Dual-band Sensor Research Articles

Two Individual Super-Bound State Modes within Band Gap with Ultra-High Q Factor for Potential Sensing Applications in the Terahertz Wave Band.

Bound states in the continuum (BICs) garnered significant research interest in the field of sensors due to their exceptionally high-quality factors. However, the wide-band continuum in BICs are noise to the bound states, and it is difficult to control and filter. Therefore, we constructed a top-bottom symmetric cavity containing three high permittivity rectangular columns. The cavity supports a symmetry-protected (SP) superbound state (SBS) mode and an accidental (AC) SBS mode within the bandgap. With a period size of 5 × 15, the bandgap effectively filters out the continuum, allowing only the bound states to exist. This configuration enabled us to achieve a high signal-to-noise ratio and a wide free-spectral-range. The AC SBS and the SP SBS can be converted into quasi-SBS by adjusting different parameters. Consequently, the cavity can function as a single-band sensor or a dual-band sensor. The achieved bulk sensitivity was 38 µm/RIU in terahertz wave band, and a record-high FOM reached 2.8 × 108 RIU-1. The effect of fabrication error on the performance for sensor application was also discussed, showing that the application was feasible. Moreover, for experimental realization, a 3D schematic was presented. These achievements pave the way for compact, high-sensitivity biosensing, multi-wavelength sensing, and other promising applications.

Dual-band refractive index sensor with cascaded asymmetric resonant compound grating based on bound states in the continuum.

We propose a cascaded asymmetric resonant compound grating (ARCG) for high-performance dual-band refractive index sensing. The physical mechanism of the sensor is investigated using a combination of temporal coupled-mode theory (TCMT) and ARCG eigenfrequency information, which is verified by rigorous coupled-wave analysis (RCWA). The reflection spectra can be tailored by changing the key structural parameters. And by altering the grating strip spacing, a dual-band quasi-bound state in the continuum can be achieved. The simulation results show that the highest sensitivity of the dual-band sensor is 480.1 nm/RIU, and its figure of merit is 4.01 × 105. The proposed ARCG has potential application prospects for high-performance integrated sensors.

Continuously controlling the phase transition of In3SbTe2 for tunable high quality-factors absorber

Recent progress on metasurface with high quality factors (Q-factors) based absorption of light is promising for optical filtering and sensing. However, most reported metasurface-based absorbers are suffering from limited bandwidth due to the single mode and non-reconfiguration features, which have greatly restricted their practical applications. Herein, we propose a tunable absorber with high Q-factors combined with the phase-change materials (PCM) In3SbTe2 (IST), whose optical properties can change from dielectric to metallic upon crystallization in the whole infrared spectral range. Moreover, we investigate the dual-band resonant modes separately. The Q-factors of the proposed dual-band perfect absorber are both greater than 1200 when the IST is amorphous state, which can be attributed to the low radiative loss of the guide-mode resonances and low intrinsic loss of the constituent materials. Hence, the proposed high Q-factors absorber is the best candidate for a sensitive refractive index sensor since its corresponding absorption spectrum changes significantly with the slight change of the refractive index of surrounding mediums. Our dual-band sensor scheme shows extreme spectral sensitivity with respect to the refractive index change to be 185.2 nm/RIU and 57.2 nm/RIU with a figure of merit of 84.2 and 22.9, respectively. Furthermore, by controlling the phase transition in IST, we further proved that the proposed absorber can be modulated continuously due to the non-volatile property of IST. Overall, the proposed dual-band absorber provides an alternative and simple pathway for the construction of dynamic and multifunctional optical devices, such as optical modulators, tunable multiband filters and biochemical sensors.

Dual-Band Uniaxial Dielectric Anisotropy Sensor Using Coupled-Line Resonators

In this paper, a new dual-band sensor to measure uniaxial anisotropy at two frequency bands is proposed. This sensor is composed of two dual-mode resonators separated by a T-shaped structure implemented in microstrip technology. The configuration of vertical and horizontal electric field lines for the two resonance modes allows for the characterization of a uniaxial anisotropic sample placed on top of the sensor. The resonance frequencies of different modes are separated using active S-parameters measured at the input port. They are subsequently used in the space mapping process to extract the dielectric constants of the sample in two directions, parallel and normal to the surface of the sensor, by means of electromagnetic analyses. The sensor is used to extract the dielectric constants of anisotropic FR4, RO4003C, and RO3010 samples at 2.4 and 3.4 GHz. An isotropic PTFE sample is also characterized to verify the reliability of the proposed method. Two single-band sensors are also implemented to measure RO3010 sample and the extracted dielectric constants are compared to those resulted from the proposed dual-band sensor.

Metamaterial-based terahertz dual-band sensor integrated with microfluidic channels

We present the design of an innovative dual-band terahertz sensor based on a metamaterial array and a microfluidic channel. The sensing performance of two ultra-high absorption peaks—with absorption rates of 99.96% and 99.85%—generated in the frequency band of 0.2 to 1.2 THz is analyzed. Refractive indexes of analytes are predicted to be in a specific refractive index range, demonstrating the very low prediction error rate of the proposed sensor. Further analyses show that the designed sensor has application potential in label-free and rapid detection.

Characterization of Dielectric Substrates Using Dual Band Microwave Sensor

In this work, a compact, inexpensive, and efficient dual band microwave sensor is proposed. The sensor is based on two Complementary Symmetric Split-Ring Resonators (CSSRRs) and possesses a high $Q$ factor and wide sensing range. These CSSRRs are coupled electrically with two inductive patches to the Microstrip Transmission Line (MTL). This combination provides two dual bands, first at 5.35 GHz with a notch depth of -55.20 dB and second at 7.99 GHz with a notch depth of -22.54 dB. The sensor works in transmission mode and senses shift in frequency. Some commonly available dielectric substrates with relative permittivity ranges between 1 and 12 are considered Material Under Test (MUT), and detailed sensitivity analysis is being performed for each band. The dual band sensor is fabricated on a low-cost, widely available FR4 substrate and measured by CEYEAR AV3672D vector network analyzer. Additionally, the least square curve fitting method is used to develop a mathematical model for the measured results. An excellent agreement is observed between simulated, measured, and formulated results.

Design of frequency controlled 4G and 5G band dielectric sensors using cross-polarized metamaterial particle dedicated to communication industry

ABSTRACTA novel approach is presented to design the dual-band planar sensor for the communication system. The proposed sensor is based on the complementary split ring resonator (CSRR) topology employing the cross-polarized excitation, which facilitates its operation even at the higher frequency band (28 GHz). The cross-polarized excitation of a CSRR allows efficient coupling of both electric and magnetic fields from the microstrip line, thereby producing the frequency-controlled dual resonance response. The prime focus here is to use the proposed approach to design two sensors with one sensor being simultaneously operated in the X-band and 5G band, while another sensor is operated in the 4G LTE band. The cross-polarized arrangement helps to achieve the higher dielectric sensitivity (17.21%) and Q factor (90) as compared to that of the co-polarized CSRR-loaded microstrip line sensor (14%, 73), where split of rings is aligned in the direction orthogonal to the microstrip line.

Dual band RF sensor for testing of magnetic properties of materials using meandered line SRR

In this paper, a microwave planar resonant sensor using the meandered line based split ring resonator (MLSRR) is proposed to retrieve the magnetic properties of materials in 3G and 4G GSM bands. The proposed sensor is based on the field perturbation theory, where the permeability of the test sample is determined after placing it on the designed meandered conductive loop. The loading of magnetic test sample on the meandered conductive loop of the split ring resonator perturbs the magnetic field concentrated on it thereby changing the resonant frequency of the sensor, which is recorded for the determination of permeability. The proposed dual band RF sensor is designed using the full wave electromagnetic solver. The equivalent circuit model and the corresponding numerical model of the proposed dual band sensor are discussed. The designed sensor is fabricated using the standard microstrip technology. The resonant frequencies of the proposed sensor are measured using the vector network analyzer (VNA), and are found to be 1.71 GHz and 2.35 GHz corresponding to 3G and 4G bands, respectively. Various standard materials are measured and the relative permeability is estimated using the proposed sensor in combination with the developed numerical model. The measured data are compared with values available in literature, and the typical error is found to be less than 8% for all the samples.

High-sensitive dual-band sensor based on microsize circular ring complementary terahertz metamaterial

Recently, resonance sensing based on the terahertz metamaterials has attracted considerable attentions due to the enhancement and confinement of local fields in microsize gap of resonant structures. Here, a high-sensitive dual-band sensor based on the complementary terahertz metamaterial composed of microsize circular ring gap array is proposed to detect the thickness and refractive index of thin film. The structure of this sensor is polarization insensitive dual-band operating mode and can be easily filled by the biomolecules. Simulation results demonstrate that the dual-band resonances are very sensitive to the dielectric variation, and the sensitivity levels of 99 GHz/refractive index unit (RIU) for mode f1 and 242 GHz/RIU for mode f2 are obtained and further enhanced by optimizing structures. Therefore, this structure can exhibit promising application for monitoring thin film thickness.

Dual-Band Sensor Network for Accurate Device-Free Localization in Indoor Environment with WiFi Interference

Dual-Band Sensor Network for Accurate Device-Free Localization in Indoor Environment with WiFi Interference