scholarly journals Terahertz Guided Mode Resonance Sensing Platform Based on Freestanding Dielectric Materials: High Q-Factor and Tunable Spectrum

2020 ◽  
Vol 10 (3) ◽  
pp. 1013 ◽  
Author(s):  
Hee Jun Shin ◽  
Gyeongsik Ok
Keyword(s):  
Refractive Index ◽  
Resonance Frequency ◽  
Complex Refractive Index ◽  
Fdtd Method ◽  
Dielectric Materials ◽  
Q Factor ◽  
Guided Mode ◽  
Sensing Applications ◽  
Label Free Detection ◽  
Guided Mode Resonance

We theoretically investigated a polyethylene-based rectangular and guided mode resonance (GMR) structure with a circular pattern by using the finite-difference time-domain (FDTD) method in the terahertz region. As the refractive index of the grating decreased, the resonance frequency increased, and the Q-factor significantly increased because of the change in the effective refractive index. In addition, GMR was investigated with a sensing layer for sensing applications. The resonance frequency and Q-factor could be perfectly modulated by varying the complex refractive index and thickness of the sensing layer. These results indicate that GMR could be applied to highly sensitive label-free detection, using low-cost GMR sensing platforms based on dielectric materials.

scholarly journals Optimising the Complex Refractive Index Model for Estimating the Permittivity of Heterogeneous Concrete Models

2021 ◽  
Vol 13 (4) ◽  
pp. 723
Author(s):  
Hossain Zadhoush ◽  
Antonios Giannopoulos ◽  
Iraklis Giannakis
Keyword(s):  
Refractive Index ◽  
Shape Factor ◽  
Complex Refractive Index ◽  
Fdtd Method ◽  
Air Voids ◽  
Water Fraction ◽  
Index Model ◽  
General Complex ◽  
Ground Penetrating ◽  
Fine Tune

Estimating the permittivity of heterogeneous mixtures based on the permittivity of their components is of high importance with many applications in ground penetrating radar (GPR) and in electrodynamics-based sensing in general. Complex Refractive Index Model (CRIM) is the most mainstream approach for estimating the bulk permittivity of heterogeneous materials and has been widely applied for GPR applications. The popularity of CRIM is primarily based on its simplicity while its accuracy has never been rigorously tested. In the current study, an optimised shape factor is derived that is fine-tuned for modelling the dielectric properties of concrete. The bulk permittivity of concrete is expressed with respect to its components i.e., aggregate particles, cement particles, air-voids and volumetric water fraction. Different combinations of the above materials are accurately modelled using the Finite-Difference Time-Domain (FDTD) method. The numerically estimated bulk permittivity is then used to fine-tune the shape factor of the CRIM model. Then, using laboratory measurements it is shown that the revised CRIM model over-performs the default shape factor and provides with more accurate estimations of the bulk permittivity of concrete.

Dispersion Properties of Photonic Crystal Fibers - Issues and Opportunities

2003 ◽  
Vol 797 ◽  
Author(s):  
J. Lægsgaard ◽  
S. E. Barkou Libori ◽  
K. Hougaard ◽  
J. Riishede ◽  
T. T. Larsen ◽  
...  
Keyword(s):  
Refractive Index ◽  
Photonic Crystal ◽  
Optical Fibers ◽  
Photonic Crystal Fibers ◽  
Complex Refractive Index ◽  
Dispersion Properties ◽  
Guided Mode ◽  
Index Contrast ◽  
Mode Group ◽  
Crystal Fibers

ABSTRACTThe dispersion, which expresses the variation with wavelength of the guided-mode group velocity, is one of the most important properties of optical fibers. Photonic crystal fibers (PCFs) offer much larger flexibility than conventional fibers with respect to tailoring of the dispersion curve. This is partly due to the large refractive-index contrast available in silica/air microstructures, and partly due to the possibility of making complex refractive-index structures over the fiber cross section. We discuss the fundamental physical mechanisms determining the dispersion properties of PCFs guiding by either total internal reflection or photonic bandgap effects, and use these insights to outline design principles and generic behaviours of various types of PCFs. A number of examples from recent modeling and experimental work serve to illustrate our general conclusions.

scholarly journals Microwave Planar Sensor for Permittivity Determination of Dielectric Materials

2018 ◽  
Vol 11 (1) ◽  
pp. 362 ◽  
Author(s):  
Rammah Alahnomi ◽  
Natasha Binti Abd Hamid ◽  
Zahriladha Zakaria ◽  
Tole Sutikno ◽  
Amyrul Azuan Mohd Bahar
Keyword(s):  
Transmission Line ◽  
Resonance Frequency ◽  
Food Industry ◽  
Return Loss ◽  
Ring Resonator ◽  
Single Port ◽  
Dielectric Materials ◽  
Q Factor ◽  
Enhancement Method

<p>This paper presents a single port rectangular ring resonator sensor for material characterizations. The proposed sensor is designed at operating resonance frequency of 4 GHz. The sensor consists of micro-strip transmission line and ring resonator with applying the enhancement method to the coupling gaps. The using of enhancement method is to improve the return loss of the sensor and sensitivity in terms of Q-factor, respectively. Furthermore, the proposed sensor is designed and fabricated on Roger 5880 substrate. Standard materials with known permittivity have been used in order to validate the sensor’s sensitivity. Based on the results, the percentage of error for the proposed rectangular sensor is 0.2% to 8%. It can be demonstrated that the proposed sensor will be useful for various applications such as medicine, bio-sensing and food industry.</p>

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