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Open Access Publications from the University of California

Scholarly Works (12 results)

  • Thesis
  • Peer Reviewed
UC San Diego Electronic Theses and Dissertations (2018)

Plasmonics is a rapidly growing field of research that has been intensely investigated in the past few decades, for its abundant underlying physics and fruitful practical applications in nanophotonics, integrated optics, optical communication and information processing. Benefiting from the ability to confine light below the diffraction limit and its ultrashort response time (~ 100 fs), a plasmonic-based optical device provides an ideal platform for the study of ultra-strong light-matter interaction and has demonstrated great promise in the strong-coupling quantum system, ultra-fast optical modulators and efficient chip-scale nonlinearities. However, the traditional plasmonic materials and nano-structures suffer from several drawbacks that hinder the further development of plasmonics, such as high optical loss and a limited nonlinear response. As a result, recent plasmonic-based devices have moved towards the quantum regime, searching for the better solution. And many recent reported results show noteworthy achievement. In this thesis, we have demonstrated that an efficient and tunable light source could be realized in delicately fabricated plasmonic nanostructures both in non-resonant and resonant conditions (with the metallic quantum well). It is done by engineering the electron wave-function coupling between plasmonic nanostructures (such as optical nano-antenna), and thus an efficient light generation is reached, which brings on-chip ultrafast and ultra-compact light sources one step closer to reality. In addition, we have shown that the nonlinear susceptibilities of ultra-thin plasmonic films could be engineered to be the state-of-the-art. It is done by introducing the quantum confinement into the plasmonic films (such as Au, Ag or TiN), so that a metallic quantum well is formed, which becomes new building blocks for the more complex plasmonic structures, such as metamaterials. This thesis starts from the theoretical investigation, followed by the nano-fabrication and experimental characterization, ends up with several interesting phenomena, their hidden physics and valuable applications. These quantum plasmonic materials and nano-structures realized in this thesis enable the further integration and functionalization of the plasmonic-based optical devices in the ultra-strong, efficient and fast light-matter interaction regime.

    Cover page: Plasmonics in Quantum region
    • Article
    • Peer Reviewed
    UC San Diego Previously Published Works (2018)
      Cover page: Nonlinear Metasurface Based on Giant Optical Kerr Response of Gold Quantum Wells
      • Article
      • Peer Reviewed
      UC San Diego Previously Published Works (2016)
      With the size of plasmonic devices entering into the nanoscale region, the impact of quantum physics needs to be considered. In the past, the quantum size effect on linear material properties has been studied extensively. However, the nonlinear aspects have not been explored much so far. On the other hand, much effort has been put into the field of integrated nonlinear optics and a medium with large nonlinearity is desirable. Here we study the optical nonlinear properties of a nanometre scale gold quantum well by using the z-scan method and nonlinear spectrum broadening technique. The quantum size effect results in a giant optical Kerr susceptibility, which is four orders of magnitude higher than the intrinsic value of bulk gold and several orders larger than traditional nonlinear media. Such high nonlinearity enables efficient nonlinear interaction within a microscopic footprint, making quantum metallic films a promising candidate for integrated nonlinear optical applications.
        Cover page: Giant Kerr response of ultrathin gold films from quantum size effect
        • Article
        • Peer Reviewed
        UC San Diego Previously Published Works (2016)
        The conventional optical microscope is an inherently two-dimensional (2D) imaging tool. The objective lens, eyepiece and image sensor are all designed to capture light emitted from a 2D 'object plane'. Existing technologies, such as confocal or light sheet fluorescence microscopy have to utilize mechanical scanning, a time-multiplexing process, to capture a 3D image. In this paper, we present a 3D optical microscopy method based upon simultaneously illuminating and detecting multiple focal planes. This is implemented by adding two diffractive optical elements to modify the illumination and detection optics. We demonstrate that the image quality of this technique is comparable to conventional light sheet fluorescent microscopy with the advantage of the simultaneous imaging of multiple axial planes and reduced number of scans required to image the whole sample volume.
          Cover page: Three-dimensional fluorescent microscopy via simultaneous illumination and detection at multiple planes
          • Article
          • Peer Reviewed
          UC San Diego Previously Published Works (2019)
          Optical edge detection is a useful method for characterizing boundaries, which is also in the forefront of image processing for object detection. As the field of metamaterials and metasurface is growing fast in an effort to miniaturize optical devices at unprecedented scales, experimental realization of optical edge detection with metamaterials remains a challenge and lags behind theoretical proposals. Here, we propose a mechanism of edge detection based on a Pancharatnam-Berry-phase metasurface. We experimentally demonstrated broadband edge detection using designed dielectric metasurfaces with high optical efficiency. The metasurfaces were fabricated by scanning a focused laser beam inside glass substrate and can be easily integrated with traditional optical components. The proposed edge-detection mechanism may find important applications in image processing, high-contrast microscopy, and real-time object detection on compact optical platforms such as mobile phones and smart cameras.
            Cover page: Optical edge detection based on high-efficiency dielectric metasurface
            • Article
            • Peer Reviewed
            UC San Diego Previously Published Works (2021)
            On-chip plasmonic circuitry offers a promising route to meet the ever-increasing requirement for device density and data bandwidth in information processing. As the key building block, electrically-driven nanoscale plasmonic sources such as nanoLEDs, nanolasers, and nanojunctions have attracted intense interest in recent years. Among them, surface plasmon (SP) sources based on inelastic electron tunneling (IET) have been demonstrated as an appealing candidate owing to the ultrafast quantum-mechanical tunneling response and great tunability. However, the major barrier to the demonstrated IET-based SP sources is their low SP excitation efficiency due to the fact that elastic tunneling of electrons is much more efficient than inelastic tunneling. Here, we remove this barrier by introducing resonant inelastic electron tunneling (RIET)-follow a recent theoretical proposal-at the visible/near-infrared (NIR) frequencies and demonstrate highly-efficient electrically-driven SP sources. In our system, RIET is supported by a TiN/Al2O3 metallic quantum well (MQW) heterostructure, while monocrystalline silver nanorods (AgNRs) were used for the SP generation (localized surface plasmons (LSPs)). In principle, this RIET approach can push the external quantum efficiency (EQE) close to unity, opening up a new era of SP sources for not only high-performance plasmonic circuitry, but also advanced optical sensing applications.
              Cover page: Highly-efficient electrically-driven localized surface plasmon source enabled by resonant inelastic electron tunneling
              • Article
              • Peer Reviewed
              UC San Diego Previously Published Works (2018)
                Cover page: Efficient light generation from enhanced inelastic electron tunnelling
                • Article
                • Peer Reviewed
                UC San Diego Previously Published Works (2020)
                Metasurfaces consisting of engineered dielectric or metallic structures provide unique solutions to realize exotic phenomena including negative refraction, achromatic focusing, electromagnetic cloaking, and so on. The intersection of metasurface and quantum optics may lead to new opportunities but is much less explored. Here, we propose and experimentally demonstrate that a polarization-entangled photon source can be used to switch ON or OFF the optical edge detection mode in an imaging system based on a high-efficiency dielectric metasurface. This experiment enriches both fields of metasurface and quantum optics, representing a promising direction toward quantum edge detection and image processing with remarkable signal-to-noise ratio.
                  Cover page: Metasurface enabled quantum edge detection
                  • Article
                  • Peer Reviewed
                  UC San Diego Previously Published Works (2018)
                  Semiconductor quantum well (QW) light-emitting diodes (LEDs) have limited temporal modulation bandwidth of a few hundred MHz due to the long carrier recombination lifetime. Material doping and structure engineering typically leads to incremental change in the carrier recombination rate, whereas the plasmonic-based Purcell effect enables dramatic improvement for modulation frequency beyond the GHz limit. By stacking Ag-Si multilayers, the resulting hyperbolic metamaterials (HMMs) have shown tunability in the plasmonic density of states for enhancing light emission at various wavelengths. Here, nanopatterned Ag-Si multilayer HMMs are utilized for enhancing spontaneous carrier recombination rates in InGaN/GaN QWs. An enhancement of close to 160-fold is achieved in the spontaneous recombination rate across a broadband of working wavelengths accompanied by over tenfold enhancement in the QW peak emission intensity, thanks to the outcoupling of dominating HMM modes. The integration of nanopatterned HMMs with InGaN QWs will lead to ultrafast and bright QW LEDs with a 3 dB modulation bandwidth beyond 100 GHz for applications in high-speed optoelectronic devices, optical wireless communications, and light-fidelity networks.
                    Cover page: Nanostructuring Multilayer Hyperbolic Metamaterials for Ultrafast and Bright Green InGaN Quantum Wells
                    • Article
                    • Peer Reviewed
                    UC San Diego Previously Published Works (2021)
                    Optical analog signal processing technology has been widely studied and applied in a variety of science and engineering fields, with the advantages of overcoming the low-speed and high-power consumption associated with its digital counterparts. Much attention has been given to emerging metasurface technology in the field of optical imaging and processing systems. Here, we demonstrate, for the first time, broadband two-dimensional spatial differentiation and high-contrast edge imaging based on a dielectric metasurface across the whole visible spectrum. This edge detection method works for both intensity and phase objects simply by inserting the metasurface into a commercial optical microscope. This highly efficient metasurface performing a basic optical differentiation operation opens up new opportunities in applications of fast, compactible and power-efficient ultrathin devices for data processing and biological imaging.
                      Cover page: Two-dimensional optical spatial differentiation and high-contrast imaging
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