The problem of electromechanical film characterization, and, in particular, the determination of the piezoelectric activities of thin films deposited on substrates, is of fundamental importance in the development of structures for microelectromechanical system (MEMS) applications. The design and the architecture of the piezoelectric MEMS are directly related to the mechanical and the piezoelectric performances of the material. In this article, we present and compare some results obtained on different experimental setup for the determination of the d33 coefficient. We have optimized the experimental conditions using a laser Doppler vibrometer. The main problem is the contribution of the bending effect of the substrates on the d33 coefficient, which is an intrinsic property of the film. We show that the d33 values are directly related to parameters such as the top electrode diameter and the substrate holder. The results are in agreement with those obtained with the conventional double beam interferometer used to account for substrate bending.

Severe acute respiratory syndrome SARS-CoV-2 virus led to notable challenges amongst researchers in view of development of new and fast detecting techniques. In this regard, surface-enhanced Raman spectroscopy (SERS) technique, providing a fingerprint characteristic for each material, would be an interesting approach. The current study encompasses the fabrication of a SERS sensor to study the SARS-CoV-2 S1 (RBD) spike protein of the SARS-CoV-2 virus family. The SERS sensor consists of a silicon nanowires (SiNWs) substrate decorated with plasmonic silver nanoparticles (AgNPs). Both SiNWs fabrication and AgNPs decoration were achieved by a relatively simple wet chemical processing method. The study deliberately projects the factors that influence the growth of silicon nanowires, uniform decoration of AgNPs onto the SiNWs matrix along with detection of Rhodamine-6G (R6G) to optimize the best conditions for enhanced sensing of the spike protein. Increasing the time period of etching process resulted in enhanced SiNWs’ length from 0.55 to 7.34 µm. Furthermore, the variation of the immersion time in the decoration process of AgNPs onto SiNWs ensued the optimum time period for the enhancement in the sensitivity of detection. Tremendous increase in sensitivity of R6G detection was perceived on SiNWs etched for 2 min (length=0.90 µm), followed by 30s of immersion time for their optimal decoration by AgNPs. These SiNWs/AgNPs SERS-based sensors were able to detect the spike protein at a concentration down to 9.3 × 10 −12 M. Strong and dominant peaks at 1280, 1404, 1495, 1541 and 1609 cm −1 were spotted at a fraction of a minute. Moreover, direct, ultra-fast, facile, and affordable optoelectronic SiNWs/AgNPs sensors tuned to function as a biosensor for detecting the spike protein even at a trace level (pico molar concentration). The current findings hold great promise for the utilization of SERS as an innovative approach in the diagnosis domain of infections at very early stages.

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International audienceThe waveguideproperties are reported for wide bandgap gallium nitride(GaN) structures grown by metal organic vapor phase epitaxy on sapphire using a AlN/GaN short period-superlattice (SPS) buffer layer system. A detailed optical characterization of GaN structures has been performed using the prism coupling technique in order to evaluate its properties and, in particular, the refractive index dispersion and the propagation loss. In order to identify the structural defects in the samples, we performed transmission electron microscopy analysis. The results suggest that AlN/GaN SPS plays a role in acting as a barrier to the propagation of threading dislocations in the active GaN epilayer; above this defective region, the dislocations density is remarkably reduced. The waveguide losses were reduced to a value around 0.65dB/cm at 1.55μm, corresponding to the best value reported so far for a GaN-based waveguide

Lithium niobate's use in integrated optics is somewhat hampered by the lack of a capability to create low loss waveguides with strong lateral index confinement. Thin film single crystal lithium niobate is a promising platform for future applications in integrated optics due to the availability of a strong electro-optic effect in this material coupled with the possibility of strong vertical index confinement. However, sidewalls of etched waveguides are typically rough in most etching procedures, exacerbating propagation losses. In this paper, we propose a fabrication method that creates significantly smoother ridge waveguides. This involves argon ion milling and subsequent gas clustered ion beam smoothening. We have fabricated and characterized ultra-low loss waveguides with this technique, with propagation losses as low as 0.3 dB/cm at 1.55 µm.

Electro‐optic modulators are among the most important building blocks in optical communication networks. Lithium niobate, for example, has traditionally been widely used to fabricate high‐speed optical modulators due to its large Pockels effect. Another material, barium titanate, nominally has a 50 times stronger r‐parameter and would ordinarily be a more attractive material choice for such modulators or other applications. In practice, barium titanate thin films for optical waveguide devices are usually grown on magnesium oxide due to its low refractive index, allowing vertical mode confinement. However, the crystal quality is normally degraded. Here, a group of scandate‐based substrates with small lattice mismatch and low refractive index compared to that of barium titanate is identified, thus concurrently satisfying high crystal quality and vertical optical mode confinement. This work provides a platform for nonlinear on‐chip optoelectronics and can be promising for waveguide‐based optical devices such as Mach–Zehnder modulators, wavelength division multiplexing, and quantum optics‐on‐chip.

Enhanced thermoelectric performance of c-axis oriented Bi1−xPbxCuSeO single crystalline thin films.

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