Since the first report of the extraordinary optical transmission (EOT) phenomenon through periodic subwavelength hole arrays milled in optically-thick metal film, plasmonics have generated ...considerable interest because they enable new fundamental science and application technologies. Central to this phenomenon is the role of surface plasmon polaritons (SPPs), which are essentially electromagnetic waves trapped at the interface between a metal and a dielectric medium through their interactions with free electrons at the metal surface. The resonant interaction between the incident light and surface charge oscillations enables the concentration and manipulation of light at deep subwavelength scales, opening up exciting application opportunities ranging from subwavelength optics and optoelectronics to bio/chemical sensing. Furthermore, additional phenomena arise as the thickness of metal film decreases to be comparable to its skin depth (optically-thin), and the single-interface SPPs on the top and bottom metal surfaces combine to form two coupled SPPs, the long-range and short-range SPPs. Until now, much less work has focused on the study of surface plasmon resonances (SPRs) in ultrathin nanostructured metals. This dissertation seeks to elucidate underlying physical mechanisms of SPRs in ultrathin nanostructured metals and tailor them for practical applications. Inspired by state-of-the-art advances on plasmonics in optically-thick nanostructured metals, one- (1D) and two-dimensional (2D) ultrathin plasmonic nanostructures are exploited for particular applications in three essential areas: photovoltaics, color filters and biosensors, achieving superior performances compared with their optically-thick counterparts. More specifically, this thesis is focused on systematic investigations on: (1) plasmonic transparent electrodes for organic photovoltaics and polarization-insensitive optical absorption enhancement in the active layer; (2) plasmonic subtractive color filters with record-high transmission efficiency and other unique properties; (3) rapid and highly-sensitive plasmonic bio-sensors employing ultrathin nanogratings. The successful development of these new plasmonic platforms have far-reaching impact on green energy technologies, next-generation displays and imagers, and label-free bio-sensing for point-of-care diagnostics.
Metamaterials/metasurfaces have enabled unprecedented manipulation of electromagnetic waves. Here we present a new design of metasurface structure functioning as antireflection coatings. The ...structure consists of a subwavelength metallic mesh capped with a thin dielectric layer on top of a substrate. By tailoring the geometric parameters of the metallic mesh and the refractive index and thickness of the capping dielectric film, reflection from the substrate can be completely eliminated at a specific frequency. Compared to traditional methods such as coatings with single- or multi-layer dielectric films, the metasurface antireflection coatings are much thinner and the requirement of index matching is largely lifted. Here, this approach is particularly suitable for antireflection coatings in the technically challenging terahertz frequency range and is also applicable in other frequency regimes.
A super-resolution imaging method for the deep sub-wavelength structure has been proposed, which is achieved by controlling the propagating direction of the evanescent components of the incident ...field through a one-dimensional metamaterial structure (ODMS) with an anisotropic dielectric permittivity. We provide the mechanism of this kind of super-resolution imaging method in detail and discuss some factors influencing image quality. A two-dimensional finite element method (FEM) has been used to verify the imaging mechanism. Furthermore, the same sub-diffraction limited image could be obtained at different incident wavelengths at the far side of the imaging structure with different working distances.
We investigate the optical absorption enhancement in molecular OPVs, in which an ultrathin Ag nanogrid is employed as a transparent electrode. A very high total photon absorptivity of 0.49 is ...predicted for such OPV architecture.
We report a novel plasmonic interferomer for intensity-based sensing with high FOMs* exceeding 140. This is achieved by means of destructive SPP-light interference, which provides near-perfect light ...cancellation for sensitive low-background detection.
Broadband light absorption enhancement is numerically investigated for double plasmonic structures in thin-film organic photovoltaics. Due to the combined excitation of different Surface Plasmon ...modes, the absorption enhancement of about 67% is obtained.
Practical quantum networks will require quantum nodes consisting of many memory qubits. This in turn will increase the complexity of the photonic circuits needed to control each qubit and will ...require strategies to multiplex memories and overcome the inhomogeneous distribution of their transition frequencies. Integrated photonics operating at visible to near-infrared (VNIR) wavelength range, compatible with the transition frequencies of leading quantum memory systems, can provide solutions to these needs. In this work, we realize a VNIR thin-film lithium niobate (TFLN) integrated photonics platform with the key components to meet these requirements. These include low-loss couplers (\(<\) 1 dB/facet), switches (\(>\) 20 dB extinction), and high-bandwidth electro-optic modulators (\(>\) 50 GHz). With these devices we demonstrate high-efficiency and CW-compatible frequency shifting (\(>\) 50 \(\%\) efficiency at 15 GHz), as well as simultaneous laser amplitude and frequency control through a nested modulator structure. Finally, we highlight an architecture for multiplexing quantum memories using the demonstrated TFLN components, and outline how this platform can enable a 2-order of magnitude improvement in entanglement rates over single memory nodes. Our results demonstrate that TFLN can meet the necessary performance and scalability benchmarks to enable large-scale quantum nodes.
Robust, low-loss photonic packaging of on-chip nanophotonic circuits is a key enabling technology for the deployment of integrated photonics in a variety of classical and quantum technologies ...including optical communications and quantum communications, sensing, and transduction. To date, no process has been established that enables permanent, broadband, and cryogenically-compatible coupling with sub-dB losses from optical fibers to nanophotonic circuits. Here we report a technique for reproducibly generating a permanently packaged interface between a tapered optical fiber and nanophotonic devices with a record-low coupling loss < 1 dB per facet at near-infrared wavelengths (~730 nm) that remains stable from 300 K to 30 mK. We further demonstrate the compatibility of this technique with etched lithium niobate on insulator waveguides. The technique lifts performance limitations imposed by scattering as light transfers between photonic devices and optical fibers, paving the way for scalable integration of photonic technologies at both room and cryogenic temperatures.
Co-packaged optics require novel packaging concepts for high fiber counts and low-cost assembly. We design and fabricate a glass waveguide substrate with MPO interfaces that yield an average ...connector loss of 0.5 dB. Simulations are performed to assess the required spring force for physical contact.
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