Maryam Bazgir’s research while affiliated with Lorestan University and other places

This article describes the development of a microwave sensor with a high Q-factor for measuring permittivity. The compact size of the sensor is deemed essential, leading to the utilization of a coupled line with two coupled split-ring resonators (SRRs) as the main section of this sensor. The coupling between the SRR and two transmission line resonators creates a trap for the electrical field, forming a hot spot and resulting in a high Q-factor sensor. To further improve the Q-factor, the electric inductive capacitive (ELC) element in the ground layer is utilized. However, losses due to the dielectric and surface wave effects are common problems faced in obtaining optimal results. To address these challenges, electromagnetic band gap (EBG) unit-cells are used as metasurfaces to enclose the main sensor element. This set-up establishes an electromagnetic shield, minimizing losses and improving the overall performance of the sensor. The sensor is specifically tuned to operate at 3.36 GHz. The study employs simulation using the finite element method (FEM) and compares the results with experimental data. The material under test (MUT) in this study is FR-4 substrates with photonic band gap (PBG) properties, having a permittivity range from 2 to 4.2. The obtained outcomes are then compared with the effective permittivity derived from the Maxwell–Garnett equation. The measured average sensitivity ( ${S}_{\text {avg}}$ ) of the developed sensor is determined to be 4.68%. Despite its high sensitivity, the sensor maintains a compact size, with total dimensions of $0.4\lambda _{{0}} \times 0.4\lambda _{{0}}$ , where $\lambda _{{0}}$ represents the free-space wavelength at the operating frequency.

This paper presents the development of a microwave sensor designed to measure the permittivity of liquids using a novel slow-wave transmission line (SWTL) integrated with a composite right-left-hand (CRLH) element to achieve a Fano response and precise phase control. The incorporation of the SWTL significantly enhances the sensor’s performance, leading to a higher Q-factor and improved sensitivity compared to a conventional sensor design. Notably, the Q-factor of the sensor’s second resonance increases from 52.2 to 88.3 with the implementation of SWTL. The sensor demonstrates dual-band operation at 4.6 GHz and 5.2 GHz, exhibiting a distinct Fano resonance. Moreover, the SWTL improves the electric field concentration within the interdigital capacitance, which acts as the unit-cell’s hot spot. The fabricated sensor measures the density of dissolved glucose in pure water, using polyamide tubes as loop-shaped holders filled with varying glucose concentrations. Sensitivity is evaluated based on both simulation and experimental results.

The perfect absorber with high figure of merit (FOM) and sensitivity for mid-infrared application is developed in this study. The structure contains a nanoaperture as a resonator and multi-layer hyperbolic metamaterial of graphene-SiN is place under the nanoaperture to increasing the absorption. The results show how the chemical potential of graphene can improve the absorbance. Finally, a coat of SiO2 is pinpointed over the nanoaperture for enhance the absorption and protecting the surface. The proposed aperture is designed symmetrically based on crossed shape to reduce the polarization effects on sensing. The Q-factor has increased sharply to 3000 for the final device by utilizing the hyperbolic material structure. The left-hand characteristic of the hyperbolic metamaterial provides a condition for concentrating the surface Plasmon’s at the interface of the gold layer with the substrate, leading to the reflection reduction to -46 dB. This absorber is considered as an optical sensor for various materials under test (MUT) in the optical spectrum and it is simulated by FIT method as a time-domain technique. This sensor has a sensitivity of 400 nm/RIU and the FOM of 89000 RIU⁻¹.

In this work, we design a plasmonic metasurface as an optical refractive index sensor with high sensitivity and switching characteristics for the mid-infrared spectral region by employing organic material with reconfigurable attributes. This structure contains a cross element at the center which is surrounded by a frame with four similar rectangular parasitic elements at each corner. The parasitic elements as plasmonic absorbers are exploited for concentrating energy and reducing the reflection from the metasurface. This plasmonic absorber is utilized to improve the figure of merit (FOM) and sensitivity of the sensor because of the semi-Fano characteristic of the reflection response. Organic materials are being employed in this technique to design the absorber due to their distinct switching characteristics inside the gaps between the parasitic elements and cross frame which can be considered for controlling electric field distribution and reflection of the metasurface. The use of organic materials reduces the reflection of the metasurface about −11 dB in comparison to the primary model without organic material. In fact, the equivalent circuit and electric field can be highlighted to describe the features of this absorber and the DNA load effects. The switching ratio is obtained 42 times, and this absorber is modified for 110 THz with a reflection of −32 dB, and the FOM obtained for the sensor is 51 RIU−1, with linear variation and sensitivity of 2440 nm/RIU.

The intent of this paper is to design of a nanoantenna with Fano response, by using a split ring resonator (SRR) element as a refractive index sensor in the range of 2 – 4μm for the infrared spectrum. A few organic material particles are implanted inside of the gaps which are made by the gold layers so that using organic materials conduce to the switchable characteristic in this nanoantenna. The gaps play a fundamental role to control the electric field and create hot spots at the center of the proposed nanoantenna. The primary antenna shows Fano response at 2450 nm and 3100 nm and the parasitic elements are added to this primary nanoantenna. The parasitic elements are important to control the electric fields in hot spots and change the shape of Fano response in the second nanoantenna. The extinction cross-section (ECS) and the electric field of the antenna are compared for both “On” and “Off” modes of the switches. It shows the organic material particles’ conductivity can be noticed to design a switchable nanoantenna thereby it is suitable to be exploited as an optical sensor. The sensitivity of both suggested structures is obtained from frequency shift and ECS change with a maximum value of 420 nm/RIU and 4.93×105 nm2/RIU.

A switchable surface plasmon polariton optical coupled waveguide made by exploiting a DNA composite is proposed in this paper. The switchable DNA element is used for controlling the electric field and transmission line shape. A multiband resonance is obtained for transmission to improve the optical sensing performance. Here, dumbbell-shaped cavity slots are utilized to control the effective length, with two resonances at 960 and 1260 nm for the low-conductivity mode, while there is one peak at 1590 nm for the high-conductivity mode. The DNA element is placed between two conductive silver lines, and thus acts as a switch. The structure can be controlled by switching between the DNA composite conductivity modes, and this ability can be considered for optical gates or switches at 960 and 1500 nm. The resulting switching factor is about 450 at 960 nm. The frequency shift and variation in full width at half maximum are evaluated as two functions for obtaining the sensitivity and figure of merit (FOM) of the refractive index. Therefore, this optical waveguide can be used both as an optical switch and as a refractive index (RI) sensor, with sensitivity of about 1260 nm/RIU and FOM of 120 RIU−1.

Recently, organic materials, such as proteins, have been considered as switchable materials for optical applications, such as optical gates. We exploited an organic material layer for new applications in optical absorbers. We also employed a heptamer disk array as our unit cell, with each disk comprising an organic material and a gold layer. We controlled the conductivity of the organic material by biasing the gold electrode. The absorber provided switchable absorption characteristics in the optical regime. In this letter, we considered “ON” and “OFF” modes for the organic layer. The organic disks have been selectively set to either the “ON” or the “OFF” mode. We demonstrated a reconfigurable absorber in the 170–200-THz range that is useful for optical sensing by fiber optics. Switching operations have affected the electric field distribution and surface plasmon distribution.