Aya Zaki

Integrated optical sensor using hybrid plasmonics for lab on chip applications

We propose a novel, compact plasmonic sensing structure based on a metal–insulator–metal waveguide hybridly-coupled to a rectangular side cavity. The structure has been numerically investigated using the finite-difference time-domain method. Transmission spectra obtained from numerical simulations are used to analyze the sensing characteristics of the structure. The effects of the geometrical parameters on transmission and sensing of the structure are studied. With optimum design, sensitivity can reach as high as 1500 nm per refractive-index unit around the resonance wavelength of 1550 nm with a cavity area of 1 μm2. The proposed structure can potentially be applied in on-chip pressure and gas micro-sensors.

High Sensitivity Hybrid Plasmonic Rectangular Resonator for Gas Sensing Applications

A compact plasmonic rectangular sensor of effective fabrication cost is proposed. A hybrid coupling mechanism is utilized. The structure is optimized using numerical simulations. A high sensitivity of 1385 nm/RIU is reached at wavelength of 1.55 μm.

Low power compact hybrid plasmonic double microring electro-optical modulator

In this work, we present an electro-optical modulator based on electromagnetically induced transparency (EIT). Our modulator employs a conductor-gap-silicon (CGS) microring resonator on each side of the input waveguide in a pushpull configuration utilizing an embedded electro-optical polymer (EOP). CGS waveguides support hybrid plasmonic modes offering a sound trade-off between mode confinement and propagation loss. The modulator is designed and analyzed using 3D finite difference time domain (FDTD) simulations. To have a high quality resonator, the rings are designed to have moderate waveguide propagation losses and a sub-micron radius of R = 805 nm. With an exact capacitance of just 1.06 fF per single microring resonator and applied voltage of 2 V, the exact energy consumption is estimated to be 4.24 fJ/bit. To the best of our knowledge, this figure represents 40% less power consumption in comparison with different modulators structures. The ultra-small capacitance of the proposed modulator and the instantaneous response of the used polymer make our design suitable for high bit rate applications. At the wavelength of -1550 nm-, the insertion loss is 0.34 dB and the extinction ratio is 10.23 dB.

Integrated lab-on-a-chip sensor using shallow silicon waveguide multimode interference (MMI) device

The objective of this work was to develop an integrated general purpose label-free optical sensor using standard photolithography on silicon-on-insulator platform for lab on chip applications. Shallow silicon waveguides have weak confinement in the silicon with lots of field in the cladding. This is advantageous in sensor applications due to the high light matter interaction. Here, we use our shallow strip waveguide platform to design a sensor employing a multimode interference (MMI) section. Utilizing a multi-mode section as short as 4 mm, the sensor exhibits sensitivity ranging from 417 nm / RIU to 427 nm / RIU with a figure of merit from 32 to 133.

Comprehensive Survey on Dynamic Graph Models

Most of the critical real-world networks are con-tinuously changing and evolving with time. Motivated by the growing importance and widespread impact of this type of networks, the dynamic nature of these networks have gained a lot of attention. Because of their intrinsic and special characteristics, these networks are best represented by dynamic graph models. To cope with their evolving nature, the representation model must keep the historical information of the network along with its temporal time. Storing such amount of data, poses many problems from the perspective of dynamic graph data management. This survey provides an in-depth overview on dynamic graph related problems. Novel categorization and classification of the state of the art dynamic graph models are also presented in a systematic and comprehensive way. Finally, we discuss dynamic graph processing including the output representation of its algorithms.

Silicon photonic mid-infrared grating coupler based on silicon-on-insulator technology

A novel vertical grating coupler design and optimization is presented to enable coupling of mid-infrared light into silicon-on-insulator integrated optical gas sensor circuit. The target wavelength is around 3100 nm, where the acetylene gas and a group of hydrocarbons possess a strong absorption. The grating coupler dimensions are optimized according to the limits of a standard and low-cost fabrication technology for silicon on silica by Interuniversity Micro Electronics Center (IMEC). The design simulations were carried out using 2D and 3D finite difference time domain simulation in the mid-infrared. The optimized coupling efficiency is found to be approximately 10% and the 3-dB bandwidth of the coupler is approximately 160 nm depending on the grating fill factor. The reported bandwidth is compatible with the gas sensing application

Hybrid plamonic conductor-gap-silicon microring-on-disks electro-optic modulator

In this work, we propose a novel design of a double microring-on-disk electro-optic modulator based on hybrid plasmonic conductor-gap-silicon platform utilizing the electromagnetic induced transparency response. The modulator can be realized using relatively simple fabrication processes and has a very low power consumption of about 2.12 fJ/bit.

Silicon plasmonic microring modulator using embedded conducting oxides

Silicon photonics offer a promising solution to high speed chip-to-chip interconnects implied by the next generation of computing and communication systems. Electro-optical modulators are the key devices enabling data to be imparted onto an optical carrier wave to propagate in silicon photonic links. Modulators that utilize transparent conducting oxides as the electro-optical active layer in hybrid plasmonic waveguides have recently received a lot of attention. However, no study has considered embedding the conducting oxide in hybrid plasmonic ring and disk structures. In this paper, we propose a novel hybrid plasmonic micro-ring modulator employing an indium-tin-oxide (ITO) layer on silicon-on-insulator (SOI) platform. A pure standard silicon access waveguide is introduced and a detailed discussion of the coupling junction design is presented. Due to its unique electro-optical properties, a unity order change in the refractive index of ITO is attainable and exploited to make a significant shift in the resonance wavelength eliminating the need for high quality factor resonance without sacrificing power consumption. Unlike conventional ring modulators, the proposed modulation mechanism uses the combined effect of changes in both the real and the imaginary parts of the refractive index to control the resonance wavelength and extinction ratio. We comprehensively study the modulator performance and the transmission spectra using FDTD simulations. Optimization of the design leads to a high modulation depth of about 20 dB for an applied voltage of 2V. The design has an estimated total capacitance less than 2 fF.

Metal-capped silicon organic micro-ring electro-optical modulator (Conference Presentation)

An ultra-compact hybrid plasmonic waveguide ring electro-optical modulator is designed to be easily fabricated on silicon on insulator (SOI) substrates using standard silicon photonics technology. The proposed waveguide is based on a buried standard silicon waveguide of height 220 nm topped with polymer and metal. The key advantage of this novel design is that only the silicon layer of the waveguide is structured as a coupled ring resonator. Then, the device is covered with electro-optical polymer and metal in post processes with no need for lithography or accurate mask alignment techniques. The simple fabrication method imposes many design challenges to obtain a resonator of reasonable loaded quality factor and high extinction ratio. Here, the performance of the resonator is optimized in the telecom wavelength range around 1550 nm using 3D FDTD simulations. The design of the coupling junction between the access waveguide and the tightly bent ring is thoroughly studied. The extension of the metal over the coupling region is exploited to make the critical dimension of the design geometry at least 2.5 times larger than conventional plasmonic resonators and the design is thus more robust. In this paper, we demonstrate an electro-optical modulator that offers an insertion loss < 1 dB, a modulation depth of ~12 dB for an applied peak to peak voltage of only 2 V and energy consumption of ~1.74 fJ/bit. The performance is superior to previously reported hybrid plasmonic ring resonator based modulators while the design shows robustness and low fabrication cost.

Low power hybrid plasmonic microring-on-disks electro-optical modulators

Abstract. Different electro-optical modulator designs based on electromagnetically induced transparency are proposed. A conductor–gap–silicon input waveguide is coupled to microrings-on-disks on each side. A low voltage modulating signal is applied to the modulator in a push-pull configuration, which changes the refractive index of the embedded layer of the electro-optical polymer. The proposed microrings-on-disks and cascaded microring modulators with submicron radii can efficiently modulate the light wave with moderate propagation losses. The microring-on-disk modulator achieved ultrasmall capacitance, 1.06 fF, and low power consumption, 2.12  fJ/bit. Both modulators have low insertion losses and high extinction ratios.