)Ni_(1–2) were recently recovered after shocking metallic CuAl_5 and (Mg_(0.75)Fe_(0.25))_2SiO_4 olivine in a stainless steel 304 chamber, intended to replicate a natural shock that affected the Khatyrka meteorite. The iron in those quasicrystals might have originated either from reduction of Fe^(2+) in olivine or from the stainless steel chamber. In this study, we clarify the shock synthesis mechanism of icosahedral quasicrystals through two new shock recovery experiments. When CuAl_5 and Fe^(2+)-bearing olivine were isolated in a Ta capsule, no quasicrystals were found. However, with only metallic starting materials, numerous micron-sized five-component icosahedral...

  5. Shock Synthesis of Decagonal Quasicrystals

    Oppenheimer, J.; Ma, C.; Hu, J.; Bindi, L.; Steinhardt, P. J.; Asimow, P. D.
    The Khatyrka meteorite contains both icosahedral and decagonal quasicrystals. In our previous studies, icosahedral quasicrystals have been synthesized and recovered from shock experiments at the interface between CuAl_5 and stainless steel 304 alloys. In this study, we report a new shock recovery experiment aimed at synthesizing decagonal quasicrystals similar to decagonite, natural Al_(71)Ni_(24)Fe_5. Aluminum 2024 and permalloy 80 alloys were stacked together and shocked in a stainless steel 304 recovery chamber. Abundant decagonal quasicrystals of average composition Al_(73)Ni_(19)Fe_4Cu_2Mg_(0.6)Mo_(0.4)Mn_(0.3) with traces of Si and Cr were found along the recovered interface between the Al and permalloy. The experiment also synthesized AlNiFe...

  6. Shock Synthesis of Decagonal Quasicrystals

    Oppenheim, J.; Ma, C.; Hu, J.; Bindi, L.; Steinhardt, P. J.; Asimow, P. D.
    The Khatyrka meteorite contains both icosahedral and decagonal quasicrystals. In our previous studies, icosahedral quasicrystals have been synthesized and recovered from shock experiments at the interface between CuAl_5 and stainless steel 304 alloys. In this study, we report a new shock recovery experiment aimed at synthesizing decagonal quasicrystals similar to decagonite, natural Al_(71)Ni_(24)Fe_5. Aluminum 2024 and permalloy 80 alloys were stacked together and shocked in a stainless steel 304 recovery chamber. Abundant decagonal quasicrystals of average composition Al_(73)Ni_(19)Fe_4Cu_2Mg_(0.6)Mo_(0.4)Mn_(0.3) with traces of Si and Cr were found along the recovered interface between the Al and permalloy. The experiment also synthesized AlNiFe...

  7. Shock Synthesis of Decagonal Quasicrystals

    Oppenheim, J.; Ma, C.; Hu, J.; Bindi, L.; Steinhardt, P. J.; Asimow, P. D.
    The Khatyrka meteorite contains both icosahedral and decagonal quasicrystals. In our previous studies, icosahedral quasicrystals have been synthesized and recovered from shock experiments at the interface between CuAl_5 and stainless steel 304 alloys. In this study, we report a new shock recovery experiment aimed at synthesizing decagonal quasicrystals similar to decagonite, natural Al_(71)Ni_(24)Fe_5. Aluminum 2024 and permalloy 80 alloys were stacked together and shocked in a stainless steel 304 recovery chamber. Abundant decagonal quasicrystals of average composition Al_(73)Ni_(19)Fe_4Cu_2Mg_(0.6)Mo_(0.4)Mn_(0.3) with traces of Si and Cr were found along the recovered interface between the Al and permalloy. The experiment also synthesized AlNiFe...

  8. Shock Synthesis of Decagonal Quasicrystals

    Oppenheim, J.; Ma, C.; Hu, J.; Bindi, L.; Steinhardt, P. J.; Asimow, P. D.
    The Khatyrka meteorite contains both icosahedral and decagonal quasicrystals. In our previous studies, icosahedral quasicrystals have been synthesized and recovered from shock experiments at the interface between CuAl_5 and stainless steel 304 alloys. In this study, we report a new shock recovery experiment aimed at synthesizing decagonal quasicrystals similar to decagonite, natural Al_(71)Ni_(24)Fe_5. Aluminum 2024 and permalloy 80 alloys were stacked together and shocked in a stainless steel 304 recovery chamber. Abundant decagonal quasicrystals of average composition Al_(73)Ni_(19)Fe_4Cu_2Mg_(0.6)Mo_(0.4)Mn_(0.3) with traces of Si and Cr were found along the recovered interface between the Al and permalloy. The experiment also synthesized AlNiFe...

  9. High-speed, phase-dominant spatial light modulation with silicon-based active resonant antennas

    Horie, Yu; Arbabi, Amir; Arbabi, Ehsan; Kamali, Seyedeh Mahsa; Faraon, Andrei
    Spatiotemporal control of optical wavefronts is of great importance in numerous free-space optical applications including imaging in 3D and through scattering media, remote sensing, and generation of various beam profiles for microscopy. Progress in these applications is currently limited due to lack of compact and high-speed spatial light modulators. Here we report an ac- tive antenna comprising a free-space coupled asymmetric Fabry–Perot resonator, that produces a phase-dominant thermo-optic modulation of reflected light at frequencies approaching tens of kilohertz. As a proof of concept for spatial light modulation, we demonstrate a 6×6 array of such active antennas with beam deflection capability....

  10. Van der Waals Materials for Atomically-Thin Photovoltaics: Promise and Outlook

    Jariwala, Deep; Davoyan, Artur R.; Wong, Joeson; Atwater, Harry A.
    Two-dimensional (2D) semiconductors provide a unique opportunity for optoelectronics due to their layered atomic structure, electronic and optical properties. To date, a majority of the application-oriented research in this field has been focused on field-effect electronics as well as photodetectors and light emitting diodes. Here we present a perspective on the use of 2D semiconductors for photovoltaic applications. We discuss photonic device designs that enable light trapping in nanometer-thickness absorber layers, and we also outline schemes for efficient carrier transport and collection. We further provide theoretical estimates of efficiency indicating that 2D semiconductors can indeed be competitive with and complementary...

  11. Hot Carrier Dynamics in Photoexcited Gold Nanostructures: Role of Interband Excitations and Evidence for Ballistic Transport

    Tagliabue, Giulia; Jermyn, Adam S.; Sundararaman, Ravishankar; Welch, Alex J.; DuChene, Joseph S.; Davoyan, Artur R.; Narang, Prineha; Atwater, Harry A.
    Harnessing short-lived photoexcited electron-hole pairs in metal nanostructures has the potential to define a new phase of optoelectronics, enabling control of athermal mechanisms for light harvesting, photodetection and photocatalysis. To date, however, the spatiotemporal dynamics and transport of these photoexcited carriers have been only qualitatively characterized. Plasmon excitation has been widely viewed as an efficient mechanism for generating non-thermal hot carriers. Despite numerous experiments, conclusive evidence elucidating and quantifying the full dynamics of hot carrier generation, transport, and injection has not been reported. Here, we combine experimental measurements with coupled first-principles electronic structure theory and Boltzmann transport calculations to provide...

  12. Hot Carrier Dynamics in Photoexcited Gold Nanostructures: Role of Interband Excitations and Evidence for Ballistic Transport

    Tagliabue, Giulia; Jermyn, Adam S.; Sundararaman, Ravishankar; Welch, Alex J.; DuChene, Joseph S.; Davoyan, Artur R.; Narang, Prineha; Atwater, Harry A.
    Harnessing short-lived photoexcited electron-hole pairs in metal nanostructures has the potential to define a new phase of optoelectronics, enabling control of athermal mechanisms for light harvesting, photodetection and photocatalysis. To date, however, the spatiotemporal dynamics and transport of these photoexcited carriers have been only qualitatively characterized. Plasmon excitation has been widely viewed as an efficient mechanism for generating non-thermal hot carriers. Despite numerous experiments, conclusive evidence elucidating and quantifying the full dynamics of hot carrier generation, transport, and injection has not been reported. Here, we combine experimental measurements with coupled first-principles electronic structure theory and Boltzmann transport calculations to provide...

  13. Hot Carrier Dynamics in Photoexcited Gold Nanostructures: Role of Interband Excitations and Evidence for Ballistic Transport

    Tagliabue, Giulia; Jermyn, Adam S.; Sundararaman, Ravishankar; Welch, Alex J.; DuChene, Joseph S.; Davoyan, Artur R.; Narang, Prineha; Atwater, Harry A.
    Harnessing short-lived photoexcited electron-hole pairs in metal nanostructures has the potential to define a new phase of optoelectronics, enabling control of athermal mechanisms for light harvesting, photodetection and photocatalysis. To date, however, the spatiotemporal dynamics and transport of these photoexcited carriers have been only qualitatively characterized. Plasmon excitation has been widely viewed as an efficient mechanism for generating non-thermal hot carriers. Despite numerous experiments, conclusive evidence elucidating and quantifying the full dynamics of hot carrier generation, transport, and injection has not been reported. Here, we combine experimental measurements with coupled first-principles electronic structure theory and Boltzmann transport calculations to provide...

  14. Tunable optical response and purcell enhancement of gated plasmonic structures

    Sokhoyan, Ruzan; Shirmanesh, Ghazaleh Kafaie; Lu, Yu-Jung; Thyagarajan, Krishnan; Pala, Ragip A.; Atwater, Harry A.
    We experimentally demonstrate plasmonic nanostructures that enable dynamic electrical control of the phase and/or amplitude of the plane wave reflected from the nanostructures. We also demonstrate dynamically controlled Purcell enhancement of spontaneous emission of InP quantum dots (QDs) coupled to plasmonic heterostructures.

  15. Tunable optical response and purcell enhancement of gated plasmonic structures

    Sokhoyan, Ruzan; Shirmanesh, Ghazaleh Kafaie; Lu, Yu-Jung; Thyagarajan, Krishnan; Pala, Ragip A.; Atwater, Harry A.
    We experimentally demonstrate plasmonic nanostructures that enable dynamic electrical control of the phase and/or amplitude of the plane wave reflected from the nanostructures. We also demonstrate dynamically controlled Purcell enhancement of spontaneous emission of InP quantum dots (QDs) coupled to plasmonic heterostructures.

  16. Complex dynamical networks constructed with fully controllable nonlinear nanomechanical oscillators

    Fon, Warren; Matheny, Matthew; Li, Jarvis; Krayzman, Lev; Cross, Michael; D'Souza, Raissa M.; Crutchfield, James; Roukes, Michael Lee
    Control of the global parameters of complex networks has been explored experimentally in a variety of contexts. Yet, the more difficult prospect of realizing arbitrary network architectures, especially analog physical networks, that provide dynamical control of individual nodes and edges has remained elusive. It also proves challenging to measure a complex network’s full internal dynamics given the vast hierarchy of timescales involved. These span from the fastest nodal dynamics to very slow epochs over which emergent global phenomena, including network synchronization and the manifestation of exotic steady states, eventually emerge. Here, we demonstrate an experimental system that satisfies these requirements....

  17. Complex dynamical networks constructed with fully controllable nonlinear nanomechanical oscillators

    Fon, Warren; Matheny, Matthew H.; Li, Jarvis; Krayzman, Lev; Cross, Michael C.; D'Souza, Raissa M.; Crutchfield, James P.; Roukes, Michael L.
    Control of the global parameters of complex networks has been explored experimentally in a variety of contexts. Yet, the more difficult prospect of realizing arbitrary network architectures, especially analog physical networks that provide dynamical control of individual nodes and edges, has remained elusive. Given the vast hierarchy of time scales involved, it also proves challenging to measure a complex network’s full internal dynamics. These span from the fastest nodal dynamics to very slow epochs over which emergent global phenomena, including network synchronization and the manifestation of exotic steady states, eventually emerge. Here, we demonstrate an experimental system that satisfies these...

  18. Nanophotonic rare-earth quantum memory with optically controlled retrieval

    Zhong, Tian; Kindem, Jonathan M.; Bartholomew, John G.; Rochman, Jake; Craiciu, Ioana; Miyazono, Evan; Bettinelli, Marco; Cavalli, Enrico; Verma, Varun; Nam, Sae Woo; Marsili, Francesco; Shaw, Matthew D.; Beyer, Andrew D.; Faraon, Andrei
    Optical quantum memories are essential elements in quantum networks for long distance distribution of quantum entanglement. Scalable development of quantum network nodes requires on-chip qubit storage functionality with control of its readout time. We demonstrate a high-fidelity nanophotonic quantum memory based on a mesoscopic neodymium ensemble coupled to a photonic crystal cavity. The nanocavity enables >95% spin polarization for efficient initialization of the atomic frequency comb memory, and time-bin-selective readout via enhanced optical Stark shift of the comb frequencies. Our solid-state memory is integrable with other chip-scale photon source and detector devices for multiplexed quantum and classical information processing at...

  19. Nanophotonic rare-earth quantum memory with optically controlled retrieval

    Zhong, Tian; Kindem, Jonathan M.; Bartholomew, John G.; Rochman, Jake; Craiciu, Ioana; Miyazono, Evan; Bettinelli, Marco; Cavalli, Enrico; Verma, Varun; Nam, Sae Woo; Marsili, Francesco; Shaw, Matthew D.; Beyer, Andrew D.; Faraon, Andrei
    Optical quantum memories are essential elements in quantum networks for long distance distribution of quantum entanglement. Scalable development of quantum network nodes requires on-chip qubit storage functionality with control of its readout time. We demonstrate a high-fidelity nanophotonic quantum memory based on a mesoscopic neodymium ensemble coupled to a photonic crystal cavity. The nanocavity enables >95% spin polarization for efficient initialization of the atomic frequency comb memory, and time-bin-selective readout via enhanced optical Stark shift of the comb frequencies. Our solid-state memory is integrable with other chip-scale photon source and detector devices for multiplexed quantum and classical information processing at...

  20. Photoelectrochemical Behavior of a Molecular Ru-Based Water-Oxidation Catalyst Bound to TiO_2-Protected Si Photoanodes

    Matheu, Roc; Moreno-Hernandez, Ivan A.; Sala, Xavier; Gray, Harry B.; Brunschwig, Bruce S.; Llobet, Antoni; Lewis, Nathan S.
    A hybrid photoanode based on a molecular water oxidation precatalyst was prepared from TiO_2-protected n- or p+-Si coated with multiwalled carbon nanotubes (CNT) and the ruthenium-based water oxidation precatalyst [Ru^(IV)(tda)(py-pyr)_2(O)], 1(O) (tda^(2–) is [2,2′:6′,2″-terpyridine]-6,6″-dicarboxylato and py-pir is 4-(pyren-1-yl)-N-(pyridin-4-ylmethyl)butanamide). The Ru complex was immobilized by π–π stacking onto CNTs that had been deposited by drop casting onto Si electrodes coated with 60 nm of amorphous TiO_2 and 20 nm of a layer of sputtered C. At pH = 7 with 3 Sun illumination, the n-Si/TiO_2/C/CNT/[1+1(O)] electrodes exhibited current densities of 1 mA cm^(–2) at 1.07 V vs NHE. The current density...

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