Tuning of 2D rod-type photonic crystal cavity for optical modulation and impact sensing

We propose a novel way of mechanical perturbation of photonic crystal cavities for on-chip applications. We utilize the equivalence of the 2D photonic crystals with perfect electric conductor (PEC) boundary conditions to the infinite height 3D counterparts for rod type photonic crystals. Designed structures are sandwiched with PEC boundaries above and below and the perturbation of the cavity structures is demonstrated by changing the height of PEC boundary. Once a defect filled with air is introduced, the metallic boundary conditions is disturbed and the effective mode permittivity changes leading to a tuned optical properties of the structures. Devices utilizing this perturbation are designed for telecom wavelengths and PEC boundaries are replaced by gold plates during implementation. For 10 nm gold plate displacement, two different cavity structures showed a 21.5 nm and 26 nm shift in the resonant wavelength. Optical modulation with a 1.3 MHz maximum modulation frequency with a maximum power consumption of 36.81 nW and impact sensing with 20 μs response time (much faster compared to the commercially available ones) are shown to be possible

Electrically-Controlled Suppression of Rayleigh Backscattering in an Integrated Photonic Circuit

Undesirable light scattering is an important fundamental cause for photon loss in nanophotonics. Rayleigh backscattering can be particularly difficult to avoid in wave-guiding systems and arises from both material defects and geometric defects at the subwavelength scale. It has been previously shown that systems with broken time-reversal symmetry (TRS) can naturally suppress detrimental Rayleigh backscattering, but these approaches have never been demonstrated in integrated photonics or through practical TRS-breaking techniques. In this work, we show that it is possible to suppress disorder-induced Rayleigh backscattering in integrated photonics via electrical excitation, even when defects are clearly present. Our experiment is performed in a lithium niobate on insulator (LNOI) integrated ring resonator at telecom wavelength, in which TRS is strongly broken through an acousto-optic interaction that is induced via radiofrequency input. We present evidence that Rayleigh backscattering in the resonator is almost completely suppressed by measuring both the optical density of states and through direct measurements of the back-scattered light. We additionally provide an intuitive argument to show that, in an appropriate frame of reference, the suppression of backscattering can be readily understood as a form of topological protection

Breestraat 95 te Leiden, een statig huis uit de vijftiende eeuw

Contrary to what the eighteenth-century façade leads one to suspect, building- historical research has shown that the listed building Breestraat 95 is six centuries old. In this research the original shell with large cellar, two high floors and the authentic roof construction were documented. On the basis of wood samples the house proved to have been built between 1405 and 1411. What was special was that the original façade could be reconstructed on the basis of the building-historical research, a sixteenth-century print and bird’seye- view maps. It turns out that the house had a high screen façade. Due to the height of the house it is as if it had more floors, which was intended to impress. The presence of corner turrets reinforced this effect. The rare combination of building-historical data and old representations has led to a reliable reconstruction, so that we have now come to know more about this type of medieval architecture, which no longer exists in Leiden.Contrary to what the eighteenth-century façade leads one to suspect, building- historical research has shown that the listed building Breestraat 95 is six centuries old. In this research the original shell with large cellar, two high floors and the authentic roof construction were documented. On the basis of wood samples the house proved to have been built between 1405 and 1411. What was special was that the original façade could be reconstructed on the basis of the building-historical research, a sixteenth-century print and bird’seye- view maps. It turns out that the house had a high screen façade. Due to the height of the house it is as if it had more floors, which was intended to impress. The presence of corner turrets reinforced this effect. The rare combination of building-historical data and old representations has led to a reliable reconstruction, so that we have now come to know more about this type of medieval architecture, which no longer exists in Leiden

Het leemstucplafond van Rapenburg 65 te Leiden nader beschouwd

A recent restoration presented the opportunity for further research into the loam stucco ceiling of Rapenburg 65. In all probability this ceiling was realized by stucco worker Craeckenborch directly after 1623, when Matthias van Overbeke bought the building and had it almost completely rebuilt. The affinity this ceiling demonstrates with East-Netherlands and German ceilings is to be explained by the Cologne background of Van Overbeke.The ceiling appears to be an inextricable part of the construction of the building. The construction consists of pinewood joisting of secondary and tertiary beams and a roof construction with stacked trusses (with contemporary use of oak and lime wood).Between the tertiary beams small shelves have ingeniously been put in, to which the loam stucco was applied. The support of loam stucco is finished with a stucco layer on which a completely white geometric ceiling was created by means of profiled moulding and prefabricated ornaments

‘Een fraij gesicht’, het Leidse huis in de 17de eeuw. Een poging tot typologisering

From recent systematic building-historical research in the town of Leiden a frequently applied type of house emerged. This type of house appears to have been applied in the 17th century, but seems to have been introduced in the period of peace and prosperity after the relief of Leiden in 1574. The type has a characteristic design and plan.The plan consists of a deep front part of the house with a separate rear part of the house or a rear extension. The plan has a specific layout and particularly on the ground floor a logical use of space is to be seen, related to daylight access. The major rooms face the external wails with the bedrooms and vertical transport in between.The functions on the ground floor are a shop/workshop facing the street with a heated dayroom with box bed belonging to the shop/workshop. The rear extension or the separate rear part of the house has a kitchen function. The layout of the floor (if existing) contains two heated living rooms, also with box beds in the middle zone.The ground floor probably functioned as a business zone and the floor as a living zone, when the business was closed. As the houses lack a large storage capacity, trades were practiced, for instance related to the textile industry, for which such capacity was not required. The structural principles are brick walls, with joint walls as side elevations.The floors show the transition from the generally older floor construction with composite wooden joisting to the more modern floor with simple joisting. Both principles occur, in the first as well as in the later town extensions (1611 and 1644/1658). A composite joisting was preferred, at any rate for the representative rooms.For the construction of the roof trusses with triangle trusses on top of them were usually applied. The wooden vice in a brick stairwell is part of the construction. This type of house was frequently built from the end of the 16th century, having its peak in the 17th-century town extensions. It was such a practical type that in the 19th century new versions were still built

Fecal shedding and tissue infections demonstrate transmission of Mycobacterium avium subsp. paratuberculosis in group-housed dairy calves

International audienceAbstractCurrent Johne’s disease control programs primarily focus on decreasing transmission of Mycobacterium avium subsp. paratuberculosis (MAP) from infectious adult cows to susceptible calves. However, potential transmission between calves is largely overlooked. The objective was to determine the extent of MAP infection in calves contact-exposed to infectious penmates. Thirty-two newborn Holstein–Friesian calves were grouped into 7 experimental groups of 4, consisting of 2 inoculated (IN) calves, and 2 contact-exposed (CE) calves, and 1 control pen with 4 non-exposed calves. Calves were group housed for 3 months, with fecal samples were collected 3 times per week, blood and environmental samples weekly, and tissue samples at the end of the trial. The IN calves exited the trial after 3 months of group housing, whereas CE calves were individually housed for an additional 3 months before euthanasia. Control calves were group-housed for the entire trial. All CE and IN calves had MAP-positive fecal samples during the period of group housing; however, fecal shedding had ceased at time of individual housing. All IN calves had MAP-positive tissue samples at necropsy, and 7 (50%) of the CE had positive tissue samples. None of the calves had a humoral immune response, whereas INF-γ responses were detected in all IN calves and 5 (36%) CE calves. In conclusion, new MAP infections occurred due to exposure of infectious penmates to contact calves. Therefore, calf-to-calf transmission is a potential route of uncontrolled transmission on cattle farms

Jacob Roman, een innovatieve ontwerper?

We know less about the architect Jacob Roman (1640-1716) than his reputation would suggest. From 1681 he was Leiden’s city architect and subsequently, from 1689 to 1702, architect to Stadholder-King William III. Partly as a result of these official posts, it is difficult to form an accurate picture of his output. In his commissions for close friends of Willem III he collaborated with Daniël Marot and Steven Vennecool. He moved in the highest social circles, was well informed about recent architectural developments and had access to the Bibliotheca Thysiana in Leiden, which housed all relevant contemporary architectural treatises. He was able to consult these works even before 1689, when he followed Willem III to England, where he studied the work of Inigo Jones and Christopher Wren at first hand. After his return to the Netherlands, his architecture took on a more austere classical form. This is evident from the new facade for the town hall of Deventer from 1694, the specifications for which are referenced for the first time in this article. Roman is also important because of his role in the design of fountains and the introduction in the Netherlands of sliding windows and a new kind of roof construction in which an all-round hipped roof was combined with the possibility of realizing a large formal space below it. He had already employed this in 1681 for Hofje Meermansburg in Leiden, and in 1694 he used it again for the town hall in Deventer. It involves the use of a kings post in the roof construction, whereby a braced middle post eliminates the need for a central support in the room below. It turns out that rather than discovering this Italian-inspired solution during his time in England, where such roof constructions were then being used, Roman had already read about it back in Leiden, courtesy of the treatises available in Bibliotheca Thysiana. &nbsp

Plasma oxidation as key mechanism for stoichiometry in Pulsed Laser Deposition grown oxide films

We present a unique overview on the influence of growth parameters on the characteristics of the PLD plasma plume using Optical Self-Emission (OSE) imaging and spectroscopy, supported with Laser Induced Fluorescence (LIF) measurements. It is shown that in a relatively small background gas pressure regime, from 10-2 mbar to 10-1 mbar oxygen pressure, a transition from nonstoichiometric to stoichiometric growth of SrTiO3 films occurs as measured with X-ray Diffraction (XRD). In this pressure regime, OSE spectroscopy and LIF measurements also show a transition from incomplete to full oxidation of species in the plasma plume. This suggests that the oxidation of species in the plasma is a crucial mechanism for the stoichiometric reconstruction of the synthesized oxide thin films