The Experts below are selected from a list of 603 Experts worldwide ranked by ideXlab platform

Oskar Painter - One of the best experts on this subject based on the ideXlab platform.

  • design of a quasi 2d photonic crystal optomechanical cavity with tunable large x 2 coupling
    Optics Express, 2016
    Co-Authors: Mahmoud Kalaee, T K Paraiso, Hannes Pfeifer, Oskar Painter
    Abstract:

    We present the optical and mechanical design of a mechanically compliant quasi-two-dimensional photonic crystal cavity formed from thin-film silicon in which a pair of linear nanoscale slots are used to create two coupled high-Q optical resonances. The optical cavity supermodes, whose frequencies are designed to lie in the 1500 nm wavelength band, are shown to interact strongly with mechanical resonances of the structure whose frequencies range from a few MHz to a few GHz. Depending upon the symmetry of the mechanical modes and the symmetry of the slot sizes, we show that the optomechanical coupling between the optical supermodes can be either linear or quadratic in the mechanical displacement amplitude. Tuning of the nanoscale slot size is also shown to adjust the magnitude and sign of the cavity supermode splitting 2J, enabling near-resonant motional scattering between the two optical supermodes and greatly enhancing the x^2-coupling strength. Specifically, for the fundamental flexural mode of the central nanobeam of the structure at 10 MHz the per-phonon linear cross-mode coupling rate is calculated to be be g+−/2π=1MHz, corresponding to a per-phonon x^2-coupling rate of g′/2π=1kHz for a mode splitting 2J/2π = 1 GHz which is greater than the radiation-limited supermode linewidths.

  • position squared coupling in a tunable photonic crystal optomechanical cavity
    Physical Review X, 2015
    Co-Authors: T K Paraiso, Mahmoud Kalaee, L Y Zang, Hannes Pfeifer, Florian Marquardt, Oskar Painter
    Abstract:

    We present the design, fabrication, and characterization of a planar silicon photonic crystal cavity in which large position-squared optomechanical coupling is realized. The device consists of a double-slotted photonic crystal structure in which motion of a central beam mode couples to two high-Q optical modes localized around each slot. Electrostatic tuning of the structure is used to controllably hybridize the optical modes into supermodes that couple in a quadratic fashion to the motion of the beam. From independent measurements of the anticrossing of the optical modes and of the dynamic optical spring effect, a position-squared vacuum coupling rate as large as g'/2π=245  Hz is inferred between the optical supermodes and the fundamental in-plane mechanical resonance of the structure at ω_m/2π=8.7  MHz, which in displacement units corresponds to a coupling coefficient of g'/2π=1  THz/nm 2. For larger supermode splittings, selective excitation of the individual optical supermodes is used to demonstrate optical trapping of the mechanical resonator with measured g'/2π=46  Hz.

T K Paraiso - One of the best experts on this subject based on the ideXlab platform.

  • design of a quasi 2d photonic crystal optomechanical cavity with tunable large x 2 coupling
    Optics Express, 2016
    Co-Authors: Mahmoud Kalaee, T K Paraiso, Hannes Pfeifer, Oskar Painter
    Abstract:

    We present the optical and mechanical design of a mechanically compliant quasi-two-dimensional photonic crystal cavity formed from thin-film silicon in which a pair of linear nanoscale slots are used to create two coupled high-Q optical resonances. The optical cavity supermodes, whose frequencies are designed to lie in the 1500 nm wavelength band, are shown to interact strongly with mechanical resonances of the structure whose frequencies range from a few MHz to a few GHz. Depending upon the symmetry of the mechanical modes and the symmetry of the slot sizes, we show that the optomechanical coupling between the optical supermodes can be either linear or quadratic in the mechanical displacement amplitude. Tuning of the nanoscale slot size is also shown to adjust the magnitude and sign of the cavity supermode splitting 2J, enabling near-resonant motional scattering between the two optical supermodes and greatly enhancing the x^2-coupling strength. Specifically, for the fundamental flexural mode of the central nanobeam of the structure at 10 MHz the per-phonon linear cross-mode coupling rate is calculated to be be g+−/2π=1MHz, corresponding to a per-phonon x^2-coupling rate of g′/2π=1kHz for a mode splitting 2J/2π = 1 GHz which is greater than the radiation-limited supermode linewidths.

  • position squared coupling in a tunable photonic crystal optomechanical cavity
    Physical Review X, 2015
    Co-Authors: T K Paraiso, Mahmoud Kalaee, L Y Zang, Hannes Pfeifer, Florian Marquardt, Oskar Painter
    Abstract:

    We present the design, fabrication, and characterization of a planar silicon photonic crystal cavity in which large position-squared optomechanical coupling is realized. The device consists of a double-slotted photonic crystal structure in which motion of a central beam mode couples to two high-Q optical modes localized around each slot. Electrostatic tuning of the structure is used to controllably hybridize the optical modes into supermodes that couple in a quadratic fashion to the motion of the beam. From independent measurements of the anticrossing of the optical modes and of the dynamic optical spring effect, a position-squared vacuum coupling rate as large as g'/2π=245  Hz is inferred between the optical supermodes and the fundamental in-plane mechanical resonance of the structure at ω_m/2π=8.7  MHz, which in displacement units corresponds to a coupling coefficient of g'/2π=1  THz/nm 2. For larger supermode splittings, selective excitation of the individual optical supermodes is used to demonstrate optical trapping of the mechanical resonator with measured g'/2π=46  Hz.

Adnan Yazici - One of the best experts on this subject based on the ideXlab platform.

  • an adaptive energy aware and distributed fault tolerant topology control algorithm for heterogeneous wireless sensor networks
    Ad Hoc Networks, 2016
    Co-Authors: Fatih Deniz, Hakki Bagci, Ibrahim Korpeoglu, Adnan Yazici
    Abstract:

    This paper introduces an adaptive, energy-aware and distributed fault-tolerant topology-control algorithm, namely the Adaptive Disjoint Path Vector (ADPV) algorithm, for heterogeneous wireless sensor networks. In this heterogeneous model, we have resource-rich Supernodes as well as ordinary sensor nodes that are supposed to be connected to the Supernodes. Unlike the static alternative Disjoint Path Vector (DPV) algorithm, the focus of ADPV is to secure supernode connectivity in the presence of node failures, and ADPV achieves this goal by dynamically adjusting the sensor nodes' transmission powers. The ADPV algorithm involves two phases: a single initialization phase, which occurs at the beginning, and restoration phases, which are invoked each time the network's supernode connectivity is broken. Restoration phases utilize alternative routes that are computed at the initialization phase by the help of a novel optimization based on the well-known set-packing problem. Through extensive simulations, we demonstrate that ADPV is superior in preserving supernode connectivity. In particular, ADPV achieves this goal up to a failure of 95% of the sensor nodes; while the performance of DPV is limited to 5%. In turn, by our adaptive algorithm, we obtain a two-fold increase in supernode-connected lifetimes compared to DPV algorithm.

  • a distributed fault tolerant topology control algorithm for heterogeneous wireless sensor networks
    IEEE Transactions on Parallel and Distributed Systems, 2015
    Co-Authors: Hakki Bagci, Ibrahim Korpeoglu, Adnan Yazici
    Abstract:

    This paper introduces a distributed fault-tolerant topology control algorithm, called the Disjoint Path Vector (DPV), for heterogeneous wireless sensor networks composed of a large number of sensor nodes with limited energy and computing capability and several Supernodes with unlimited energy resources. The DPV algorithm addresses the $k$ -degree Anycast Topology Control problem where the main objective is to assign each sensor’s transmission range such that each has at least $k$ -vertex-disjoint paths to Supernodes and the total power consumption is minimum. The resulting topologies are tolerant to $k-1$ node failures in the worst case. We prove the correctness of our approach by showing that topologies generated by DPV are guaranteed to satisfy $k$ -vertex supernode connectivity. Our simulations show that the DPV algorithm achieves up to 4-fold reduction in total transmission power required in the network and 2-fold reduction in maximum transmission power required in a node compared to existing solutions.

Shuhui Yang - One of the best experts on this subject based on the ideXlab platform.

  • algorithms for fault tolerant topology in heterogeneous wireless sensor networks
    IEEE Transactions on Parallel and Distributed Systems, 2008
    Co-Authors: Mihaela Cardei, Shuhui Yang
    Abstract:

    This paper addresses fault-tolerant topology control in a heterogeneous wireless sensor network consisting of several resource-rich Supernodes, used for data relaying, and a large number of energy-constrained wireless sensor nodes. We introduce the k-degree anycast topology control (fc-ATC) problem, with the objective of selecting each sensor's transmission range such that each sensor is k-vertex supernode connected and the total power consumed by sensors is minimized. Such topologies are needed for applications that support sensor data reporting, even in the event of failures of up to k - 1 sensor nodes. We propose three solutions for the k-ATC problem: a k-approximation algorithm, a greedy centralized algorithm that minimizes the maximum transmission range between all sensors, and a distributed and localized algorithm that incrementally adjusts sensors' transmission range such that the k-vertex supernode connectivity requirement is met. Extended simulation results are presented to verify our approaches.

  • Algorithms for FaultTolerant Topology in Heterogeneous Wireless Sensor Networks
    2008
    Co-Authors: Mihaela Cardei, Shuhui Yang, Student Member, Senior Member
    Abstract:

    Abstract—This paper addresses fault-tolerant topology control in a heterogeneous wireless sensor network consisting of several resource-rich Supernodes, used for data relaying, and a large number of energy-constrained wireless sensor nodes. We introduce the k-degree Anycast Topology Control ðk-ATCÞ problem, with the objective of selecting each sensor’s transmission range such that each sensor is k-vertex supernode connected and the total power consumed by sensors is minimized. Such topologies are needed for applications that support sensor data reporting, even in the event of failures of up to k 1 sensor nodes. We propose three solutions for the k-ATC problem: a k-approximation algorithm, a greedy centralized algorithm that minimizes the maximum transmission range between all sensors, and a distributed and localized algorithm that incrementally adjusts sensors ’ transmission range such that the k-vertex supernode connectivity requirement is met. Extended simulation results are presented to verify our approaches. Index Terms—Energy efficiency, fault tolerance, heterogeneous wireless sensor networks, topology control. Ç

Mihaela Cardei - One of the best experts on this subject based on the ideXlab platform.

  • Delay-constrained energy-efficient routing in heterogeneous wireless sensor networks
    2015
    Co-Authors: Yinying Yang, Mihaela Cardei
    Abstract:

    Abstract: In this paper, we propose a routing strategy for heterogeneous wireless sensor networks, which supports both periodic and event-based reporting applications. The energy-efficient network model in this paper consists of static sensor nodes, mobile and static Supernodes. We propose an energy-efficient routing protocol that can satisfy the delay requirements of different types of data messages. Each source-sensor, with data to be transmitted to the sink, chooses the best relay supernode from the candidates in its routing table such that it meets the delay requirements. The message is transmitted to the selected relay supernode using sensor-to-sensor communication, and from there to the sink using supernode-to-supernode communication. Simulation results show that our routing protocol is energy-efficient and effectively satisfies different delay requirements

  • 1 Energy-Efficient Range Assignment in Heterogeneous Wireless Sensor Networks
    2010
    Co-Authors: Mihaela Cardei, Mohammad O. Pervaiz, Ionut Cardei
    Abstract:

    Abstract — This paper considers a heterogeneous wireless sensor network consisting of a large number of energy constrained wireless sensor nodes and a connected subnetwork of resource-rich Supernodes used for relaying sensor data to the user. We address the range assignment problem in this heterogeneous sensor network- selecting the transmission range for each sensor node such that a multihop communication path exists between each sensor node and a supernode. In order to balance power usage in the sensor network the objective of this range assignment problem is to minimize the maximum transmission power consumed at each sensor nodes. This is the first paper to address this problem. We propose several solutions: an Integer Programming approach, a distributed greedy protocol, and a minimum spanning tree protocol based on clustering. We validate and evaluate the proposed solutions with simulations. I

  • algorithms for fault tolerant topology in heterogeneous wireless sensor networks
    IEEE Transactions on Parallel and Distributed Systems, 2008
    Co-Authors: Mihaela Cardei, Shuhui Yang
    Abstract:

    This paper addresses fault-tolerant topology control in a heterogeneous wireless sensor network consisting of several resource-rich Supernodes, used for data relaying, and a large number of energy-constrained wireless sensor nodes. We introduce the k-degree anycast topology control (fc-ATC) problem, with the objective of selecting each sensor's transmission range such that each sensor is k-vertex supernode connected and the total power consumed by sensors is minimized. Such topologies are needed for applications that support sensor data reporting, even in the event of failures of up to k - 1 sensor nodes. We propose three solutions for the k-ATC problem: a k-approximation algorithm, a greedy centralized algorithm that minimizes the maximum transmission range between all sensors, and a distributed and localized algorithm that incrementally adjusts sensors' transmission range such that the k-vertex supernode connectivity requirement is met. Extended simulation results are presented to verify our approaches.

  • Algorithms for FaultTolerant Topology in Heterogeneous Wireless Sensor Networks
    2008
    Co-Authors: Mihaela Cardei, Shuhui Yang, Student Member, Senior Member
    Abstract:

    Abstract—This paper addresses fault-tolerant topology control in a heterogeneous wireless sensor network consisting of several resource-rich Supernodes, used for data relaying, and a large number of energy-constrained wireless sensor nodes. We introduce the k-degree Anycast Topology Control ðk-ATCÞ problem, with the objective of selecting each sensor’s transmission range such that each sensor is k-vertex supernode connected and the total power consumed by sensors is minimized. Such topologies are needed for applications that support sensor data reporting, even in the event of failures of up to k 1 sensor nodes. We propose three solutions for the k-ATC problem: a k-approximation algorithm, a greedy centralized algorithm that minimizes the maximum transmission range between all sensors, and a distributed and localized algorithm that incrementally adjusts sensors ’ transmission range such that the k-vertex supernode connectivity requirement is met. Extended simulation results are presented to verify our approaches. Index Terms—Energy efficiency, fault tolerance, heterogeneous wireless sensor networks, topology control. Ç

  • Energy-Efficient Target Coverage in Heterogeneous Wireless Sensor Networks
    2006
    Co-Authors: Ionut Cardei, Mihaela Cardei
    Abstract:

    This paper considers a heterogeneous wireless sensor network consisting in several resource-rich Supernodes used for data relaying and a large number of energy constrained wireless sensor nodes. Sensor nodes are deployed randomly to monitor a number of targets. Since targets are redundantly covered by more sensors, in order to conserve energy resources, we organize the sensors in set covers that are activate successively. In this paper we introduce the Heterogeneous Connected Set Covers (HCSC) problem that has as objective finding a maximum number of set covers such that each set cover monitors all targets and is connected to at least one supernode. A sensor can participate in multiple set covers, but the total energy spent in all sets is constrained by the battery capacity. In this paper we show that HCSC is NP-complete and we propose two algorithms for solving this problem, an Integer Programming approach and a distributed and localized protocol. Simulation results are presented to evaluate these solutions