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 $4122\frac{\mathrm{nm}}{\mathrm{RIU}}$ can be expected, which translates to a figure of merit (FOM) of about 1421 ${\mathrm{RIU}}^{-1}$. 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.

Non-dispersive infrared (NDIR) absorption spectroscopy is a widespread approach to gas sensing due to its selectivity and conceptual simplicity. One of the main challenges towards the development of fully integrated NDIR sensors is the design and fabrication of microstructures, typically waveguides, that can combine high sensitivity with the ease of integrability of other sensor elements (sources, filters, detectors). Here, we investigate theoretically and experimentally a class of coupled strip-array (CSA) waveguides realized on a SiO₂/Si₃N₄ platform with mass semiconductor fabrication processes. We demonstrate that this class of waveguides shows comparable sensitivity for a wide range of presented geometries, making it a very promising platform for satisfying multiple sensor and fabrication requirements without loss of performance.

In this work, we present and analyze a design of an absorber–waveguide system combining a highly sensitive waveguide array concept with a resonant selective absorber. The waveguide part is composed of an array of coupled strip waveguides and is therefore called a coupled strip array (CSA). The CSA is then coupled to the end of a slab Tamm plasmon (STP-) resonator, which is composed of a quasicrystal-like reflector formed by the patterning of a silicon slab and an interfacing tungsten slab. The concept describes an emitter–waveguide or waveguide–detector system featuring selective plasmon-enhanced resonant absorption or emission. These are crucial properties for corresponding optical on-chip integrated devices in context with evanescent field absorption sensing in fluids or gases, for example. Thus, the concept comprises a valuable and more cost-effective alternative to quantum cascade lasers. We designed the lateral dimensions of the STP resonator via a simple quasi-crystal approach and achieved strong narrowband resonances (emittance and Q-factors up to 85% and 88, respectively) for different silicon thicknesses and substrate materials (air and silicon oxide). Moreover, we analyze and discuss the sensitivity of the complete emitter–waveguide system in dependence on the slab thickness. This reveals the crucial correlation between the expected sensitivity assigned to the absorber–waveguide system and field confinement within the silicon.

We demonstrate an experimental assessment of a high-Q, high-angle piezoelectric (2 µm PZT) MEMS scanning micromirror featuring distributed backside reinforcement, suitable for applications demanding energy-efficient and high-quality image projection. Frequency response measurements at 10 different vacuum levels ranging from atmospheric pressure to 10⁻⁶ mbar allow for the quantitative separation of damping mechanisms (air and structural). Stroboscopic digital holographic microscopy was used to assess the static and dynamic deformation of the mirror surface. The experimental results are in good agreement with simulations and models.

We demonstrate the design, fabrication and testing of a Fabry-Perrot filter array that can be adapted as an optical element in front of a sensor array. The technique uses nanoimprint lithography with a simple two-level master. The thickness of resin needed for each cavity is designed to match the resonant wavelength. Leveraging the local resin volume conservation, a modulation of the residual layer thickness is obtained by fill-factor engineering. The device is validated by transmission spectroscopy across the visible range.

Optical measurement approaches have proven to provide intrinsic selectivity and the sensitivity, required for the development of integrated gas sensors. In an ongoing project, we work towards a Si-photonics non-dispersive infrared gas sensor and are investigating the possibility of the incorporation of IR-plasmonic materials, which could allow an increase in sensitivities and reduce the size of such sensors. Here we present the basic concept and discuss in some detail first results concerning fabrication and characterization of the plasmonic properties.