Photonics

We are interested in production and accurate manipulation of light and in its interaction with matter under different forms. Our main fields of research involve the study of the optical properties and light transport in complex mesoscopic systems, ranging from random to periodic ones (e.g. from powders or colloidal suspensions to photonic bandgap crystals); the precise manipulation of light at the single-photon level and its implications for fundamental physics and new technologies; the control of photonic nanocavities by near field manipulation and the quantum electrodynamic effects of single semiconductor nanoemitters; all kinds of interactions between light and matter, in particular for the development of novel light sources and spectroscopic techniques into new, and almost unexplored, spectral regions, from the THz to the extreme UV. We are also interested in the applications of such novel methodologies for the realization of new photonic devices such as optical switches, quantum logic gates, light sources, and photonic circuits, and experimental settings for precise metrology or quantum simulations.
A series of workshops about micro- and nanophotonics is an ongoing training.

Optics of complex system

Disorder in matter can induce remarkable interference effects, that may result in cancellation of the diffusion coefficient and so in a strong localization phenomenon. First described for Schrödinger waves, this so-called Anderson localization has very general validity and it has the extraordinary property that, when it occurs, diffusive transport comes to a halt and a disordered material starts to behave as an insulator. The occurrence of this phenomenon strongly depends on dimensionality of sample: we are focusing on 2d systems where localization effect can increase the optical thickness of material and so it can be useful to design novel photovoltaic panels. Another research line concerns super-diffusive transport of light in a new class of entirely homemade material called Lévy glass, in which density of scatterers is strongly inhomogeneous due to the inclusion of a well-chosen distribution of index-matched spheres in the scattering medium.
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Nano photonics

Photonic crystals are materials characterized by a periodical modulation of the refractive index of the same order of magnitude of the wavelength used to investigate them. Due to multiple internal reflections and refractions, interference phenomena occur and under certain conditions the scattering at the dielectric interface can cause the formation of frequency regions where the propagation of light is inhibited for some particular directions. These frequency regions are called Photonic Band Gaps (PBG) and by introducing a defect in the periodicity of crystals it is possible to obtain a state inside them where light is spatially confined and consequently the defect can be exploited for example as a nano-cavity. Main tool of this research team is near-field optical microscopy (SNOM), that permits not only to get information about the optical properties of these structures, but it also allows to locally modify their optical behavior in order to design optoelectronic or purely optical circuits.
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Solid state nanostructures

Semiconductor quantum dots (QDs) are the basic materials for the realization of high-performance optoelectronic devices and they can be also useful as building blocks for spintronic devices and for the creation and manipulation of quantum bits at the nanoscale. Several promising applications in these fields, such as single photon sources for quantum cryptography, quantum bits or quantum logical elements, require the coherent manipulation of the carrier population in the adjacent QDs. We are currently addressing several QDs frontier topics by means of time integrated/time resolved optical spectroscopy, confocal microscopy, photon coincidence measurements and micro-photoluminescence experiments. Other research lines concern the realization and characterization of GaN-based UV emitters, magnetic nanostructured systems, TiO2 nanoparticles. Main applications are optoelectronic devices and the new generation of solar cells.
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Extreme optics

The adjective extreme in the name of this topic is related to both the wavelengths and the number of photons used in the experiments, jointly performed with INO-CNR. Our research tools range from ultra-intense laser pulses to single photons, from ultra-broadband supercontinuum sources to radiation on the extreme ultraviolet (XUV) end of the electromagnetic spectrum. On one side, ultrashort and ultraintense laser pulses are used to produce highly-nonlinear interactions with matter. This has led to fundamental studies on supercontinuum sources and to the production of coherent radiation in the XUV in the form of high-order laser harmonics. The latter is a simple and cost-effective alternative to synchrotron facilities, with applications to plasma interferometry and to novel types of XUV spectroscopy. On the other side, the ability to arbitrarily manipulate and characterize light at the single-photon level is allowing us to perform experiments on the foundations of quantum mechanics, and to develop new tools for emerging quantum technologies.
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Non-linear optics and precision spectroscopy
The goal of precision drives our experimental activity for spectroscopy and the development of nonlinear sources. First of all, precision in measuring optical frequencies was pushed ahead by the advent of the optical frequency combs, that are real rulers of light enabling to count the oscillations of any laser field with unprecedented accuracy. But precision, also, in the measurement of any tiny effect that the interaction between light and matter may produce. Therefore, we exploit the non-linear interactions between light and crystals (such as lithium-niobate) to generate light in frontier spectral regions, as mid-IR or THz, or to convert frequencies. Infrared light is, indeed, a unique tool for harnessing molecules, since most of their fundamental ro-vibrational and rotational bands lie in the mid and far infrared. For this reason, we combine state-of-the-art sources (such as mid-IR and THz Quantum Cascade Lasers) with advanced spectroscopic techniques (such as the recently developed Saturated-Absorption Cavity Ring-down-SCAR technique) for ultra-high sensitivity trace gas detection, metrological-grade applications and fundamental studies on molecules.
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Organic molecules for Quantum Optics

The focus of our activity on molecules for quantum optics is the combination of advanced photonic materials with organic molecules, with the idea of developing novel light-matter interfaces for quantum technologies. Single-molecule-based photon sources can be selectively coupled to the evanescent electromagnetic field of plasmonic excitations, graphene, or complex dielectric media. The system hence represents a valuable testbed for applications ranging from microscale opto-electronics, to fluorescence-based sensing and solid-state protocols for quantum communication. The group is also working on the coupling of single molecule to the Atom-Chip condensate.
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Color centers in diamond for quantum optics and metrology

The development of novel quantum technologies depends on the knowledge and control of single quantum systems (atom, ion, photon) and their interfaces. A number of structures has emerged as single atom-like quantum systems in solid-state physics. Our research activity focuses on color centers in diamond, i.e. single localized defects in the diamond lattice, with specific interest in spin quantum dynamics and control, and single-photon emission. Our interest concerns the development of scalable quantum registers in diamond for information and computation process, the definition of metrology standards, and the implementation of quantum sensors, with extremely high sensitivity and spatial resolution thanks to the realization of nanoscale devices.
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