International audienceThis paper describes the realization and characterization of microwave 3-D printed loads in rectangular waveguide technology. Several commercial materials were characterized at X-band (8-12 GHz). Their dielectric properties were extracted through the use of a cavity-perturbation method and a transmission/reflection rectangular waveguide method. A lossy carbon-loaded Acrylonitrile Butadiene Styrene (ABS) polymer was selected to realize a matched load between 8 and 12 GHz. Two different types of terminations were realized by fused deposition modeling: a hybrid 3-D printed termination (metallic waveguide + pyramidal polymer absorber + metallic short circuit) and a full 3-D printed termination (self-consistent matched load). Voltage standing wave ratio of less than 1.075 and 1.025 were measured over X-band for the hybrid and full 3-D printed terminations, respectively. Power behavior of the full 3-D printed termination was investigated. A very linear evolution of reflected power as a function of incident power amplitude was observed at 10 GHz up to 11.5 W. These 3-D printed devices appear as a very low cost solution for the realization of microwave matched loads in rectangular waveguide technology
Subpicosecond optical transmission experiments are used to compare saturable absorber ͑SA͒ based on bundled single-walled carbon nanotubes ͑SWNT͒ and iron-doped InGaAs/InP epitaxial multiple quantum wells ͑MQW͒ at 1.55 m telecom wavelength. The SA key parameters ͑contrast ratio, saturation fluence, and recovery time͒ relevant for high speed all optical signal regeneration ͑AOSR͒ are extracted from the normalized differential transmission ͑NDT͒. Although both SA exhibit good contrast ratios, SWNT show a full signal recovery as well as a much faster response time than MQW. This original work on SA shows that SWNT are excellent candidates for future low cost AOSR.
This paper demonstrates the realization of submicrometric patterns by using standard photolithography (365 nm). Significant improvements in standard photolithography resolution can be achieved with specific conditions of a very thin layer of photoresist (0.13 µm). Usually, standard photolithography has a resolution limit of about 1 µm. Firstly, using Kirchhoff diffraction theory we show that with these new conditions the theoretical resolution limit could be 0.4 µm. Secondly, in the experimental part, the realization of 0.8 µm size patterns is demonstrated.
With the multiplication of electronic devices in our daily life, there is a need for tailored wideband electromagnetic (EM) absorbers that could be conformed on any type of surface-like antennas for interference attenuation or military vehicles for stealth applications. In this study, a wideband flexible flat electromagnetic absorber compatible with additive manufacturing has been studied in the X-Ku frequency bands. A multilayer structure has been optimized using a genetic algorithm (GA), adapting the restrictions of additive manufacturing and exploiting the EM properties of loaded and non-loaded filaments, of which the elaboration is described. After optimization, a bi-material multilayer absorber with a thickness of 4.1 mm has been designed to provide a reflectivity below −12 dB between 8 and 18 GHz. Finally, the designed multilayer structure was 3D-printed and measured in an anechoic chamber, achieving −11.8 dB between 7 and 18 GHz. Thus, the development of dedicated materials has demonstrated the strong potential of additive technologies for the manufacturing of thin wideband flexible EM absorbers.
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