Calculations of electromagnetic fields in longitudinal irregular TEM-cells

TEM-cells can be used as a standardized field generator for field probe calibration purposes or electromagnetic compatibility measurements. Because of its practical use as a measurement environment, the electromagnetic behavior over a broad range of frequencies is essential. However, without the understanding of wave reflection, mode-conversion, and attenuation, using such a measurement environment is impractical. In this contribution, we calculate the electromagnetic fields in a longitudinal irregular coaxial TEM-cell. Using a semi-analytical approach, we can determine these wave characteristics. The method is based on the projection of Maxwell's equations onto eigenfunctions. This work's primary objective is to examine the effect of irregular deformed boundaries on the electromagnetic field and the resonance frequencies.

Soft X-ray Lensless Imaging in Reflection Mode

We report on the development and implementation of methodologies dedicated to soft X-ray imaging by coherent scattering in reflection mode. Two complementary approaches are tested, based on Fourier transform holography and on ptychography. A new method for designing holographic masks has been developed. Our results represent a feasibility test and highlight the potential and limitations of imaging in reflection mode. Reflectivity is less efficient than transmission at soft X-ray wavelengths, hampering the acquisition of good quality images. Nonetheless, it has the potential to image a wider set of samples, notably those that are not transparent to soft X-rays. Although the images obtained so far are of modest quality, these results are extremely encouraging for continuing the development of coherent soft X-ray imaging in reflection mode.

Application of acoustic microscopy for evaluation of numismatic material

A new non-destructive express method for assessing the authenticity of numismatic material is considered in the paper. Non-destructive methods of pulsed acoustic microscopy in the frequency range of 50-100 MHz were applied. Samples of silver coins dated 1924 and 1979 were examined. The characteristic values of the longitudinal and transverse sonic velocity of the samples were obtained. The method of hydrostatic weighing was used to measure the density of the metal. It was shown that assessment of the authenticity and the safety degree of coins can also be carried out by revealing the internal defects such as corrosion. Acoustic visualization in the reflection mode allows imaging the offset of the obverse relative to the reverse and to determine the centre of the coin deviation, which also confirms the quality of the minting.

Submicron Non-contact Simultaneous Infrared and Raman Spectroscopy for Challenging Failure Analysis

We introduce a new infrared (IR) technique that provides submicron spatial resolution by making use of an infraredvisible, pump-probe arrangement that also offers a simultaneous Raman measurement in formerly challenging failure and contamination analyses. These challenges are typically due to the lack of spatial resolution and sample preparation restrictions from conventional FTIR, plus auto-fluorescence (AF) from Raman spectroscopy. Such a combined Optical PhotoThermal InfraRed (O-PTIR) and Raman instrumentation offers spatial resolution improvement over conventional IR measurements by 30 times at 1000 cm-1. The technique also improves sensitivity to exceptionally small quantities (? 400 femtogram) in reflection mode by sensing the photothermal response arising from absorbing infrared radiation (Fig. 1) [1]. The AF-free O-PTIR technique also delivers constant spatial resolution over the entire mid-IR range due to the use of a fixed wavelength probe beam at 532 nm [2]. Simultaneous Raman confirms and complements the O-PTIR measurements in cases with low AF. We will illustrate three examples that will highlight the advantage of the novel technique commonly observed in the failure and contamination analysis community.

Multifunctional Gratings for Multiband Spatial Filtering, Retroreflection, Splitting and Demultiplexing Based on C2 Symmetric Photonic Crystals

The concept of multifunctional reflection-mode gratings based on rod-type photonic crystals with C2 symmetry is introduced and examined. The specific modal properties lead to the vanishing dependence of the first-negative-order maximum on the angle of incidence within a wide range, and the nearly sinusoidal redistribution of the incident-wave energy between zero order (specular reflection) and first negative diffraction order (deflection) at frequency variation that are the key features enabling various functionalities in one structure and functionality merging. The elementary functionalities offered by the studied structures, of which multifunctional scenarios can be designed, include but are not restricted to multiband spatial filtering, multiband splitting, and demultiplexing. The proposed structures are shown to be capable in multifunctional operation in case of an obliquely incident polychromatic wave. The generalized demultiplexing is demonstrated for the case when several polychromatic wavesare incident at different angles. The same deflection properties yield multiband splitting, and merging demultiplexing and splitting functionalties in one functionality, which may contribute to various multifunctional scenarios. The proposed gratings arealso studied in transmissive configuration.

Reflection-Mode Ultrasound Computed Tomography Based on Wavelet Processing for High-Contrast Anatomical and Morphometric Imaging

Medical B-mode ultrasound is widely used for the examination of children’s limbs, including soft tissue, muscle, and bone. However, for the accurate examination of the bone only, it is often replaced by more restrictive clinical modalities. Several authors have investigated ultrasonic imaging of bone to assess cortical thickness and/or to estimate the wave velocity through the internal structure. The present work focuses on the transverse slice imaging process using reflection-mode ultrasound computed tomography (USCT). The method is valid for imaging soft tissues with similar acoustic impedances, but in the presence of bone, the higher contrasts alter the propagation of ultrasonic waves and reduce the contrast-to-noise ratio (CNR). There is a need to change the methods used for the processing of ultrasonic signals. Our group has developed a wavelet-based coded excitation (WCE) method to process information in frequency and time. The objective of this study is to use the method to improve reflection-mode USCT, at low ultrasonic intensities, to better address organ morphometry. Experimental results on a newborn arm phantom and on an ex vivo chicken drumstick are presented, and the usefulness of this WCE-mode USCT is discussed.