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Open Access Publications from the University of California

Scholarly Works (5 results)

  • Thesis
  • Peer Reviewed
UC Berkeley Electronic Theses and Dissertations (2011)

Abstract

"Physics of Optoelectronic and Plasmonic Devices: Cavities, Waveguides, Modulators and Lasers"

By

Volker Jendrik Sorger

Doctor of Philosophy in Engineering-Mechanical Engineering

And the Designated Emphasis In

Nanoscale Science and Engineering

University of California, Berkeley

Professor Xiang Zhang, Chair

This dissertation explores the fundamental interactions between light and matter towards devices applications in the field of Opto-electronics and metal-optics, or plasmonics. In its core, this dissertation attempts, and succeeds to demonstrate strong enhancements of such interactions. Here, surface plasmon polaritons, collective electronic oscillations at metal-dielectric interfaces, play a significant role, as they allow for nano-scale wavelengths with visible and near-infrared light. In particular the rate of spontaneous emission was shown to be significantly increased via increasing the local electromagnetic field density surrounding a photonic emitter. A nanoscale plasmonic cavity has been fabricated and shown to provide reasonable feedback while confining the optical mode beyond the diffraction limit of light. In addition microcavities cavities were coated with metal demonstrating the highest cavity quality-factor for a plasmonic system to date.

Furthermore, a low loss deep-subwavelength waveguide has been proposed and experimentally demonstrated. This novel waveguide uniquely combines ultra-small squeezed optical propagating fields with semiconductor technology, allowing for high waveguiding figure-of-merits; wave propagation versus mode confinement. Deploying near-field scanning optical microscopy, the tiny optical mode of such waveguides has been probed, revealing the first images of truly nanoscale optical waveguiding.

The challenge to demonstrate a sub-wavelength plasmon Nanolaser was successfully overcome by deploying the aforementioned hybrid plasmonic waveguide architecture. Such Nanolasers were found to operate close to the thresholdless, ideal regime for lasers. The high optical loss of such plasmon Nanolasers was mitigated by utilizing the unique physical mechanism inside the plasmon Nanolaser cavity. In particular, this dissertation shows, that ultra-small optical modes are enhancing laser-mode selection leading to higher laser efficiencies and potentially reduced laser thresholds. Furthermore, this study of plasmon Nanolasers suggests a direct laser modulation bandwidth far exceeding that of any traditional laser and lastly discusses the integration of coherent nanoscale light source into ultra-compact integrated photonic on-chip solutions.

Enhanced light-matter-interactions have further been explored towards combining photonic and logic, or computation. Here, plasmonic-optically enhanced architectures were used to create optical non-linear effects with unprecedented efficiency and ultra-small device foot-prints. In particular, the electro-optical effect was deployed in a novel device interfacing silicon-on-insulator technology with hybrid plasmonics. First results show that one to two volt of electrical bias can switch an optical signal requiring only a few micrometer-long light-matter-interaction lengths. Furthermore, higher order non-linear effects, e.g. 3rd order, have been predicted to boost such interactions even further paving the way towards efficient nanoscale all-optical transistors and routers.

Light-emitting tunnel junctions on the basis of metal-insulator-semiconductors were realized showing the highest quantum efficiency for such devices to date. Such 100% CMOS compatible on-chip silicon-based light sources were simulated yielding direct modulation speeds far exceeding the tea-hertz range.

In conclusion Opto-electronic device physics has been explored on a fundamental level towards enhancing light matter interactions. On this basis, novel nanophotonics building blocks have been realized and found to potentially out-perform traditional pure electronic or photonic devices. These findings are of importance towards fueling the global exponentially growing demand for data-bandwidth and novel functionalities such as sensing and bio-medical applications as well as ultrafast on-chip photonics. Especially with the raising energy consumption of information technology, nanoscale integrated hybrid circuits not only hold promise to deliver higher performance but also energy concise solutions due to enhanced physical effects.

 

    Cover page: Physics of Optoelectronic and Plasmonic Devices: Cavities, Waveguides, Modulators and Lasers
    • Article
    • Peer Reviewed
    UC Berkeley Previously Published Works (2016)
    For decades, progress in the field of optical (including solar) energy conversion was dominated by advances in the conventional concentrating optics and materials design. In recent years, however, conceptual and technological breakthroughs in the fields of nanophotonics and plasmonics combined with a better understanding of the thermodynamics of the photon energy-conversion processes reshaped the landscape of energy-conversion schemes and devices. Nanostructured devices and materials that make use of size quantization effects to manipulate photon density of states offer a way to overcome the conventional light absorption limits. Novel optical spectrum splitting and photon-recycling schemes reduce the entropy production in the optical energy-conversion platforms and boost their efficiencies. Optical design concepts are rapidly expanding into the infrared energy band, offering new approaches to harvest waste heat, to reduce the thermal emission losses, and to achieve noncontact radiative cooling of solar cells as well as of optical and electronic circuitries. Light-matter interaction enabled by nanophotonics and plasmonics underlie the performance of the third- and fourth-generation energy-conversion devices, including up- and down-conversion of photon energy, near-field radiative energy transfer, and hot electron generation and harvesting. Finally, the increased market penetration of alternative solar energy-conversion technologies amplifies the role of cost-driven and environmental considerations. This roadmap on optical energy conversion provides a snapshot of the state of the art in optical energy conversion, remaining challenges, and most promising approaches to address these challenges. Leading experts authored 19 focused short sections of the roadmap where they share their vision on a specific aspect of this burgeoning research field. The roadmap opens up with a tutorial section, which introduces major concepts and terminology. It is our hope that the roadmap will serve as an important resource for the scientific community, new generations of researchers, funding agencies, industry experts, and investors.
      Cover page: Roadmap on optical energy conversion
      • Article
      • Peer Reviewed
      UCLA Previously Published Works (2020)
      Chiral degrees of freedom occur in matter and in electromagnetic fields and constitute an area of research that is experiencing renewed interest driven by recent observations of the chiral-induced spin selectivity (CISS) effect in chiral molecules and engineered nanomaterials. The CISS effect underpins the fact that charge transport through nanoscopic chiral structures favors a particular electronic spin orientation, resulting in large room-temperature spin polarizations. Observations of the CISS effect suggest opportunities for spin control and for the design and fabrication of room-temperature quantum devices from the bottom up, with atomic-scale precision. Any technology that relies on optimal charge transport, including quantum devices for logic, sensing, and storage, may benefit from chiral quantum properties. These properties can be theoretically and experimentally investigated from a quantum information perspective, which is presently lacking. There are uncharted implications for the quantum sciences once chiral couplings can be engineered to control the storage, transduction, and manipulation of quantum information. This forward-looking perspective provides a survey of the experimental and theoretical fundamentals of chiral-influenced quantum effects, and presents a vision for their future roles in enabling room-temperature quantum technologies.
        Cover page: A Chirality-Based Quantum Leap
        • Article
        • Peer Reviewed
        UC Davis Previously Published Works (2021)
        Integrated photonics is at the heart of many classical technologies, from optical communications to biosensors, LIDAR, and data center fiber interconnects. There is strong evidence that these integrated technologies will play a key role in quantum systems as they grow from few-qubit prototypes to tens of thousands of qubits. The underlying laser and optical quantum technologies, with the required functionality and performance, can only be realized through the integration of these components onto quantum photonic integrated circuits (QPICs) with accompanying electronics. In the last decade, remarkable advances in quantum photonic integration and a dramatic reduction in optical losses have enabled benchtop experiments to be scaled down to prototype chips with improvements in efficiency, robustness, and key performance metrics. The reduction in size, weight, power, and improvement in stability that will be enabled by QPICs will play a key role in increasing the degree of complexity and scale in quantum demonstrations. In the next decade, with sustained research, development, and investment in the quantum photonic ecosystem (i.e. PIC-based platforms, devices and circuits, fabrication and integration processes, packaging, and testing and benchmarking), we will witness the transition from single- and few-function prototypes to the large-scale integration of multi-functional and reconfigurable QPICs that will define how information is processed, stored, transmitted, and utilized for quantum computing, communications, metrology, and sensing. This roadmap highlights the current progress in the field of integrated quantum photonics, future challenges, and advances in science and technology needed to meet these challenges.
          Cover page: Roadmap on Integrated Quantum Photonics
          • Article
          • Peer Reviewed
          UCLA Previously Published Works (2022)
          There is increasing interest in the study of chiral degrees of freedom occurring in matter and in electromagnetic fields. Opportunities in quantum sciences will likely exploit two main areas that are the focus of this Review: (1) recent observations of the chiral-induced spin selectivity (CISS) effect in chiral molecules and engineered nanomaterials and (2) rapidly evolving nanophotonic strategies designed to amplify chiral light-matter interactions. On the one hand, the CISS effect underpins the observation that charge transport through nanoscopic chiral structures favors a particular electronic spin orientation, resulting in large room-temperature spin polarizations. Observations of the CISS effect suggest opportunities for spin control and for the design and fabrication of room-temperature quantum devices from the bottom up, with atomic-scale precision and molecular modularity. On the other hand, chiral-optical effects that depend on both spin- and orbital-angular momentum of photons could offer key advantages in all-optical and quantum information technologies. In particular, amplification of these chiral light-matter interactions using rationally designed plasmonic and dielectric nanomaterials provide approaches to manipulate light intensity, polarization, and phase in confined nanoscale geometries. Any technology that relies on optimal charge transport, or optical control and readout, including quantum devices for logic, sensing, and storage, may benefit from chiral quantum properties. These properties can be theoretically and experimentally investigated from a quantum information perspective, which has not yet been fully developed. There are uncharted implications for the quantum sciences once chiral couplings can be engineered to control the storage, transduction, and manipulation of quantum information. This forward-looking Review provides a survey of the experimental and theoretical fundamentals of chiral-influenced quantum effects and presents a vision for their possible future roles in enabling room-temperature quantum technologies.
            Cover page: A Chirality-Based Quantum Leap
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