Cyclododecane as a contrast improving substance for the terahertz imaging of artworks

This paper presents measurements of the terahertz properties of the art conservation substance cyclododecane, demonstrating that it can act as a contrast improving agent in the terahertz imaging of concealed wall paintings. Results are presented which show that the terahertz optical properties of cyclododecane are dependent on the rate at which it has cooled from the melt. Based on the results, a theoretical explanation of the contrast enhancement mechanism is postulated. The findings presented here may lead to the development of novel coating materials that could improve the quality of terahertz images in a variety of fields and not just in art conservation

Reliable 50Gb/s silicon photonics platform for next-generation data center optical interconnects

The next generations of data centers require a scalable optical transceiver technology. In this paper we present a silicon photonics platform supporting single-channel data rates of 50Gb/s and above. Advanced process options include 50GHz GeSi electro-absorption modulators, high efficiency thermo-optic phase shifters with P-pi <5mW and silicon carrier depletion-based phase-shifters supporting Mach-Zehnder and micro-ring modulators. The performance and reliability of the key library components such as modulators, detectors, fiber couplers and heaters is described

Round robin tests on laser ablation and quantitative analysis by LIBS

Referring to the “Seven ages of an analytical method” proposed by Laitinen in 19731, LIBS may be presently considered at the threshold of the sixth one, when the number of applications of the technique has significantly increased, and the need of standardization is simultaneously growing. While the preferred scope of LIBS applications is onsite, online or in situ analysis, the diversity of experimental configurations required to address such issues is somewhat contradictory with a standardization approach. An alternative way to make LIBS progress to become a fully mature analytical technique could be the determination of reference performances of different instruments or experimental setups for a given analytical case. Such an approach would have several advantages: 1) Newcomers, both researchers and industrials, could better evaluate if the technique could meet their needs; 2) It would be a solid basis to which enhancement approaches could be compared (e.g. hyphenated techniques, microwave assisted LIBS, etc.); 3) It could help to define good experimental configurations and analytical practices that could be of general interest for any application. For that purpose, two round robin tests have been organized since 2012 within the French LIBS community. The first one involved five laboratories and was focused on the characterization of laser ablation of iron. Very consistent results on the craters volume were obtained, but no correlation was found between the repeatability of laser ablation and that of the LIBS signal. The second one was devoted to quantitative analysis of glass samples. Eleven teams contributed to the work. In spite of the dispersion in the experimental setups and protocols, the results obtained on unknowns showed an acceptable bias, whereas the measurement uncertainty was much more variable among the participants. Overall, the results of those two preliminary round robin tests show that a good reproducibility level is reachable between independent LIBS measurements and, in this sense, are very encouraging for the future