Hadi Amarloo

Colorimetric sensors using nano-patch surface plasmon resonators

A two-dimensional array of gold nano-patches on a highly reflective mirror is proposed for refractive index sensing based on changes in the reflected colors. The grating on the mirror creates localized surface plasmon resonances resulting in a minimum in the visible reflectance spectra. The wavelength of the resonance can be tuned by changing the width of the nano-patches and is also dependent on the refractive index of the surrounding medium. The color variation due to change in the refractive index is measured and used to realize a simple low-cost sensor with a refractive index resolution better than 10⁻⁵ just using image processing. The efficacy of the proposed sensor is also demonstrated for surface sensing by depositing thin layers of silicon dioxide. The color difference due to the addition of a 3 nm thick layer of silicon dioxide is detectable by the naked eye and deposition thickness of 2 Å can be resolved using image processing.

Slot plasmonic waveguide based on doped-GaAs for terahertz deep-subwavelength applications.

A new plasmonic waveguide for deep-subwavelength field localization at the terahertz (THz) range of frequency is proposed. GaAs with optimum doping level is used as the plasmonic material. The waveguide structure is a narrow slot in a thin GaAs film on top of the quartz substrate. The waveguide characteristics are analyzed, and its dimensions are optimized to minimize the losses. It is shown that the mode size of the proposed waveguide is less than λ/16 by λ/16. The proposed plasmonic waveguide can be a platform for numerous THz plasmonic-based integrated devices, such as integrated sensors and imagers.

Sensitivity and error analysis of a surface plasmonic mode metallic grating sensor

The performance of a periodic metallic structure for ultra-high sensitivity of dielectric permittivity measurement at THz is presented. Of primary focus in this work are highly sub-wavelength thin samples at THz range of frequencies. The proposed periodic metallic structure is able to guide strongly confined surface plasmon-like modes, which is highly sensitive to very small change in refractive index of the medium in close proximity of the waveguide.

Terahertz Line Defect Waveguide Based on Silicon-on-Glass Technology

In this paper, based on silicon-on-glass technology, a new THz dielectric waveguide structure is proposed. The proposed waveguide is low loss, and has a mechanically stable structure. The new waveguide is scalable to higher frequencies in THz band. Theoretical and experimental results for 500 to 700 GHz frequency range are presented. The introduced waveguide can be a platform for highly sensitive integrated THz sensors.

Tunable Fano resonance in graphene based periodic structure

Engineered material have found many applications in all ranges of frequencies, because new electromagnetic properties can be achieved using these structures. Considering trasnmission of EM wave through a planar 2D periodic structure, some resonances can be seen in the transmitted signal. These resonaces have very low quality factor (Q), because the resonating elements in the structure are strongly coupled to the radiation into the free space. It has been shown that by introducing some small asymmetry in the structure, high Q resonances can be achieved. These sharp asymmetric resonances are called Fano resonances.

Multiple Fano resonace terahertz structure

A Terahertz planar periodic structure (engineered material), which shows several sharp Fano resonances, is introduce. These resonances are due to the small asymmetries of the structure which allow excitation of trapped modes. These sharp resonances can be used for biomedical sensing applications. HFSS simulation results are presented.

Colorimetric Sensors using Plasmonics Grating on a Metallic Mirror

We experimentally demonstrate a low-cost colorimetric sensor in which the change in surrounding refractive index is measured using simple image processing. This sensor consists of two-dimensional gold nanopatch grating on a highly reflective mirror.

Multiple Fano Resonances Structure for Terahertz Applications

A new planar engineered material structure, which has multiple Fano resonances at the terahertz range of frequency, is presented. Starting with a double Fano resonance structure, it is shown that by considering several unit cells as a larger unit cell and creating new asymmetries in the super- cell, we can have five Fano resonances in one structure. Analysis of current distributions at resonance frequencies clarifies the origin of different resonances. We show that all of these resonances come from different arrangement of magnetic dipoles.