Amplified molecular detection sensitivity in passive dielectric cavity

He, De; Guo, Shixing; Liu, Lu; Zhang, Tieyan; Jiang, Yadong; Xu, Jimmy; Liu, Zhijun

doi:10.1364/oe.26.032026

Cited by 3 publications

(3 citation statements)

References 29 publications

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“…In addition to plasmonic metal particles or structures, local fields can also be enhanced by interference effects. Accordingly, interference can also be used to enhance the signals of analytes, as it has recently been rediscovered. − Unfortunately, interference also leads to undesired effects in spectra, which are commonly referred to as “interference fringes”. Typically, these appear as wave-like background in the spectra, e.g., in case of thin films placed on transparent substrates, if there is a mismatch between the index of refraction of the substrate and the film in nonabsorbing spectral regions.…”

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confidence: 99%

CaF₂: An Ideal Substrate Material for Infrared Spectroscopy?

et al. 2020

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CaF 2 seems to be the ideal substrate material for the infrared spectroscopy of organic and biological layers, since its refractive index is very similar to that of these materials. As a consequence of this similarity, the baseline, i.e., the signal strength in nonabsorbing regions, is nearly flat and does not show notable interference fringes. Nevertheless, as absorption is always accompanied by changes of the refractive index, the refractive indices of substrate and layer can substantially deviate around absorption bands. As a consequence, changes in band intensity, shape, and position result, which aggravate a correct interpretation of the spectra. For layers with thicknesses between 1 and 2 μm, we show experimentally, that deviations from the Beer−Lambert law of up to ±10% occur. Calculations reveal that for thinner layers these deviations are even higher. These results suggest the application of a wave-optics based formalism to correct the deviations. We introduce such a formalism and prove that it is able to remove the errors. In addition, it also corrects band shape and position changes.

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confidence: 99%

CaF₂: An Ideal Substrate Material for Infrared Spectroscopy?

et al. 2020

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“…To add ODT molecules as the analyte, the fabricated sample was immersed in 1 mM/L ODT (>95%, Sigma-Aldrich, St. Louis, MO, USA) in ethanol solution for 24 hours at room temperature, and then rinsed thoroughly with ethanol and dried with nitrogen gas. In the self-assembling process, ODT molecules form a monolayer on surfaces of both Au strips and the ZnSe layer [34][35][36]. A SEM image of the sample with monolayer ODT is shown in Figure 1c.…”

Section: Methodsmentioning

confidence: 99%

“…Sci. 2019, 9, the ZnSe layer [34][35][36]. A SEM image of the sample with monolayer ODT is shown in Figure 1c.…”

Section: Methodsmentioning

confidence: 99%

Refractive Index Sensing of Monolayer Molecules Using Both Local and Propagating Surface Plasmons in Mid-Infrared Metagrating

Zhang

Liu

et al. 2019

Applied Sciences

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Surface-enhanced infrared absorption spectroscopy (SEIRA) is attractive for molecular sensing due to its high sensitivity and access to molecular fingerprint absorptions. In this paper, we report on refractive index sensing of monolayer molecules in a spectral band outside the molecular fingerprint region. In a metagrating composed of a three-layer metal-insulator-metal structure, both propagating surface plasmon resonances (PSPs) and local surface plasmon resonances (LSPRs) are exited from free-space in a broad band of 3 to 9 µm, and their sensing properties are characterized. In response to a self-assembled monolayer of octadecanethiol (ODT) molecules, both PSPs and LSPRs exhibit redshifts in wavelength. The shifts of LSPRs are larger than those of PSPs, as originated from their stronger spatial confinement and larger field enhancement. Our proposed mid-infrared molecular sensor is immune to frequency variations of plasmon resonance and more tolerant to sample feature size variation.

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Structures for surface-enhanced nonplasmonic or hybrid spectroscopy

2020

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Absorption, scattering, and fluorescence are processes that increase with electric field intensity. The most prominent way to enhance electric field intensity is to use localized or propagating surface plasmon polaritons (SPPs) based on metallic particles and nanostructures. In addition, several other, much less well-known, photonic structures that increase electric field intensity exist. Interference enhancement provided by thin dielectric coatings on reflective substrates is able to provide electric field intensity enhancement over the whole substrate and not only at certain hotspots, thereby being in particular suitable for the spectroscopy of thin surface layers. The same coatings on high refractive index substrates may be used for interference-enhanced total internal reflection-based spectroscopy in much the same way as Kretschmann or Otto configuration for exciting propagating SPPs. The latter configurations can also be used to launch Bloch surface waves on 1D photonic crystal structures for the enhancement of electric field intensity and thereby absorption, scattering, and fluorescence-based spectroscopies. High refractive index substrates alone can also, when nanostructured, enhance infrared absorption or Raman scattering via Mie-type resonances. As a further method, this review will cover recent developments to employ phonon polaritons in the reststrahlen region.

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Amplified molecular detection sensitivity in passive dielectric cavity

Cited by 3 publications

References 29 publications

CaF₂: An Ideal Substrate Material for Infrared Spectroscopy?

CaF₂: An Ideal Substrate Material for Infrared Spectroscopy?

Refractive Index Sensing of Monolayer Molecules Using Both Local and Propagating Surface Plasmons in Mid-Infrared Metagrating

Structures for surface-enhanced nonplasmonic or hybrid spectroscopy

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Amplified molecular detection sensitivity in passive dielectric cavity

Cited by 3 publications

References 29 publications

CaF2: An Ideal Substrate Material for Infrared Spectroscopy?

CaF2: An Ideal Substrate Material for Infrared Spectroscopy?

Refractive Index Sensing of Monolayer Molecules Using Both Local and Propagating Surface Plasmons in Mid-Infrared Metagrating

Structures for surface-enhanced nonplasmonic or hybrid spectroscopy

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CaF₂: An Ideal Substrate Material for Infrared Spectroscopy?

CaF₂: An Ideal Substrate Material for Infrared Spectroscopy?