Istituto Nazionale di Ottica

Abstract Optical cavities with moving mirrors provide a versatile platform for exploring radiation-matter interactions and optically mediated mechanical effects, whose control has wide technological implications. However, capturing the coupled dynamics of the electromagnetic field and of the mirror within a consistent theoretical framework remains challenging. We analyze the problem of the coupling between classical electromagnetic fields in a cavity and a movable mirror, considering both nonrelativistic and relativistic regimes of motion. Starting from the equations of motion for a mirror subject to a generic external potential, we provide a variational formulation of the mirror-radiation interaction. Within this framework, a single-mode variational approximation is introduced, which captures the essential dynamical features of the coupled system. In the special case of a mirror undergoing free motion, the variational method yields an exact solution. This unified treatment highlights the connection between different dynamical regimes and provides a basis for analyzing applications ranging from precision interferometry to relativistic radiation-pressure effects.

Metalens technology is rapidly advancing the frontiers of optical imaging by enabling flat, lightweight, and multifunctional alternatives to conventional refractive elements. Recent progress in improving efficiency, chromatic dispersion control, and scalable fabrication has positioned metalenses as pivotal components of next-generation optical platforms. In the first part of this review, we survey key developments in metalens design that address long-standing challenges in optics, including chromatic aberration, high-numerical-aperture focusing, and correction of higher-order aberrations such as spherical aberration and astigmatism. We then explore their integration into advanced imaging modalities, specifically multispectral, hyperspectral, and polarimetric systems, highlighting their role in enhancing imaging quality and operational capability. Finally, we discuss emerging applications in passive depth sensing, edge-enhanced imaging, and hybrid computational architectures, where deep neural networks are leveraged to restore broadband metalens-acquired images. Collectively, these innovations mark a paradigm shift in imaging science, with far-reaching implications for consumer optics, biomedical instrumentation, and industrial metrology, where compactness, performance, and integrability are paramount.

We investigate the two-dimensional motion of a single vortex orbiting a pinned anti-vortex in a unitary Fermi superfluid. By analyzing its trajectory, we measure the yet-unknown longitudinal and transverse mutual friction coefficients, which quantify the vortex-mediated coupling between the normal and superfluid components. Both coefficients increase while approaching the superfluid transition. They provide access to the vortex Hall angle, which is linked to the relaxation time of the localized quasiparticles occupying Andreev bound states within the vortex core, and to the vortex Reynolds number Reα associated with the transition from laminar to quantum turbulent flows. We compare our results with numerical simulations and an analytic model originally formulated for superfluid 3He, finding good agreement. Our work suggests that vortex dynamics in unitary Fermi superfluids is essentially affected by the interplay between delocalized thermal excitations and vortex-bound quasiparticles. Further, it provides a novel testbed for studying vortex dynamics at finite temperatures.

Examining the composition of aerosols in Antarctic ice cores can provide insights into past atmospheric circulation. However, interpreting this data requires an understanding of the characteristics and variability of present-day aerosols over time. In 2019, we performed the first year-round, multiparametric optical characterisation of atmospheric aerosols at Concordia Station in East Antarctica using OPTAIR, a novel instrument based on the Single Particle Extinction and Scattering (SPES) technique. We compared this data with the chemical composition of PM10 samples collected at the site and with meteorological data. We also compared it with synchronous data from a LIDAR and a ceilometer operating at Concordia Station. Significant temporal irregularities were observed in the atmospheric aerosol load, with more than one-third of the particles being dry-deposited during brief air mass subsidence events (‘spikes’), which mainly occurred in winter. The aerosol particles detected during these events were primarily composed of sea salt. Their optical properties differ significantly depending on whether they originate from frost flowers or the open ocean. Due to the intermittent nature of aerosol advection to Antarctica and its radiative effect, we estimate that glaciological, time-integrated samples may lead to an overestimation of light extinction by a factor of 3.5 or more.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-23538-2.

<strong class="journal-contentHeaderColor">Abstract.</strong> Over Antarctica, the identification of cloud layers from infrared satellite observations is extremely challenging due to the similarities in temperatures and radiative properties of the clouds and the underlying iced surfaces. Ground-based observations, collected by the Radiation Explorer in the Far InfraRed &ndash; Prototype for Applications and Development (REFIR-PAD) spectroradiometer operating at Concordia Station, Dome C, on the Antarctic Plateau are used to obtain scene classifications with the Cloud Identification and Classification (CIC) algorithm. The resulting cloud occurrence time series span the timeframe 2014&ndash;2020 showing cycles of 12 months (with maxima in December) and 6 months (with maxima in January and July), providing evidence of the semiannual oscillation of the Southern Hemisphere also in localized cloud occurrence. Similar harmonics are observed in the collocated surface temperature and pressure. Analysis of the cloud radiative effect shows that the far infrared downwelling radiance during the peaks of the semiannual oscillation is about twice as high as during its minima. Ground-based cloud classifications are compared to satellite-derived products of the Infrared Atmospheric Sounding Interferometer (IASI) flying on MetOp A, B, and C. Several IASI L2 cloud products (namely cloud tests, cloudiness summary and cloud phase) collocated with the Concordia Station geolocation are considered. The comparison regards more than 1,200 satellite observations from 2014 to 2020, and is conducted by means of a "one-to-one" correlation analysis and via the analysis of the observed cloud occurrences. The one-to-one analysis (conducted using temporally and spatially collocated measurements from IASI and REFIR-PAD) shows that, up to December 2019, the IASI products <em>Artificial Neural Network</em> (<em>ANN</em>) test and the <em>Advanced Very-High-Resolution Radiometer</em> (<em>AVHRR</em>) <em>heterogeneity</em> test are moderately correlated with ground classifications, while the <em>Numerical Weather Prediction</em> (<em>NWP</em>) test, <em>AVHRR</em> c<em>loud fraction test</em>, and flag <em>cldnes</em> are mostly anticorrelated. However, from December 2019, both the <em>NWP</em> test and the flag <em>cldnes</em> switch to positive correlation values. When the flag <em>cloud phase</em> is used as a scene classifier, a limited correlation is found up to December 2019 but significantly higher values are observed in 2020. Finally, it is shown that the IASI cloud phase classification (ice or mixed/liquid) is well correlated with the ground-based phase classification.

Decoherence is a manifestation of the coupling of a system with its environment. The resulting loss of information can hamper the functioning of quantum devices; hence, there is a need to understand its origin and dynamics. Decoherence can stem from entanglement, but it can also be classical in nature. Indeed, methods have been developed to understand whether qubit-environment entanglement (QEE) is actually present in some important classes of quantum channels—pure dephasing. Their practicality resides in the fact that they only require accessing the system qubit. In this paper, we show an implementation of this technique in a photonic quantum channel simulator via a scheme that has been tailored to the system under study. By controlling the input state of the environment in our simulation, we can check the occurrence of qubit environment entanglement in simple, yet insightful test cases. Our results showcase the usefulness and experimental relevance of the QEE witnessing technique.

The intensity noise of a laser source represents one of the key factors limiting the ultimate sensitivity in laser-based systems for sensing and telecommunication. For advanced applications based on interferometry, the availability of a shot-noise-limited local oscillator is even more important for the effective feasibility of high-precision measurements. This is particularly crucial in quantum optics applications based on homodyne detection schemes to measure non-classical light states, such as squeezed states. This work deeply investigates and analyzes the intensity noise features of the most widely used mid-infrared semiconductor heterostructured lasers: quantum cascade and interband cascade lasers. For this purpose, a comprehensive comparison of three different continuous-wave lasers operating at room temperature around 4.5 µm wavelength is presented. First, a thorough electro-optical characterization is given, highlighting the differences and the shared common characteristics of the tested devices. Then, a detailed intensity noise analysis is reported, identifying their different noise operations with a particular reference to shot-noise-limited operations. Finally, some perspectives towards advanced applications are discussed.

Epsilon near zero(ENZ) thin films have attracted considerableattention due to their unique optical properties in the near-infrared(NIR), which have enabled a wide range of interesting phenomena anddiverse applications. In nonlinear optics, the near-zero permittivityof films in the NIR region has been shown to enhance second-ordernonlinear processes by several orders of magnitude, therefore boostingboth second harmonic (SH) generation and broadband THz generation.In this work, we investigate THz-field-induced second harmonic (TFISH)generation in indium tin oxide (ITO) thin films in the ENZ spectralregion. A symmetry-breaking electric field is applied using a highfield strength broadband THz pulse, which when temporally overlappedwith an ultrashort optical pulse, results in the emission of secondharmonic from the centrosymmetric film. The experimental results mirrorvery well the predictions of a four-wave mixing optical model, capturingthe interplay between linear and nonlinear effects driving the NIR-THz-ITOinteraction.