Recursos de colección

Caltech Authors (157.532 recursos)

Repository of works by Caltech published authors.

Group = Kavli Nanoscience Institute

Mostrando recursos 1 - 20 de 124

  1. 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.

  2. 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....

  3. 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...

  4. 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...

  5. 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...

  6. 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...

  7. Complex wavefront engineering with disorder-engineered metasurfaces

    Jang, Mooseok; Horie, Yu; Shibukawa, Atsushi; Brake, Joshua; Liu, Yan; Kamali, Seyedeh Mahsa; Arbabi, Amir; Ruan, Haowen; Faraon, Andrei; Yang, Changhuei
    Recently, complex wavefront engineering with disordered media has demonstrated optical manipulation capabilities beyond those of conventional optics. These capabilities include extended volume, aberration-free focusing and subwavelength focusing via evanescent mode coupling. However, translating these capabilities to useful applications has remained challenging as the input-output characteristics of the disordered media (P variables) need to be exhaustively determined via O(P) measurements. Here, we propose a paradigm shift where the disorder is specifically designed so that its exact characteristics are known, resulting in an a priori determined transmission matrix that can be utilized with only a few alignment steps. We implement this concept...

  8. The Phonon-Limited-Linewidth of Brillouin Lasers at Cryogenic Temperatures

    Suh, Myoung-Gyun; Yang, Qi-Fan; Vahala, Kerry J.
    Laser linewidth is of central importance in spectroscopy, frequency metrology and all applications of lasers requiring high coherence. It is also of fundamental importance, because the Schawlow-Townes laser linewidth limit is of quantum origin. Recently, a theory of stimulated Brillouin laser (SBL) linewidth has been reported. While the SBL linewidth formula exhibits power and optical Q factor dependences that are identical to the Schawlow-Townes formula, a source of noise not present in two-level lasers, phonon occupancy of the Brillouin mechanical mode, is predicted to be the dominant SBL linewidth contribution. Moreover, the quantum-limit of the SBL linewidth is predicted to be...

  9. Phonon-Limited-Linewidth of Brillouin Lasers at Cryogenic Temperatures

    Suh, Myoung-Gyun; Yang, Qi-Fan; Vahala, Kerry J.
    Laser linewidth is of central importance in spectroscopy, frequency metrology, and all applications of lasers requiring high coherence. It is also of fundamental importance, because the Schawlow-Townes laser linewidth limit is of quantum origin. Recently, a theory of stimulated Brillouin laser (SBL) linewidth has been reported. While the SBL linewidth formula exhibits power and optical Q factor dependences that are identical to the Schawlow-Townes formula, a source of noise not present in conventional lasers, phonon occupancy of the Brillouin mechanical mode is predicted to be the dominant SBL linewidth contribution. Moreover, the quantum limit of the SBL linewidth is predicted...

  10. Submicrometer Dimple Array Based Interference Color Field Displays and Sensors

    Lezec, H. J.; McMahon, J. J.; Nalamasu, O.; Ajayan, P. M.
    We report a technique for producing bright color fields over extended surfaces, via optical interference, with the capability of producing arbitrary visible colors in areas as small as 100 μm^2. Periodic arrays of submicrometer dimples are fabricated on reflective silicon surfaces, and diffraction-induced mutual interference of light reflected from the upper and lower levels of the dimpled surfaces generates color depending on wavelength scaled dimple depth and periodicity. Colors of the entire visible spectrum can be generated by dimple arrays with different dimple depths. The topological permeability of such an open surface readily allows infusion of liquids, with different refractive...

  11. Towards visible soliton microcomb generation

    Lee, Seung Hoon; Oh, Dong Yoon; Yang, Qi-Fan; Shen, Boqiang; Wang, Heming; Yang, Ki Youl; Lai, Yu Hung; Yi, Xu; Vahala, Kerry
    Frequency combs have applications that extend from the ultra-violet into the mid infrared bands. Microcombs, a miniature and often semiconductor-chip-based device, can potentially access most of these applications, but are currently more limited in spectral reach. Here, we demonstrate mode-locked silica microcombs with emission near the edge of the visible spectrum. By using both geometrical and mode-hybridization dispersion control, devices are engineered for soliton generation while also maintaining optical Q factors as high as 80 million. Electronics-bandwidth-compatible (20 GHz) soliton mode locking is achieved with threshold powers as low as 5.4 mW. These are the shortest wavelength soliton microcombs demonstrated...

  12. Mechanical On-Chip Microwave Circulator

    Barzanjeh, S.; Wulf, M.; Peruzzo, M.; Kalaee, M.; Dieterle, P. B.; Painter, O.; Fink, J. M.
    Nonreciprocal circuit elements form an integral part of modern measurement and communication systems. Mathematically they require breaking of time-reversal symmetry, typically achieved using magnetic materials and more recently using the quantum Hall effect, parametric permittivity modulation or Josephson nonlinearities. Here, we demonstrate an on-chip magnetic-free circulator based on reservoir engineered optomechanical interactions. Directional circulation is achieved with controlled phase-sensitive interference of six distinct electro-mechanical signal conversion paths. The presented circulator is compact, its silicon-on-insulator platform is compatible with both superconducting qubits and silicon photonics, and its noise performance is close to the quantum limit. With a high dynamic range, a tunable bandwidth of up to 30 MHz and an in-situ reconfigurability...

  13. Fabrication of Single Crystal Gallium Phosphide Thin Films on Glass

    Emmer, Hal; Chen, Christopher T.; Saive, Rebecca; Friedrich, Dennis; Horie, Yu; Arbabi, Amir; Faraon, Andrei; Atwater, Harry A.
    Due to its high refractive index and low absorption coefficient, gallium phosphide is an ideal material for photonic structures targeted at the visible wavelengths. However, these properties are only realized with high quality epitaxial growth, which limits substrate choice and thus possible photonic applications. In this work, we report the fabrication of single crystal gallium phosphide thin films on transparent glass substrates via transfer bonding. GaP thin films on Si (001) and (112) grown by MOCVD are bonded to glass, and then the growth substrate is removed with a XeF_2 vapor etch. The resulting GaP films have surface roughnesses below...

  14. Integrated Ultra-High-Q Optical Resonator

    Yang, Ki Youl; Oh, Dong Yoon; Lee, Seung Hoon; Yang, Qi-Fan; Yi, Xu; Vahala, Kerry
    Optical microcavities are compact, often chip-based devices, that are essential in technologies spanning frequency metrology to biosensing. They have also enabled new science in quantum information and cavity optomechanics. Performance requirements in subjects like cavity-QED and sensing have long placed emphasis on low-optical-loss (high-Q-factor) micrometer-scale resonators. However, an array of system-on-a-chip applications have emerged that also require millimeter-scale devices. To avoid impractically-high pumping powers associated with the increased stored energy of these larger devices, Q factors well above those possible in existing integrable resonators are needed. Here, we demonstrate a silicon-chip-based microcavity that combines high-Q performance with monolithic integration. Q...

  15. High Photovoltaic Quantum Efficiency in Ultrathin van der Waals Heterostructures

    Wong, Joeson; Jariwala, Deep; Tagliabue, Giulia; Tat, Kevin; Davoyan, Artur R.; Sherrott, Michelle C.; Atwater, Harry A.
    We report experimental measurements for ultrathin (<15 nm) van der Waals heterostructures exhibiting external quantum efficiencies exceeding 50% and show that these structures can achieve experimental absorbance >90%. By coupling electromagnetic simulations and experimental measurements, we show that pn Wse_2/MoS_2 heterojunctions with vertical carrier collection can have internal photocarrier collection efficiencies exceeding 70%.

  16. Counter-propagating solitons in microresonators

    Yang, Qi-Fan; Yi, Xu; Yang, Ki Youl; Vahala, Kerry
    Solitons occur in many physical systems when a nonlinearity compensates wave dispersion. Their recently demonstrated formation in microresonators has opened a new research direction for nonlinear optical physics. Soliton mode locking also endows frequency microcombs with the enhanced stability necessary for miniaturization of spectroscopy and frequency metrology systems. These microresonator solitons orbit around a closed waveguide path and produce a repetitive output pulse stream at a rate set by the roundtrip time. Here, counter-propagating solitons that simultaneously orbit in an opposing sense (clockwise/counter-clockwise) are studied. Despite sharing the same spatial mode family, their roundtrip times can be precisely and independently...

  17. Counter-propagating solitons in microresonators

    Yang, Qi-Fan; Yi, Xu; Yang, Ki Youl; Vahala, Kerry
    Solitons occur in many physical systems when a nonlinearity compensates wave dispersion. Their recently demonstrated formation in microresonators has opened a new research direction for nonlinear optical physics. Soliton mode locking also endows frequency microcombs with the enhanced stability necessary for miniaturization of spectroscopy and frequency metrology systems. These microresonator solitons orbit around a closed waveguide path and produce a repetitive output pulse stream at a rate set by the roundtrip time. Here, counter-propagating solitons that simultaneously orbit in an opposing sense (clockwise/counter-clockwise) are studied. Despite sharing the same spatial mode family, their roundtrip times can be precisely and independently...

  18. Controlling the sign of chromatic dispersion in diffractive optics

    Arbabi, Ehsan; Arbabi, Amir; Kamali, Seyedeh Mahsa; Horie, Yu; Faraon, Andrei
    Diffraction gratings disperse light in a rainbow of colors with the opposite order than refractive prisms, a phenomenon known as negative dispersion [1, 2]. While refractive dispersion can be controlled via material refractive index, diffractive dispersion is fundamentally an interference effect dictated by geometry. Here we show that this fundamental property can be altered using dielectric metasurfaces [3-5], and we experimentally demonstrate diffractive gratings and focusing mirrors with positive, zero, and hyper negative dispersion. These optical elements are implemented using a reflective metasurface composed of dielectric nano-posts that provide simultaneous control over phase and its wavelength derivative. In addition, as...

  19. Planar Metasurface Retroreflector

    Arbabi, Amir; Arbabi, Ehsan; Horie, Yu; Kamali, Seyedeh Mahsa; Faraon, Andrei
    Metasurfaces are two-dimensional arrangements of subwavelength scatterers that control the propagation of optical waves. Here, we show that cascaded metasurfaces, each performing a predefined mathematical transformation, provide a new optical design framework that enables new functionalities not yet demonstrated with single metasurfaces. Specifically, we demonstrate that retroreflection can be achieved with two vertically stacked planar metasurfaces, the first performing a spatial Fourier transform and its inverse, and the second imparting a spatially varying momentum to the Fourier transform of the incident light. Using this concept, we fabricate and test a planar monolithic near-infrared retroreflector composed of two layers of silicon...

  20. Atomic-scale Structural and Chemical Characterization of Hexagonal Boron Nitride Layers Synthesized at the Wafer-Scale with Monolayer Thickness Control

    Lin, Wei-Hsiang; Brar, Victor W.; Jariwala, Deep; Sherrott, Michelle C.; Tseng, Wei-Shiuan; Wu, Chih-I; Yeh, Nai-Chang; Atwater, Harry A.
    Hexagonal boron nitride (h-BN) is a promising two-dimensional insulator with a large band gap and low density of charged impurities that is isostructural and isoelectronic with graphene. Here we report the chemical and atomic-scale structure of CVD-grown wafer-scale (∼25 cm^2) h-BN sheets ranging in thickness from 1 to 20 monolayers. Atomic-scale images of h-BN on Au and graphene/Au substrates obtained by scanning tunneling microscopy reveal high h-BN crystalline quality in monolayer samples. Further characterization of 1–20 monolayer samples indicates uniform thickness for wafer-scale areas; this thickness control is a result of precise control of the precursor flow rate, deposition temperature...

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