scholarly journals Sensitive THz sensing based on Fano resonance in all-polymeric Bloch surface wave structure

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Chi Zhang ◽  
Qiang Liu ◽  
Xiao Peng ◽  
Zhengbiao Ouyang ◽  
Suling Shen
Keyword(s):  
Surface Wave ◽  
Quality Factor ◽  
Fano Resonance ◽  
Bound States ◽  
High Sensitivity ◽  
Influential Factors ◽  
Destructive Interference ◽  
Optimized Design ◽  
Bloch Surface Wave ◽  
The Continuum

Abstract Simultaneous realization of high quality factor (Q), sensitivity, and figure of merit (FOM) play a pivotal role in building the THz sensor. For such purpose, we propose an all-polymeric Bloch surface wave (BSW) structure that supports a bright BSW mode and a dark surface Fano state that is embedded in the continuum, both of which coupled to the same radiation channels. The existence of the sharp dip with a maximum depth of Fano line could be interpreted with the physics of Friedrich–Wintgen bound states in the continuum (FW-BICs), because of the destructive interference between bright BSW and dark surface Fano modes. A strong angular- and frequency-dependent Q was found. Related influential factors to Q value may also include an asymmetric arrangement of top and grating layers, together with the weak coupling provided by photonic crystals. One numerically optimized design shows a quality factor Q of the Fano mode as 23,670, which is almost two orders higher than that in conventional metallic-metamaterial-based designs. The optimized sensitivity can numerically reach 4.34 THz/RIU in the frequency domain, which is one order higher than that reported in all-dielectric metasurfaces. We infer the high sensitivity is related to the phase-matching condition provided by near-subwavelength gratings. The associated FOM can reach 8857/RIU. Besides, the proposed design also numerically demonstrates high sensitivity in the angular domain ∼125.5°/RIU. Considering it poses no specific requirement for materials that own high contrast of permittivity in the THz regime, large interfacing area, the mechanical and chemical robustness offered by polymers and low cost in fabrication, such all-polymeric BSW structure that supports novel Fano resonance in THz window may give access to rich applications in hazardous gas detection and label-free bio-sensing.

High-Sensitivity Bloch Surface Wave Sensor with Fano Resonance in Grating-coupled Multilayer Structures

2021 ◽  
Author(s):  
Daohan Ge ◽  
Yujie Zhou ◽  
Mengcheng Lv ◽  
Jiakang Shi ◽  
Abubakar A. Babangida ◽  
...  
Keyword(s):  
Surface Wave ◽  
Fano Resonance ◽  
High Sensitivity ◽  
Multilayer Structures ◽  
Bloch Surface Wave

scholarly journals Integrated diffraction gratings on the Bloch surface wave platform supporting bound states in the continuum

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Evgeni A. Bezus ◽  
Dmitry A. Bykov ◽  
Leonid L. Doskolovich
Keyword(s):  
Surface Wave ◽  
Bound States ◽  
Transverse Electric ◽  
Diffraction Gratings ◽  
Incidence Geometry ◽  
Spectral Filters ◽  
Beam Splitters ◽  
High Q ◽  
Bloch Surface Wave ◽  
The Continuum

Abstract We propose and theoretically and numerically investigate integrated diffraction gratings for the Bloch surface wave (BSW) platform, which have subwavelength or near-subwavelength period. We demonstrate that, in the oblique incidence geometry of a transverse-electric polarized BSW and with a properly chosen band gap configuration of the photonic crystal supporting the surface waves, the proposed structures operate in the scattering-free regime, when the energy of the incident BSW is divided between the reflected and transmitted BSWs with the same polarization corresponding to the propagating diffraction orders of the grating, and not scattered away from the propagation surface. In this regime, the studied integrated gratings support high-Q resonances and bound states in the continuum not only in the subwavelength case when only the specular (zeroth) diffraction orders propagate, but also in the case when non-evanescent zeroth and −1st diffraction orders satisfy the so-called Littrow mounting condition. The proposed integrated gratings on the BSW platform can be used as efficient narrowband spatial or spectral filters operating in reflection, or as BSW beam splitters or deflectors operating in transmission. The obtained results may find application in two-dimensional photonic circuits for steering the BSW propagation.

scholarly journals Differentiating and quantifying exosome secretion from a single cell using quasi-bound states in the continuum

Nanophotonics ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 1081-1086 ◽  
Author(s):  
Abdoulaye Ndao ◽  
Liyi Hsu ◽  
Wei Cai ◽  
Jeongho Ha ◽  
Junhee Park ◽  
...  
Keyword(s):  
Single Cell ◽  
Optical Sensors ◽  
Figure Of Merit ◽  
Bound States ◽  
Single Cell Analysis ◽  
Optical Cavity ◽  
High Sensitivity ◽  
Cell Secretion ◽  
The Continuum ◽  
Refractive Index Detection

AbstractOne of the key challenges in biology is to understand how individual cells process information and respond to perturbations. However, most of the existing single-cell analysis methods can only provide a glimpse of cell properties at specific time points and are unable to provide cell secretion and protein analysis at single-cell resolution. To address the limits of existing methods and to accelerate discoveries from single-cell studies, we propose and experimentally demonstrate a new sensor based on bound states in the continuum to quantify exosome secretion from a single cell. Our optical sensors demonstrate high-sensitivity refractive index detection. Because of the strong overlap between the medium supporting the mode and the analytes, such an optical cavity has a figure of merit of 677 and sensitivity of 440 nm/RIU. Such results facilitate technological progress for highly conducive optical sensors for different biomedical applications.

scholarly journals All-Dielectric Metasurface for Sensing Microcystin-LR

Electronics ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 1363
Author(s):  
Binze Ma ◽  
Ao Ouyang ◽  
Juechen Zhong ◽  
Pavel A. Belov ◽  
Ravindra Kumar Sinha ◽  
...  
Keyword(s):  
Quality Factor ◽  
Bound States ◽  
High Sensitivity ◽  
Concentration Limit ◽  
Specific Recognition ◽  
Low Concentrations ◽  
Freshwater Bodies ◽  
Toxic Pollutant ◽  
Small Change ◽  
Dielectric Metasurface

Sensing Microcystin-LR (MC-LR) is an important issue for environmental monitoring, as the MC-LR is a common toxic pollutant found in freshwater bodies. The demand for sensitive detection method of MC-LR at low concentrations can be addressed by metasurface-based sensors, which are feasible and highly efficient. Here, we demonstrate an all-dielectric metasurface for sensing MC-LR. Its working principle is based on quasi-bound states in the continuum mode (QBIC), and it manifests a high-quality factor and high sensitivity. The dielectric metasurface can detect a small change in the refractive index of the surrounding environment with a quality factor of ~170 and a sensitivity of ~788 nm/RIU. MC-LR can be specifically identified in mixed water with a concentration limit of as low as 0.002 μg/L by a specific recognition technique for combined antigen and antibody. Furthermore, the demonstrated detection of MC-LR can be extended to the identification and monitoring of other analytes, such as viruses, and the designed dielectric metasurface can serve as a monitor platform with high sensitivity and high specific recognition capability.

High Sensitivity Intensity-Interrogated Bloch Surface Wave Biosensor With Graphene

2018 ◽  
Vol 18 (1) ◽  
pp. 106-110 ◽  
Author(s):  
Zhitao Lin ◽  
Yue Jia ◽  
Qian Ma ◽  
Leiming Wu ◽  
Banxian Ruan ◽  
...  
Keyword(s):  
Surface Wave ◽  
High Sensitivity ◽  
Bloch Surface Wave

scholarly journals Tunable Bound States in the Continuum in All-Dielectric Terahertz Metasurfaces

Nanomaterials ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 623 ◽  
Author(s):  
Xu Chen ◽  
Wenhui Fan
Keyword(s):  
Strontium Titanate ◽  
Fano Resonance ◽  
Bound States ◽  
Cell Structure ◽  
Unit Cell ◽  
Graphene Monolayer ◽  
Quality Factors ◽  
Resonance Amplitude ◽  
Potential Applications ◽  
The Continuum

In this paper, a tunable terahertz dielectric metasurfaces consisting of split gap bars in the unit cell is proposed and theoretically demonstrated, where the sharp high-quality Fano resonance can be achieved through excitation of quasi-bound states in the continuum (quasi-BIC) by breaking in-plane symmetry of the unit cell structure. With the structural asymmetry parameter decreasing and vanishing, the calculated eigenmodes spectra demonstrate the resonance changes from Fano to symmetry-protected BIC mode, and the radiative quality factors obey the inverse square law. Moreover, combining with graphene monolayer and strontium titanate materials, the quasi-BIC Fano resonance can be tuned independently, where the resonance amplitude can be tuned by adjusting the Fermi level of graphene and the resonance frequency can be tuned by controlling the temperature of strontium titanate materials. The proposed structure has numerous potential applications on tunable devices including modulators, switches, and sensors.

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