In this this paper we quickly derive the Kramers-Kronig relations from simple causality considerations and propose a simple way to implement them using the Fast Fourier Transform. This work focuses on how to make these relations a usable tool even when their conditions of validity are not strictly respected. In this respect we emphasize on their application to the constant low level loss approximation at microwave frequencies. The method presented is demonstrated on various typical cases of fancy propagation: high velocity, negative phase velocity and evanescent waves.

The implementation of space charge measurements based on thermal perturbation on thin films requires an improvement of the temperature distribution estimation at the surface and in the depth of dielectric materials for getting reliable space charge profile measurements. Absolute temperature variations are needed, both in time and space. The present contribution addresses surface temperature measurements based on either thermoelectric or bolometric effects. Both responses have been measured on copper-coated silicon nitride layers and gold-coated polypropylene films heated with a Nd:YAG laser pulse. It is shown that high temporal resolution thermal response can be obtained through the bolometric response and that the information appears nearly independent on the nature of the coating electrode. The setup developed provides good signal to noise ratio for heated electrodes of a few ohm resistance. Strategies are still to develop to get the temperature profile in the insulating sample layer.

We present a microwave photoconductive switch based on exfoliated black phosphorus and strongly responding to a 1.55 μm optical excitation. According to its number of atomic layers, exfoliated black phosphorus presents unique properties for optoelectronic applications, like a tunable direct bandgap from 0.3 eV to 2 eV, strong mobilities, and strong conductivities. The switch shows a maximum ON/OFF ratio of 17 dB at 1 GHz, and 2.2 dB at 20 GHz under 1.55-μm laser excitation at 50 mW, never achieved with bidimensional materials.

This paper presents a sensor which can be included in an Advanced Driver Assistance System (ADAS) that is compliant with the Vehicle to Infrastructure communication standard (V2I). This system allows estimation of the vehicle lateral position in real time by ensuring cooperation between an on-board vehicle system and passive transponders integrated in the lateral white strips of the road. Based on an optimization method, the lateral position vehicle is provided with a distance error less than 3 cm. In this paper, experimental results are presented in order to evaluate the robustness of the proposed system in a realistic environment. Three scenarios are considered to take into account the bitumen properties, the presence of parasitic reflectors in different positions around the system and the interaction between transponders.

In this article, angle and polarization-resolved absorption and time-resolved pump-probe measurements have been carried out on multilayer black phosphorus (BP) at infrared wavelength (around 1550 nm), which is an extension of the previous studies of the BP behavior done at higher frequency [Lazar et al., Nanoscale 10(19), 8979–8988 (2018)]. Exfoliated down to a few layers, BP reveals the properties of a 2D material with anisotropic response, high mobility (up to 10 000 cm²/V/s), and absorption, which are very relevant to optoelectronics. BP bandgap is tunable according to the number of layers, allowing applications from UV to IR. The bandgap height of the single and thicker layers has been measured through absorption and reflection spectra. We report the measurement of the ambipolar carrier lifetime, which has been determined to be about 15 ps. The structure-induced anisotropy is studied. The results confirm BP as a suitable material for ultrafast devices such as microwave photoswitches, samplers, terahertz antenna, for instance.