Multiplication and division of the orbital angular momentum of light with diffractive transformation optics

We present a method to efficiently multiply or divide the orbital angular momentum (OAM) of light beams using a sequence of two optical elements. The key-element is represented by an optical transformation mapping the azimuthal phase gradient of the input OAM beam onto a circular sector. By combining multiple circular-sector transformations into a single optical element, it is possible to perform the multiplication of the value of the input OAM state by splitting and mapping the phase onto complementary circular sectors. Conversely, by combining multiple inverse transformations, the division of the initial OAM value is achievable, by mapping distinct complementary circular sectors of the input beam into an equal number of circular phase gradients. The optical elements have been fabricated in the form of phase-only diffractive optics with high-resolution electron-beam lithography. Optical tests confirm the capability of the multiplier optics to perform integer multiplication of the input OAM, while the designed dividers are demonstrated to correctly split up the input beam into a complementary set of OAM beams. These elements can find applications for the multiplicative generation of higher-order OAM modes, optical information processing based on OAM-beams transmission, and optical routing/switching in telecom.Comment: 28 pages, 10 figure

Le molte vite di Adolfo Rossi: emigrante, giornalista, ispettore, diplomatico

Adolfo Rossi (1857-1921) was a figure of relevance in the Italy of the XIX century. Native of the province of Rovigo, in the region of Veneto, aself-taught person, he was first a poor emigrant to the USA who became a journalist and combatant at the end of the century, hired by the most important newspapers; then, he was an itinerant inspector at the Commissariato Generale dell'Emigrazione (1902) and, finally, he was a diplomat in the Americas (from 1908) charged with duties in the Ministero italiano degli Esteri. He was the author of memorable journalistic reportages about social events and about the misery of the life in the peninsular campaign. Meanwhile, his harsh missives from Eritrea led to his expulsion from the colony a few days before the disastrous defeat of Adwa (1896). The texts he wrote about the state of the Italian emigration in Brazil, South Africa, the USA and Argentina 'precise, dramatic, almost photographic, absolutely real texts' caused a sensation and contributed to change the migration policy of the authorities of Rome. The text aims to recover a leading figure of journalist and scholar, owner of an incredibly modern writing and of a rare intellectual honesty, free of political conditions and ideological prejudices, the person who describes an 'Italia della vergogna' 'expression that frequently appears in his writings' that many, often, try not to see

Scalable cover song identification based on melody indexing

In this work, we describe an efficient method for cover song identification focusing our target on pop and rock music genres. The procedure proposed is based on the fact that every pop/rock song has usually a main melody or a easily recognizing theme inside. Usually this theme or this melody, even if the cover song is really different from the original, is present in every version of the original song. This means that if we can identify the melody in each song we can identify also the original songope

Urban iconography of conflict. An historical legacy in a city in transformation

Ponència presentada a la sessió

Grating-Coupled Surface Plasmon Resonance (GC-SPR) Optimization for Phase-Interrogation Biosensing in a Microfluidic Chamber.

Surface Plasmon Resonance (SPR)-based sensors have the advantage of being label-free, enzyme-free and real-time. However, their spreading in multidisciplinary research is still mostly limited to prism-coupled devices. Plasmonic gratings, combined with a simple and cost-effective instrumentation, have been poorly developed compared to prism-coupled system mainly due to their lower sensitivity. Here we describe the optimization and signal enhancement of a sensing platform based on phase-interrogation method, which entails the exploitation of a nanostructured sensor. This technique is particularly suitable for integration of the plasmonic sensor in a lab-on-a-chip platform and can be used in a microfluidic chamber to ease the sensing procedures and limit the injected volume. The careful optimization of most suitable experimental parameters by numerical simulations leads to a 30–50% enhancement of SPR response, opening new possibilities for applications in the biomedical research field while maintaining the ease and versatility of the configuration

Urban iconography of conflict. Tales from a city in transformation

Ponència presentada a: Session 8: Post-ocupación / Post-occupancy: buildings and citie

Total angular momentum sorting in the telecom infrared with silicon Pancharatnam-Berry transformation optics

Parallel sorting of orbital angular momentum (OAM) and polarization has recently acquired paramount importance and interest in a wide range of fields ranging from telecommunications to high-dimensional quantum cryptography. Due to their inherently polarization-sensitive optical response, optical elements acting on the geometric phase prove to be useful for processing structured light beams with orthogonal polarization states by means of a single optical platform. In this work, we present the design, fabrication and test of a Pancharatnam-Berry optical element in silicon implementing a log-pol optical transformation at 1310 nm for the realization of an OAM sorter based on the conformal mapping between angular and linear momentum states. The metasurface is realized in the form of continuously-variant subwavelength gratings, providing high-resolution in the definition of the phase pattern. A hybrid device is fabricated assembling the metasurface for the geometric phase control with multi-level diffractive optics for the polarization-independent manipulation of the dynamic phase. The optical characterization confirms the capability to sort orbital angular momentum and circular polarization at the same time.Comment: 15 pages, 10 figure