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Single Nanoparticle Detection Using Far-field Emission of Photonic Molecule around the Exceptional Point.

Zhang N, Liu S, Wang K, Gu Z, Li M, Yi N, Xiao S, Song Q - Sci Rep (2015)

Bottom Line: In addition to typical mode splitting, we find that the far-field pattern of the PM is significantly changed.Taking a heteronuclear diatomic PM as an example, we demonstrate that a single nanoparticle, whose radius is as small as 1 nm to 7 nm, can be simply monitored through the variation of the far-field pattern.In addition, this research will illuminate new advances in single nanoparticle detection.

View Article: PubMed Central - PubMed

Affiliation: Integrated Nanoscience Lab, Department of Electrical and Information Engineering, Harbin Institute of Technology, Shenzhen, 518055, China.

ABSTRACT
Highly sensitive, label-free detection methods have important applications in fundamental research and healthcare diagnostics. To date, the detection of single nanoparticles has remained largely dependent on extremely precise spectral measurement, which relies on high-cost equipment. Here, we demonstrate a simple but very nontrivial mechanism for the label-free sizing of nanoparticles using the far-field emission of a photonic molecule (PM) around an exceptional point (EP). By attaching a nanoparticle to a PM around an EP, the main resonant behaviors are strongly disturbed. In addition to typical mode splitting, we find that the far-field pattern of the PM is significantly changed. Taking a heteronuclear diatomic PM as an example, we demonstrate that a single nanoparticle, whose radius is as small as 1 nm to 7 nm, can be simply monitored through the variation of the far-field pattern. Compared with conventional methods, our approach is much easier and does not rely on high-cost equipment. In addition, this research will illuminate new advances in single nanoparticle detection.

No MeSH data available.


Near-field distribution of resonance mode at KR~4.3436โ€“0.001086i.(a) Without target particle. A target particle at ฮฒ2โ€‰=โ€‰0 with the radius r2โ€‰=โ€‰2โ€‰nm (b), r2โ€‰=โ€‰3โ€‰nm (c), and r2โ€‰=โ€‰4โ€‰nm (d).
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f2: Near-field distribution of resonance mode at KR~4.3436โ€“0.001086i.(a) Without target particle. A target particle at ฮฒ2โ€‰=โ€‰0 with the radius r2โ€‰=โ€‰2โ€‰nm (b), r2โ€‰=โ€‰3โ€‰nm (c), and r2โ€‰=โ€‰4โ€‰nm (d).

Mentions: Then, we numerically calculate the resonant properties of TE (transverse electric) modes by solving Maxwellโ€™s equations using the effective index approximation42. The refractive indices of the PM and nanoparticle are 3.3 (for GaAs or silicon) and 1.5 (for polystyrene). The external environment is set at nโ€‰=โ€‰1, following the experiment presented in Ref. 24. Figure 2 shows the field patterns of modes with the azimuthal number mโ€‰=โ€‰10 and the radial number lโ€‰=โ€‰1. Without external perturbation, the field distribution inside the circular cavity is quite uniform, which reflects the fact that the modes near EP are traveling waves rather than standing waves. When a target particle is placed near the circular cavity, the field distributions gradually change. As shown in Fig. 2(b), a visible nodal line starts to appear and becomes very apparent when the particle size is r2โ€‰=โ€‰4โ€‰nm (see Fig. 2(d)), which means that the modes inside the cavity turn from propagating waves to partially standing waves and that the resonant modes have been gradually pushed away from the EP. The standing waves are formed by the interference between the CW propagating waves and the scattered waves along the CCW direction. As mentioned above, the interference redistributes the field. Because the modes are still close to the EP, it is difficult to separate the symmetric mode (SM) and anti-symmetric mode (ASM), as is done in conventional studies24. Below, we define SM and ASM as the modes with relatively stronger and weaker field distributions inside and around the nanoparticle, respectively.


Single Nanoparticle Detection Using Far-field Emission of Photonic Molecule around the Exceptional Point.

Zhang N, Liu S, Wang K, Gu Z, Li M, Yi N, Xiao S, Song Q - Sci Rep (2015)

Near-field distribution of resonance mode at KR~4.3436โ€“0.001086i.(a) Without target particle. A target particle at ฮฒ2โ€‰=โ€‰0 with the radius r2โ€‰=โ€‰2โ€‰nm (b), r2โ€‰=โ€‰3โ€‰nm (c), and r2โ€‰=โ€‰4โ€‰nm (d).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493635&req=5

f2: Near-field distribution of resonance mode at KR~4.3436โ€“0.001086i.(a) Without target particle. A target particle at ฮฒ2โ€‰=โ€‰0 with the radius r2โ€‰=โ€‰2โ€‰nm (b), r2โ€‰=โ€‰3โ€‰nm (c), and r2โ€‰=โ€‰4โ€‰nm (d).
Mentions: Then, we numerically calculate the resonant properties of TE (transverse electric) modes by solving Maxwellโ€™s equations using the effective index approximation42. The refractive indices of the PM and nanoparticle are 3.3 (for GaAs or silicon) and 1.5 (for polystyrene). The external environment is set at nโ€‰=โ€‰1, following the experiment presented in Ref. 24. Figure 2 shows the field patterns of modes with the azimuthal number mโ€‰=โ€‰10 and the radial number lโ€‰=โ€‰1. Without external perturbation, the field distribution inside the circular cavity is quite uniform, which reflects the fact that the modes near EP are traveling waves rather than standing waves. When a target particle is placed near the circular cavity, the field distributions gradually change. As shown in Fig. 2(b), a visible nodal line starts to appear and becomes very apparent when the particle size is r2โ€‰=โ€‰4โ€‰nm (see Fig. 2(d)), which means that the modes inside the cavity turn from propagating waves to partially standing waves and that the resonant modes have been gradually pushed away from the EP. The standing waves are formed by the interference between the CW propagating waves and the scattered waves along the CCW direction. As mentioned above, the interference redistributes the field. Because the modes are still close to the EP, it is difficult to separate the symmetric mode (SM) and anti-symmetric mode (ASM), as is done in conventional studies24. Below, we define SM and ASM as the modes with relatively stronger and weaker field distributions inside and around the nanoparticle, respectively.

Bottom Line: In addition to typical mode splitting, we find that the far-field pattern of the PM is significantly changed.Taking a heteronuclear diatomic PM as an example, we demonstrate that a single nanoparticle, whose radius is as small as 1 nm to 7 nm, can be simply monitored through the variation of the far-field pattern.In addition, this research will illuminate new advances in single nanoparticle detection.

View Article: PubMed Central - PubMed

Affiliation: Integrated Nanoscience Lab, Department of Electrical and Information Engineering, Harbin Institute of Technology, Shenzhen, 518055, China.

ABSTRACT
Highly sensitive, label-free detection methods have important applications in fundamental research and healthcare diagnostics. To date, the detection of single nanoparticles has remained largely dependent on extremely precise spectral measurement, which relies on high-cost equipment. Here, we demonstrate a simple but very nontrivial mechanism for the label-free sizing of nanoparticles using the far-field emission of a photonic molecule (PM) around an exceptional point (EP). By attaching a nanoparticle to a PM around an EP, the main resonant behaviors are strongly disturbed. In addition to typical mode splitting, we find that the far-field pattern of the PM is significantly changed. Taking a heteronuclear diatomic PM as an example, we demonstrate that a single nanoparticle, whose radius is as small as 1 nm to 7 nm, can be simply monitored through the variation of the far-field pattern. Compared with conventional methods, our approach is much easier and does not rely on high-cost equipment. In addition, this research will illuminate new advances in single nanoparticle detection.

No MeSH data available.