Aluminium, gold-tin and titanium-tungsten alloys for mid-infrared plasmonic gratings

Spettel, Jasmin; Stocker, Gerald; Dao, Thang Duy; Jannesari, Reyhaneh; Tortschanoff, A.; Saeidi, Parviz; Pühringer, Gerald; Dubois, Florian; Fleury, Clément; Consani, Cristina; Grille, Thomas; Aschauer, E.; Moridi, Mohssen; Jakoby, Bernhard

doi:10.1364/ome.417877

Cited by 9 publications

(6 citation statements)

References 31 publications

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“…For wavelengths beyond 4.25 µm, the absorption of CO 2 present in the ambient air is perceptible in the data. The presented data are connected to the preliminary first experimental results published in [26].…”

Section: Resultssupporting

confidence: 55%

Ultra-Narrow SPP Generation from Ag Grating

Stocker

Spettel

Dao

et al. 2021

Sensors

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In this study, we investigate the potential of one-dimensional plasmonic grating structures to serve as a platform for, e.g., sensitive refractive index sensing. This is achieved by comparing numerical simulations to experimental results with respect to the excitation of surface plasmon polaritons (SPPs) in the mid-infrared region. The samples, silver-coated poly-silicon gratings, cover different grating depths in the range of 50 nm–375 nm. This variation of the depth, at a fixed grating geometry, allows the active tuning of the bandwidth of the SPP resonance according to the requirements of particular applications. The experimental setup employs a tunable quantum cascade laser (QCL) and allows the retrieval of angle-resolved experimental wavelength spectra to characterize the wavelength and angle dependence of the SPP resonance of the specular reflectance. The experimental results are in good agreement with the simulations. As a tendency, shallower gratings reveal narrower SPP resonances in reflection. In particular, we report on 2.9 nm full width at half maximum (FWHM) at a wavelength of 4.12 µm and a signal attenuation of 21%. According to a numerical investigation with respect to a change of the refractive index of the dielectric above the grating structure, a spectral shift of 4122nmRIU can be expected, which translates to a figure of merit (FOM) of about 1421 RIU−1. The fabrication of the suggested structures is performed on eight-inch silicon substrates, entirely accomplished within an industrial fabrication environment using standard microfabrication processes. This in turn represents a decisive step towards plasmonic sensor technologies suitable for semiconductor mass-production.

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Section: Resultssupporting

confidence: 55%

Ultra-Narrow SPP Generation from Ag Grating

Stocker

Spettel

Dao

et al. 2021

Sensors

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“…The propagation length is the distance after which the intensity of a propagating SPP mode is reduced by 1/e. Since the intensity is proportional to the squared field quantities, the propagation length can be calculated by [38,40]:…”

Section: Propagation Lengthmentioning

confidence: 99%

Designing Mid-Infrared Gold-Based Plasmonic Slot Waveguides for CO2-Sensing Applications

Saeidi

Jakoby

Pühringer

et al. 2021

Sensors

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Plasmonic slot waveguides have attracted much attention due to the possibility of high light confinement, although they suffer from relatively high propagation loss originating from the presence of a metal. Although the tightly confined light in a small gap leads to a high confinement factor, which is crucial for sensing applications, the use of plasmonic guiding at the same time results in a low propagation length. Therefore, the consideration of a trade-off between the confinement factor and the propagation length is essential to optimize the waveguide geometries. Using silicon nitride as a platform as one of the most common material systems, we have investigated free-standing and asymmetric gold-based plasmonic slot waveguides designed for sensing applications. A new figure of merit (FOM) is introduced to optimize the waveguide geometries for a wavelength of 4.26 µm corresponding to the absorption peak of CO2, aiming at the enhancement of the confinement factor and propagation length simultaneously. For the free-standing structure, the achieved FOM is 274.6 corresponding to approximately 42% and 868 µm for confinement factor and propagation length, respectively. The FOM for the asymmetric structure shows a value of 70.1 which corresponds to 36% and 264 µm for confinement factor and propagation length, respectively.

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“…33−37 Within the context of open cavities, arrays of monopole antennas on conductive substrates have been shown to possess high-quality resonances (Q ∼ 200), 38,39 whereas the quality of continuous stripe gratings resonant in the midinfrared spectral region was significantly lower. 33,40 Half-wavelength infrared antennas are known as highly efficient substrates for surface-enhanced vibrational spectroscopy, 41−44 including ultrafast and multidimensional spectroscopic methods in the mid-infrared spectral region. 45−50 The resonant wavelength of infrared antennas can be easily tuned by adjusting their length.…”

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confidence: 99%

Infrared Open Cavities for Strong Vibrational Coupling

Cohn

Das

Basu

et al. 2021

J. Phys. Chem. Lett.

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Arrays of subwavelength plasmonic nanoparticles exhibiting narrowband lattice resonances are referred to as open cavities because of their ability to strongly couple with electronic excitations in molecular chromophores. However, realization of these ideas in the mid-infrared spectral region has been limited. We demonstrated a dramatic reduction in the bandwidth of lattice resonances in large-area arrays of half-wavelength mid-infrared antennas, reaching resonance quality factors above 200. By tuning the wavelength of the antenna-lattice resonances (ALR) to match the transition frequency of the molecular vibrational modes, we achieved a strong coupling between the ALR and the carbonyl stretching excitation in a thin film of (poly)methyl methacrylate (PMMA) polymer deposited on the array. Splitting of the polaritonic transitions, reduction of their bandwidth below that of the bare molecular transition, and characteristic dispersion confirmed the strong coupling regime. Our results pave the way for exciting research on the many-body correlated dynamics of vibrational polaritons.

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Aluminium, gold-tin and titanium-tungsten alloys for mid-infrared plasmonic gratings

Cited by 9 publications

References 31 publications

Ultra-Narrow SPP Generation from Ag Grating

Ultra-Narrow SPP Generation from Ag Grating

Designing Mid-Infrared Gold-Based Plasmonic Slot Waveguides for CO2-Sensing Applications

Infrared Open Cavities for Strong Vibrational Coupling

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