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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.


The resonant frequencies and Q factors of SM (red circles) and ASM (squares) as a function of nanoparticle size.
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f4: The resonant frequencies and Q factors of SM (red circles) and ASM (squares) as a function of nanoparticle size.

Mentions: The important question is how such directionality is affected by the target particle. The most intuitive expectation is that the unidirectional emission of the initial mode is “diluted” by the multiple directional emissions caused by the scattering at the nanoparticle. To verify this possibility, we have studied the resonant behaviors of the hybrid modes in PM. As shown in Fig. 4, with increasing particle size, both SM and ASM shift to smaller frequencies, similar to conventional studies. However, the behaviors of Q factors are quite different. The Q factor of ASM, which receives less influence from the nanoparticle, is slightly reduced, by approximately 20%. The Q factor of SM first increases and then decreases slightly. The response of SM’s Q factor, particularly the increase in the Q factor, contradicts the conventional understanding. Following the intuitive configuration, strongly scattering light to the far field induces a larger loss and thus reduces the Q factors. Thus, the scattering to the far field is not the main mechanism for the degradation of the U factor.


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)

The resonant frequencies and Q factors of SM (red circles) and ASM (squares) as a function of nanoparticle size.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: The resonant frequencies and Q factors of SM (red circles) and ASM (squares) as a function of nanoparticle size.
Mentions: The important question is how such directionality is affected by the target particle. The most intuitive expectation is that the unidirectional emission of the initial mode is “diluted” by the multiple directional emissions caused by the scattering at the nanoparticle. To verify this possibility, we have studied the resonant behaviors of the hybrid modes in PM. As shown in Fig. 4, with increasing particle size, both SM and ASM shift to smaller frequencies, similar to conventional studies. However, the behaviors of Q factors are quite different. The Q factor of ASM, which receives less influence from the nanoparticle, is slightly reduced, by approximately 20%. The Q factor of SM first increases and then decreases slightly. The response of SM’s Q factor, particularly the increase in the Q factor, contradicts the conventional understanding. Following the intuitive configuration, strongly scattering light to the far field induces a larger loss and thus reduces the Q factors. Thus, the scattering to the far field is not the main mechanism for the degradation of the U factor.

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.