Towards Faster Data Transfer by Spoof Plasmonics

With the emergence of complex architectures in modern electronics such as multi-chip modules, the increasing electromagnetic cross-talk in the circuitry causes a serious issue for high-speed, reliable data transfer among the chips. This thesis aims at developing a cross-talk resilient communication technology by utilizing a special form of electromagnetic mode, called spoof surface plasmon polariton for information transfer. The technique is based on the fact that a metal wire with periodic sub-wavelength patterns can support the propagation of confined electromagnetic mode, which can suppress cross-talk noise among the adjacent channels; and thus outperform conventional electrical interconnects in a parallel, high channel density data-bus. My developed model shows that, with 1 THz carrier frequency, the optimal design of cross-talk resilient spoof plasmon data-bus would allow each channel to support as high as 300 Gbps data, the bandwidth density can reach 1 Tbps per millimeter width of data-bus, and the digital pulse modulated carrier can travel more than 5 mm distance on the substrate. I have demonstrated that spoof plasmonic interconnects, comprised of patterned metallic conductors, can simultaneously accommodate electronic TEM mode, which is superior in cross-talk suppression at low-frequencies; and spoof plasmon mode, which is superior at high-frequencies. The research work is divided into two complementary parts: developing a theory for electromagnetic property analysis of spoof plasmon waveguide, and manipulating these properties for high-speed data transfer. Based on the theory developed, I investigated the complex interplay among various figure-of-merits of data transfer in spoof plasmonics, such as bandwidth density, propagation loss, thermal noise, speed of modulation, etc. My developed model predicts that with the availability of 1 THz carrier, the bit-error-rate of spoof plasmon data bus, subject to thermal noise would be $sim10^{-8}$ while the Shannon information capacity of the bus would be $10$ Tbps/mm. The model also predicts that, by proper designing of the modulator, it can be possible to alter the transmission property of the waveguide over one-fifth ($1/5$) of the spoof plasmon band which spans from DC frequency to the frequency of spoof plasmon resonance. To exemplify, if the spoof plasmon resonance is set at $1$ THz, then we can achieve more than $200$ Gbps speed of modulation with a very high extinction ratio, assuming the switching latency of the transistors at our disposal is negligible to the time-resolution of interest. We envision spoof plasmonic interconnects to constitute the next generation communication technology that will be transferring data at hundreds of Gigabit per second (Gbps) speed among different chips on a multi-chip module (MCM) carrier or system-on-chip (SoC) packaging.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/163041/1/srjoy_1.pd

Active and Passive Plasmonic Devices for Optical Communications

A short introduction to the theory of surface plasmon polaritons (SPPs) is given. The application of the SPPs in on-chip signal processing is discussed. In particular, two concepts of plasmonic modulators are reported, wherein the SPPs are modulated by 40 Gbit/s electrical signals. Phase and Mach-Zehnder modulators employing the Pockels effect in electro-optic organic materials are discussed. A few micro-meter long SPP absorption modulator based on a thin layer of indium-tin-oxide is reported

Optomechanical Devices and Sensors Based on Plasmonic Metamaterial Absorbers

Surface plasmon resonance is the resonant oscillations of the free electrons at the interface between two media with different signs in real permittivities, e.g. a metal and a dielectric, stimulated by light. Plasmonics is a promising field of study, because electron oscillations inside a subwavelength space at optical frequencies simultaneously overcome the limit of diffraction in conventional photonics and carrier mobilities in semiconductor electronics. Due to the subwavelength confinement, plasmonic resonances can strongly enhance local fields and, hence, magnify light-matter interactions. Optical absorbers based on plasmonic metamaterials can absorb light resonantly at the operating wavelengths with up to 100% efficiency. We have explored plasmonic absorbers at infrared wavelengths for thermal detectors, e.g. a gold nanostrip antenna absorber that can absorb 10-times light using only 2% of material consumption comparing to a uniform gold film. In an optomechanical device, the optical mode and mechanical mode are mutually influenced, through the optical forces exerted on the mechanical oscillator and the detuning of optical resonance by the mechanical oscillator, so that the mechanical oscillations are either amplified or suppressed by light. We designed an optomechanical device integrated with plasmonic metamaterial absorber on a membrane mechanical oscillator, wherein a tunable Fano-resonant absorption in the absorber arises from the coupling between the plasmonic and Fabry-Perot reonsances. The absorber traps the incident light and heat up the membrane, causing an increase in thermal stress and a normal plasmomechanical force on it. This is a light-absorption-dependent elastic force arising from the opto-thermo-mechanical interactions. Due to the finite thermal response time in the membrane, the elastic plasmomechanical force is delayed and, consequently, generates a viscous component modifying the damping rate of the mechanical oscillator. We have observed optomechanical amplification and cooling in the device at designed detuning conditions. In particular, on the condition that the optomechanical gain beats the intrinsic mechanical damping, the oscillation becomes coherent, i.e. phonon lasing. We successfully demonstrated phonon lasing with a threshold power of 19 μW. This device is promising as an integration-ready coherent phonon source and may set the stage for applications in fundamental studies and ultrasonic imaging modalities

Wireless Terahertz Communications: Optoelectronic Devices and Signal Processing

Novel THz device concepts and signal processing schemes are introduced and experimentally confirmed. Record-high data rates are achieved with a simple envelope detector at the receiver. Moreover, a THz communication system using an optoelectronic receiver and a photonic local oscillator is shown for the first time, and a new class of devices for THz transmitters and receivers is investigated which enables a monolithic co-integration of THz components with advanced silicon photonic circuits

Silicon - polymer hybrid integrated microwave photonic devices for optical interconnects and electromagnetic wave detection

textThe accelerating increase in information traffic demands the expansion of optical access network systems that require high-performance optical and photonic components. In short-range communication links, optical interconnects have been widely accepted as a viable approach to solve the problems that copper based electrical interconnects have encountered in keeping up with the surge in the data rate demand over the last decades. Low cost, ease of fabrication, and integration capabilities of low optical-loss polymers make them attractive for integrated photonic applications to support futuristic data communication networks. In addition to passive wave-guiding components, electro-optic (EO) polymers consisting of a polymeric matrix doped with organic nonlinear chromophores have enabled wide-RF-bandwidth and low-power active photonic devices. Beside board level passive and active optical components, on-chip micro- or nano-photonic devices have been made possible by the hybrid integration of EO polymers onto the silicon platform. In recent years, silicon photonics have attracted a significant amount of attentions, because it offers compact device size and the potential of complementary metal–oxide–semiconductor (CMOS) compatible photonic integrated circuits. The combination of silicon photonics and EO polymers can enable miniaturized and high-performance hybrid integrated photonic devices, such as electro-optic modulators, optical interconnects, and microwave photonic sensors. Silicon photonic crystal waveguides (PCWs) exhibit slow-light effects which are beneficial for device miniaturization. Especially, EO polymer filled silicon slotted PCWs further reduce the device size and enhance the device performance by combining the best of these two systems. The potential applications of these silicon-polymer hybrid integrated devices include not only optical interconnects, but also optical sensing and microwave photonics. In this dissertation, the design, fabrication, and characterization of several types of silicon-polymer hybrid photonic devices will be presented, including EO polymer filled silicon PCW modulators for on-chip optical interconnects, antenna-coupled optical modulators for electromagnetic wave detections, and low-loss strip-to-slot PCW mode converters. In addition, some polymer-based devices and silicon-based photonic devices will also be presented, such as traveling wave electro-optic polymer modulators based on domain-inversion directional couplers, and silicon thermo-optic switches based on coupled photonic crystal microcavities. Furthermore, some microwave (or RF) components such as integrated broadband bowtie antennas for microwave photonic applications will be covered. Some on-going work or suggested future work will also be introduced, including in-device pyroelectric poling for EO polymer filled silicon slot PCWs, millimeter- or Terahertz-wave sensors based on EO polymer filled plasmonic slot waveguide, low-loss silicon-polymer hybrid slot photonic crystal waveguides fabricated by CMOS foundry, logic devices based on EO polymer microring resonators, and so on.Electrical and Computer Engineerin

A review of gallium nitride LEDs for multi-gigabit-per-second visible light data communications

The field of visible light communications (VLC) has gained significant interest over the last decade, in both fibre and free-space embodiments. In fibre systems, the availability of low cost plastic optical fibre (POF) that is compatible with visible data communications has been a key enabler. In free-space applications, the availability of hundreds of THz of the unregulated spectrum makes VLC attractive for wireless communications. This paper provides an overview of the recent developments in VLC systems based on gallium nitride (GaN) light-emitting diodes (LEDs), covering aspects from sources to systems. The state-of-the-art technology enabling bandwidth of GaN LEDs in the range of >400 MHz is explored. Furthermore, advances in key technologies, including advanced modulation, equalisation, and multiplexing that have enabled free-space VLC data rates beyond 10 Gb/s are also outlined

Ultra-broadband surface-normal coherent optical receiver with nanometallic polarizers

A coherent receiver that can demodulate high-speed in-phase and quadrature signals of light is an essential component for optical communication, interconnects, imaging, and computing. Conventional waveguide-based coherent receivers, however, exhibit large footprints, difficulty in coupling a large number of spatial channels efficiently, and limited operating bandwidth imposed by the waveguide-based optical hybrid. Here, we present a surface-normal coherent receiver with nanometallic-grating-based polarizers integrated directly on top of photodetectors without the need for an optical hybrid circuit. Using a fabricated device with the active section occupying a 70-{\mu}m-square footprint, we demonstrate demodulation of high-speed (up to 64 Gbaud) coherent signals in various formats. Moreover, ultra-broadband operation from 1260 nm to 1630 nm is demonstrated, thanks to the wavelength-insensitive nanometallic polarizers. To our knowledge, this is the first demonstration of a surface-normal homodyne optical receiver, which can easily be scaled to a compact two-dimensional arrayed device to receive highly parallelized coherent signals.Comment: 23 pages, 4 figures (main manuscript) + 4 pages, 2 figures (supporting info

Active and Passive Plasmonic Devices for Optical Communications

In this book, novel plasmonic devices are designed and demonstrated. In particular, an ultra-compact phase modulator is reported by exploiting plasmonics and Pockels effect in electro-optic organic materials. An absorption modulator with a length of few micrometers is designed and demonstrated. To efficiently interface plasmonics with low loss silicon photonics, novel photonic-to-plasmonic mode converters were developed. Finally, a new ultra-compact polarization beam splitter (PBS) is presented

Polymer-based integrated photonic devices for interconnects

Integrated photonic devices based on optical waveguides have been extensively studied for various applications, especially the high-speed intra- and inter-chip interconnects. Usually, a waveguide contains a core with high refractive index and cladding with lower refractive index. Among various waveguides, silicon, polymer, and silicon-polymer hybrid devices are the most promising candidates for low cost, small size, light weight, and low power consumption (CSWaP) optical interconnect. Firstly, silicon-based optical devices can be fabricated using CMOS compatible nanofabrication technology, which is already widely used to manufacture integrated circuits. Silicon photonic devices can have very small footprint and enable high density photonic circuits, due to high refractive index contrast. However, one of the intrinsic obstacles is the absence of χ⁽²⁾-nonlinearity in unstrained silicon due to its centrosymmetric crystal structure, making modulating photons on silicon platform a great challenge. Secondly, polymer-based devices have been found very attractive, owing to the advantages of high thermo-optic (TO) or electro-optic (EO) coefficient, high transparency in the telecommunication wavelength windows, and fabrication feasibility over large areas on printed circuit board (PCB) or other kinds of substrates. The roll-to-roll (R2R) compatible imprinting and ink-jet printing for developing polymer-based devices on flexible or rigid substrates enable large-area, light-weight, low-cost optical interconnects. However, due to the low refractive index contrast, the polymer photonic devices always require large footprint. Finally, the silicon-organic hybrid (SOH) platform enables the marriage of the best of these two materials and thus has been receiving substantial attention. In this dissertation, integrated photonic devices based on silicon, polymer, or hybrid platform will be presented. First, high-efficiency quasi-vertical tapers for polymer waveguide based inter-board optical interconnects will be demonstrated. A triangular-shape tapered structure is adopted above the waveguide core to transform a fiber mode into a single mode polymer rib waveguide mode as an optical mode transformer. A coupling loss of 1.79±0.30 dB and 2.23±0.31 dB per coupler for the quasi-TM and quasi-TE mode respectively have been experimentally demonstrated, across the C and L bands (1535 nm – 1610 nm). Then, a reconfigurable thermo-optic polymer switch based true-time-delay network will be analyzed and demonstrated. Thirdly, I will show a novel subwavelength-grating waveguide ring resonator based high-speed modulators, which is the largest bandwidth and the most compact footprint that has been demonstrated for the ring resonators on the silicon-organic hybrid (SOH) platform. Finally, the on-chip time-division multiplexing and de-multiplexing system will be designed and analyzed.Electrical and Computer Engineerin

Next Generation Silicon Photonic Transceiver: From Device Innovation to System Analysis

Silicon photonics is recognized as a disruptive technology that has the potential to reshape many application areas, for example, data center communication, telecommunications, high-performance computing, and sensing. The key capability that silicon photonics offers is to leverage CMOS-style design, fabrication, and test infrastructure to build compact, energy-efficient, and high-performance integrated photonic systems-on- chip at low cost. As the need to squeeze more data into a given bandwidth and a given footprint increases, silicon photonics becomes more and more promising. This work develops and demonstrates novel devices, methodologies, and architectures to resolve the challenges facing the next-generation silicon photonic transceivers. The first part of this thesis focuses on the topology optimization of passive silicon photonic devices. Specifically, a novel device optimization methodology - particle swarm optimization in conjunction with 3D finite-difference time-domain (FDTD), has been proposed and proven to be an effective way to design a wide range of passive silicon photonic devices. We demonstrate a polarization rotator and a 90◦ optical hybrid for polarization-diversity and phase-diversity communications - two important schemes to increase the communication capacity by increasing the spectral efficiency. The second part of this thesis focuses on the design and characterization of the next- generation silicon photonic transceivers. We demonstrate a polarization-insensitive WDM receiver with an aggregate data rate of 160 Gb/s. This receiver adopts a novel architecture which effectively reduces the polarization-dependent loss. In addition, we demonstrate a III-V/silicon hybrid external cavity laser with a tuning range larger than 60 nm in the C-band on a silicon-on-insulator platform. A III-V semiconductor gain chip is hybridized into the silicon chip by edge-coupling to the silicon chip. The demonstrated packaging method requires only passive alignment and is thus suitable for high-volume production. We also demonstrate all silicon-photonics-based transmission of 34 Gbaud (272 Gb/s) dual-polarization 16-QAM using our integrated laser and silicon photonic coherent transceiver. The results show no additional penalty compared to commercially available narrow linewidth tunable lasers. The last part of this thesis focuses on the chip-scale optical interconnect and presents two different types of reconfigurable memory interconnects for multi-core many-memory computing systems. These reconfigurable interconnects can effectively alleviate the memory access issues, such as non-uniform memory access, and Network-on-Chip (NoC) hot-spots that plague the many-memory computing systems by dynamically directing the available memory bandwidth to the required memory interface