Generation of broadband near-field optical spots using a thin-film silicon waveguide with gradually changing thickness

Zhang, Kaifeng; Taniguchi, Shin‐ichi; Tachizaki, Takehiro

doi:10.1364/ol.43.005937

Cited by 8 publications

(11 citation statements)

References 28 publications

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“…Our previous study confirmed that the excitation beam had a focusing angle of ∼2° Figure c shows the calculated reflectance of the three-layer Si/Au/vacuum system.…”

Section: Methodssupporting

confidence: 77%

“…This is the optimal thickness obtained by numerically solving the Fresnel equation for a three-layered (Si/Au/vacuum) junction, with a 660 nm excitation laser wavelength (Figures S1, S2 in the Supporting Information). , As indicated by the dotted line in Figure a, an FIB-assisted process, which can be executed programmatically by using the designed information of the probe, was employed to remove a portion of the pyramid from the tip.…”

Section: Methodsmentioning

confidence: 99%

“…This thin-film Si geometry significantly reduces the absorption of the excitation energy by the excessively thick Si layers. The FIB cutting angle was accurately designed so that a wedge-type Si layer was formed, with the upper surface and lower surface forming an angle α of ∼2°(See inset in Figure b) . As the refractive index of Si is relatively high (3.85), this ensures that the excitation laser can penetrate the air/Si interface at an incident angle θ air–Si of 61.3° only if the angle α is above 1.2°.…”

Section: Methodsmentioning

confidence: 99%

“…Our previous study confirmed that the excitation beam had a focusing angle of ∼2°. 34 Figure 1c shows the calculated reflectance of the three-layer Si/Au/vacuum system. The solid line indicates reflectance at different focusing angles by analytical calculation.…”

mentioning

confidence: 99%

“…The FIB cutting angle was accurately designed so that a wedge-type Si layer was formed, with the upper surface and lower surface forming an angle α of ∼2°(See inset in Figure 1b). 34 As the refractive index of Si is relatively high (3.85), this ensures that the excitation laser can penetrate the air/Si interface at an incident angle θ air−Si of 61.3°only if the angle α is above 1.2°. In this configuration, the laser can be refracted to the Au layer at θ Si−Au = 15.9°, that is, the SPR incident angle (Figure 1c).…”

mentioning

confidence: 99%

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Low-Background Tip-Enhanced Raman Spectroscopy Enabled by a Plasmon Thin-Film Waveguide Probe

et al. 2021

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Tip-enhanced Raman spectroscopy (TERS) is a nano-optical approach to extract spatially resolved chemical information with nanometer precision. However, in the case of direct-illumination TERS, which is often employed in commercial TERS instruments, strong fluorescence or far-field Raman signals from the illuminated areas may be excited as a background. They may overwhelm the near-field TERS signal and dramatically decrease the near-field to far-field signal contrast of TERS spectra. It is still challenging for TERS to study the surface of fluorescent materials or a bulk sample that cannot be placed on an Au/Ag substrate. In this study, we developed an indirect-illumination TERS probe that allows a laser to be focused on a flat interface of a thin-film waveguide located far away from the region generating the TERS signal. Surface plasmon polaritons are generated stably on the waveguide and eventually accumulated at the tip apex, thereby producing a spatially and energetically confined hotspot to ensure stable and high-resolution TERS measurements with a low background. With this thin-film waveguide probe, TERS spectra with obvious contrast from a diamond plate can be acquired. Furthermore, the TERS technique based on this probe exhibits excellent TERS signal stability, a long lifetime, and good spatial resolution. This technique is expected to have commercial potential and enable further popularization and development of TERS technology as a powerful analytical method.

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“…Our previous study confirmed that the excitation beam had a focusing angle of ∼2° Figure c shows the calculated reflectance of the three-layer Si/Au/vacuum system.…”

Section: Methodssupporting

confidence: 77%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Low-Background Tip-Enhanced Raman Spectroscopy Enabled by a Plasmon Thin-Film Waveguide Probe

et al. 2021

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Simple cleaning and regeneration of tip‐enhanced Raman spectroscopy probe with UV sources

Zhang

Taniguchi

Saeki

et al. 2022

J Raman Spectroscopy

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Tip‐enhanced Raman spectroscopy (TERS) is a powerful nano‐optical approach that allows the extraction of nanometer resolved chemical information. The key to a successful TERS measurement is the quality of the TERS tip. However, tip contamination, which usually occurs during measurements on samples that include organic molecules or after long‐term storage, remains a critical problem for TERS experiments. It not only affects the reliability of TERS results but also hinders the long‐term development of the TERS technique. Herein, we propose a method that enables the regeneration of contaminated TERS tips. For this purpose, we prepared a TERS tip contaminated by stable organic molecules, which was subjected to a simple and rapid ultraviolet (UV) cleaning procedure to remove the contaminants and to regenerate the tip. This method is demonstrated to be effective in removing the contaminants from the TERS tip by directly breaking the bonds in the contaminated molecules and oxidizing organic compounds with the generated reactive oxygen atom. This simple method could propel the development of the TERS technique.

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A dual-use probe for nano-metric photoelectric characterization using a confined light field generated by photonic crystals in the cantilever

Hou

Wang

et al. 2021

Nano Res.

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Generation of broadband near-field optical spots using a thin-film silicon waveguide with gradually changing thickness

Cited by 8 publications

References 28 publications

Low-Background Tip-Enhanced Raman Spectroscopy Enabled by a Plasmon Thin-Film Waveguide Probe

Low-Background Tip-Enhanced Raman Spectroscopy Enabled by a Plasmon Thin-Film Waveguide Probe

Simple cleaning and regeneration of tip‐enhanced Raman spectroscopy probe with UV sources

A dual-use probe for nano-metric photoelectric characterization using a confined light field generated by photonic crystals in the cantilever

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