arXiv subjects

Volker J. Sorger

Publications and source records attributed to Volker J. Sorger.

85 records · Page 5Linked to original sources

arXiv2017

D3NOC: Dynamic Data-Driven Network On Chip in Photonic Electronic Hybrids

In this paper, we present a reconfigurable hybrid Photonic-Plasmonic Network-on-Chip (NoC) based on the Dynamic Data Driven Application System (DDDAS) paradigm. In DDDAS computations and measurements form a dynamic closed feedback loop in which they tune one another in response to changes in the environment. Our proposed system enables dynamic augmentation of a base electrical mesh topology with an optical express bus during the run-time. In addition, the measurement process itself adjusts to the environment. In order to achieve lower latencies, lower dynamic power, and higher throughput, we take advantage of a Configurable Hybrid Photonic Plasmonic Interconnect (CHyPPI) for our reconfigurable connections. We evaluate the performance and power of our system against kernels from NAS Parallel Benchmark (NPB) in addition to some synthetically generated traffic. In comparison to a 16x16 base electrical mesh, D3NOC shows up to 89% latency and 67% dynamic power net improvements beyond overhead-corrected performance. It should be noted that the design-space of NoC reconfiguration is vast and the goal of this study is not design-space exploration. Our goal is to show the potentials of adaptive dynamic measurements when coupled with other reconfiguration techniques in the NoC context.

cs.OH↗

arXiv2017

Dual-wavelength generation and tuning by controlling the apodized grating depth in microring resonators

Here we show a photonic design for tunable dual-wavelength generation deploying optical nonlinear mode coupling of two coupled III-V semiconductor microring resonators (MRRs) connected to a pump and drop waveguide buses. Here one of the two rings contains a grating, while the other has a planar surface. The underling mechanism for the dual wavelength generation originates from the resonance-detuning of the spectra resulting in non-linear mode mixing. Tunability of the wavelengths is achieved by altering the grating depth of the MRR and the power coupling coefficients. For the grating design of the MRR we select a trapezoidal-profiled apodized grating to gain low reflectivity at sidelobes. A time-domain travelling wave (TDTW) analysis gives a InGaAsP core refractive index of 3.3 surrounded by a grating InP cladding with n=3.2. We further confirm that the propagation of a Gaussian pulse input with 10 mW power and bandwidth of 0.76 ps is well confined within the mode propagation of the system. Taken together our results show a 2:1 fan-out of two spectrally separate signals for compact and high functional sources on chip.

physics.optics↗

arXiv2017

Channel resolution enhancement through scalability of nano/micro-scale thickness and width of SU-8 polymer based optical channels using UV lithography

This paper reports on an approach for fabrication of micro-channels with nanometer thickness achieved by optimization of UV lithography processes. Rectangular micro-channels with a staple edge are fabricated over the surface of a silicon wafer substrate in which a sub-micron layer of diluted SU-8 thin film has been coated. The optimization of the process parameters including the duration of a two-step pre- and post-baking process, UV exposure dosage, and finally chemical developing time with constant agitation produces micro-channels with high contrast edges and thickness below 100 nm is achieved. The dimensions achieved using this approach has potential applications in sub-micron optical waveguides and nanoelectromechanical (NEMS) devices.

physics.app-ph↗

arXiv2017

2D Materials in Electro-optic Modulation: energy efficiency, electrostatics, mode overlap, material transfer and integration

Here we discuss the physics of electro-optic modulators deploying 2D materials. We include a scaling laws analysis showing how energy-efficiency and speed change for three underlying cavity systems as a function of critical device length scaling. A key result is that the energy-per-bit of the modulator is proportional to the volume of the device, thus making the case for submicron-scale modulators possible deploying a plasmonic optical mode. We then show how Graphenes Pauli-blocking modulation mechanism is sensitive to the device operation temperature, whereby a reduction of the temperature enables a 10x reduction in modulator energy efficiency. Furthermore, we show how the high index tunability of Graphene is able to compensate for the small optical overlap factor of 2D-based material modulators, which is unlike classical Silicon-based dispersion devices. Lastly we demonstrate a novel method towards a 2D material printer suitable for cross-contamination free and on-demand printing. The latter paves the way to integrate 2D materials seamlessly into taped-out photonic chips.

cond-mat.mes-hall↗

arXiv2017

MorphoNoC: Exploring the Design Space of a Configurable Hybrid NoC using Nanophotonics

As diminishing feature sizes drive down the energy for computations, the power budget for on-chip communication is steadily rising. Furthermore, the increasing number of cores is placing a huge performance burden on the network-on-chip (NoC) infrastructure. While NoCs are designed as regular architectures that allow scaling to hundreds of cores, the lack of a flexible topology gives rise to higher latencies, lower throughput, and increased energy costs. In this paper, we explore MorphoNoCs - scalable, configurable, hybrid NoCs obtained by extending regular electrical networks with configurable nanophotonic links. In order to design MorphoNoCs, we first carry out a detailed study of the design space for Multi-Write Multi-Read (MWMR) nanophotonics links. After identifying optimum design points, we then discuss the router architecture for deploying them in hybrid electronic-photonic NoCs. We then study explore the design space at the network level, by varying the waveguide lengths and the number of hybrid routers. This affords us to carry out energy-latency trade-offs. For our evaluations, we adopt traces from synthetic benchmarks as well as the NAS Parallel Benchmark suite. Our results indicate that MorphoNoCs can achieve latency improvements of up to 3.0x or energy improvements of up to 1.37x over the base electronic network.

cs.OH↗

arXiv2017

HyPPI NoC: Bringing Hybrid Plasmonics to an Opto-Electronic Network-on-Chip

As we move towards an era of hundreds of cores, the research community has witnessed the emergence of opto-electronic network on-chip designs based on nanophotonics, in order to achieve higher network throughput, lower latencies, and lower dynamic power. However, traditional nanophotonics options face limitations such as large device footprints compared with electronics, higher static power due to continuous laser operation, and an upper limit on achievable data rates due to large device capacitances. Nanoplasmonics is an emerging technology that has the potential for providing transformative gains on multiple metrics due to its potential to increase the light-matter interaction. In this paper, we propose and analyze a hybrid opto-electric NoC that incorporates Hybrid Plasmonics Photonics Interconnect (HyPPI), an optical interconnect that combines photonics with plasmonics. We explore various opto-electronic network hybridization options by augmenting a mesh network with HyPPI links, and compare them with the equivalent options afforded by conventional nanophotonics as well as pure electronics. Our design space exploration indicates that augmenting an electronic NoC with HyPPI gives a performance to cost ratio improvement of up to 1.8x. To further validate our estimates, we conduct trace based simulations using the NAS Parallel Benchmark suite. These benchmarks show latency improvements up to 1.64x, with negligible energy increase. We then further carry out performance and cost projections for fully optical NoCs, using HyPPI as well as conventional nanophotonics. These futuristic projections indicate that all-HyPPI NoCs would be two orders more energy efficient than electronics, and two orders more area efficient than all-photonic NoCs.

cs.ET↗

arXiv2017

Testbeds for Transition Metal Dichalcogenide Photonics: Efficacy of Light Emission Enhancement in Monomer vs. Dimer Nanoscale Antennae

Monolayer transition metal dichalcogenides are uniquely-qualified materials for photonics because they combine well defined tunable direct band gaps and selfpassivated surfaces without dangling bonds. However, the atomic thickness of these 2D materials results in low photo absorption limiting the achievable photo luminescence intensity. Such emission can, in principle, be enhanced via nanoscale antennae resulting in; a. an increased absorption cross-section enhancing pump efficiency, b. an acceleration of the internal emission rate via the Purcell factor mainly by reducing the antennas optical mode volume beyond the diffraction limit, and c. improved impedance matching of the emitter dipole to the freespace wavelength. Plasmonic dimer antennae show orders of magnitude hot-spot field enhancements when an emitter is positioned exactly at the midgap. However, a 2D material cannot be grown, or easily transferred, to reside in mid-gap of the metallic dimer cavity. In addition, a spacer layer between the cavity and the emissive material is required to avoid non-radiative recombination channels. Using both computational and experimental methods, in this work we show that the emission enhancement from a 2D emitter- monomer antenna cavity system rivals that of dimers at much reduced lithographic effort. We rationalize this finding by showing that the emission enhancement in dimer antennae does not specifically originate from the gap of the dimer cavity, but is an average effect originating from the effective cavity crosssection taken below each optical cavity where the emitting 2D film is located. In particular, we test an array of different dimer and monomer antenna geometries and observe a representative 3x higher emission for both monomer and dimer cavities as compared to intrinsic emission of Chemical Vapor Deposition synthesized WS2 flakes.

cond-mat.mes-hall↗

arXiv2016

Moore's Law in CLEAR Light

The inability of Moore's Law and other figure-of-merits (FOMs) to accurately explain the technology development of the semiconductor industry demands a holistic merit to guide the industry. Here we introduce a FOM termed CLEAR that accurately postdicts technology developments since the 1940's until today, and predicts photonics as a logical extension to keep-up the pace of information-handling machines. We show that CLEAR (Capability-to-Latency-Energy-Amount-Resistance) is multi-hierarchical applying to the device, interconnect, and system level. Being a holistic FOM, we show that empirical trends such as Moore's Law and the Makimoto's wave are special cases of the universal CLEAR merit. Looking ahead, photonic board- and chip-level technologies are able to continue the observed doubling rate of the CLEAR value every 12 months, while electronic technologies are unable to keep pace.

cs.ET↗

arXiv2016

Active Material, Optical Mode and Cavity Impact on electro-optic Modulation Performance

In this paper, three different materials Si, ITO and graphene; and three different types of mode structures bulk, slot and hybrid; based on their electrooptical and electro absorptive aspects in performance are analyzed. The study focuses on three major characteristics of electrooptic tuning, i.e. material, modal and cavity dependency. The materials are characterized with established models and the allowed ranges for their key parameter spectra are analyzed with desired tuning in mind; categorizing into n and k dominant regions for plausible electrooptic and electro absorptive applications, respectively. A semi analytic approach, with the aid of FEM simulations for the eigenmode calculations, was used for this work. Electrooptic tuning i.e. resonance shift properties inside Fabry Perot cavities are investigated with modal and scaling concerns in mind. Tuning changes the effective complex refractive index of the mode dictated by the Kramers Kronig relations which subsequently suggest a tradeoff between the resonance shift and increasing losses. The electrical tuning properties of the different modes in the cavity are analyzed, and subsequently a figure of merit, delta-lambda/delta-alpha was chosen with respect to carrier concentration and cavity scaling to find prospective suitable regions for desired tuning effects.

cond-mat.mes-hall↗

arXiv2016

Graphene-based Solitons for Spatial Division Multiplexed Switching

Spatial division multiplexing utilizes the directionality of lights propagating k-vector to separate it into distinct spatial directions. Here we show that the anisotropy of orthogonal spatial Solitons propagating in a single Graphene monolayer results in phase-based multiplexing. We use the self- confinement properties of spatial Solitons to increase the usable density of states (DOS) of this switching-system. Furthermore, we show that crossing two orthogonal Solitons exhibit a low (0.035 dB) mutual disturbance from another enabling independent k-vector switching. The efficient utilization of the DOS and multiplexing in real-space enables data processing parallelism with applications in optical networking and computing.

cond-mat.mes-hall↗

arXiv2016

A Universal Multi-Hierarchy Figure-of-Merit for On-Chip Computing and Communications

Continuing demands for increased compute efficiency and communication bandwidth have led to the development of novel interconnect technologies with the potential to outperform conventional electrical interconnects. With a plurality of interconnect technologies to include electronics, photonics, plasmonics, and hybrids thereof, the simple approach of counting on-chip devices to capture performance is insufficient. While some efforts have been made to capture the performance evolution more accurately, they eventually deviate from the observed development pace. Thus, a holistic figure of merit (FOM) is needed to adequately compare these recent technology paradigms. Here we introduce the Capability-to-Latency-Energy-Amount-Resistance (CLEAR) FOM derived from device and link performance criteria of both active optoelectronic devices and passive components alike. As such CLEAR incorporates communication delay, energy efficiency, on-chip scaling and economic cost. We show that CLEAR accurately describes compute development including most recent machines. Since this FOM is derived bottom-up, we demonstrate remarkable adaptability to applications ranging from device-level to network and system-level. Applying CLEAR to benchmark device, link, and network performance against fundamental physical compute and communication limits shows that photonics is competitive even for fractions of the die-size, thus making a case for on-chip optical interconnects.

cs.ET↗

arXiv2016

Scattering and Absorption Control in Biocompatible Fibers towards Equalized Photobiomodulation

Transparent tissue scaffolds enable illumination of growing tissue to accelerate cell proliferation and improve other cell functions through photobiomodulation. The biphasic dose response of cells exposed to photobiomodulating light dictates that the illumination to be evenly distributed across the scaffold such that the cells are neither under nor over exposed to light. However, equalized illumination has not been sufficiently addressed. Here we analyze and experimentally demonstrate spatially equalizing illumination by three methods, namely, engineered surface scattering, reflection by a gold mirror, and traveling-waves in a ring mesh. Our results show that nearly equalized illumination is achievable by controlling the light scattering-to-loss ratio. This demonstration opens opportunities for dose-optimized photobiomodulation in tissue regeneration.

physics.bio-ph↗

arXiv2015

A compact plasmonic MOS-based 2x2 electro-optic switch

We report on a three-waveguide electro-optic switch for compact photonic integrated circuits and data routing applications. The device features a plasmonic metal-oxide-semiconductor (MOS) mode for enhanced light-matter-interactions. The switching mechanism originates from a capacitor-like design where the refractive index of the active medium, Indium-Tin-Oxide, is altered via shifting the plasma frequency due to carrier accumulation inside the waveguide-based MOS structure. This light manipulation mechanism controls the transmission direction of transverse magnetic polarized light into either a CROSS or BAR waveguide port. The extinction ratio of 18 dB (7) dB for the CROSS (BAR) state, respectively, is achieved via a gating voltage bias. The ultrafast broadband fJ/bit device allows for seamless integration with Siliconon- Insulator platforms to for low-cost manufacturing.

physics.optics↗