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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - PHOSPhOR (Photonics of Spin–Orbit Optical Phenomena)

Teaser

Light, or more generally the optical electromagnetic field, has two important properties, phase and polarization, both not visible to the naked eye. The phase structure in space determines the light subsequent propagation, while the polarization is mainly important in the...

Summary

Light, or more generally the optical electromagnetic field, has two important properties, phase and polarization, both not visible to the naked eye. The phase structure in space determines the light subsequent propagation, while the polarization is mainly important in the interaction with matter. For a single quantum particle of light – the photon – the phase spatial structure is sometimes defined as the “orbital” degrees of freedom, as it defines the photon trajectories, while the polarization is related to the “spin” degree of freedom, which could be visualized as an intrinsic rotation of the photon. In most optical phenomena, these two degrees of freedom are rather independent, but recently, a growing number of systems is being discovered, or artificially engineered, in which the photon spin-orbit interactions are important. PHOSPhOR is aimed at investigating these interactions and exploiting them for enhancing our control of the light spatial and temporal structure, with possible benefits for a number of applications, including optical communication, quantum information technology, photo lithography, etc.

PHOSPhOR vision is to promote the development of a full-fledged spin-orbit photonic science and technology, in which the vector states of structured light beams, optical pulses and even quantum states of individual photons can be precisely tailored and manipulated in all their aspects and used, in combination with suitable material systems, to obtain new classical- or quantum-optical functionalities, or exploited as scientific tools to investigate new physical phenomena.

Work performed

During the first half of the project, we obtained a number of important results. We mention here briefly the most significant ones.

A first very important result has been the introduction of a new fundamental principle for light lateral confinement and guiding, entirely based on spin-orbit interactions. This new concept, which we proposed and demonstrated experimentally, relies on using polarization manipulations to introduce the optical phases needed to achieve waveguiding.

Another significant result has been the first demonstration of the tunable quantum interference between two photons characterized by a complex polarization pattern. Quantum interference is a fundamental ingredient for quantum information technology and quantum computing, as it enables protocols like teleportation and entanglement swapping. Two-photon quantum interference for structured light involving complex polarization patterns had not been demonstrated yet. This gap has now been filled by exploiting a device based on spin-orbit photonic interactions. This result could enable a fuller exploitation of the potential of structured light in the quantum regime. Being based on a compact device, this technique can also be suitable for integration as a building block in future complex quantum networks.

Third, we ideated and developed a new photonic technology for quantum simulations based on using a suitable sequence of optical elements that exploit spin-orbit interactions to control the internal spatial structure of a single optical beam. The evolution of the light beam in such system can be proved to be equivalent to that of a particle performing a “quantum walk” in a suitable environment. This concept can be applied in various directions. We focused our quantum-simulation work on investigating topological physics and, in particular, demonstrated new methods for measuring the underlying topological invariants by observing the time evolution of the particle in the system bulk. The most recent results of this line of research include an upgrade to the simulation of two-dimensional quantum systems (while previous ones were limited to 1D systems). A patent application on this new photonic technology has been filed.

A fourth important line of research has been the use of femtosecond pulses tailored in their polarization structure by a suitable spin-orbit optical element, in order to imprint a complex surface pattern to certain solid materials. The imprinting technique is based on femtosecond laser ablation, which is an interesting phenomenon per se.

Finally, the PHOSPhOR team organized the 4th International Conference on Optical Angular Momentum, which was held in Anacapri (Italy) on 18-22 September 2017 (ICOAM17).

Final results

The most significant results reported in the previous sections are all clear progresses beyond the state of the art existing before the start of this project. Until the end of the project we hope to achieve all of the following major objectives that were originally planned for PHOSPhOR:

We plan to develop innovative systems based on spin-orbit optical media for generating light fields with a complex spatial vector structure, both in 2D and 3D. Moreover, we aim at extending these ideas and methods to other spectral domains, such as terahertz or UV, and at exploring the many classical-photonics applications of these devices.

We plan to exploit the spin-orbit correlations generated within single photons and/or among few correlated photons to demonstrate novel quantum-information protocols. Engineered spin-orbit photonic processes at the single photon level will be used for the implementation of quantum simulations of material systems, and in particular topological quantum phases and phase transitions.

We plan to develop 3D-structured dielectric photonic media that exploit spin-orbit interactions to mold the optical propagation and dispersion properties. We also plan to investigate novel physical processes occurring in light-sensitive material systems which respond both to the optical polarization and to its spatial inhomogeneity, with the added purpose of measuring and reconstructing arbitrary complex vector fields.

Website & more info

More info: http://www.slamgroup.it/index.php/funding.