In recent years, research in optics and photonics produced many forms of structured light for different applications, such as optical trapping, telecommunication, and imaging. Generating such beams usually requires challenging control of phase, amplitude, and polarization, and often more than one phase plate is needed. Mounting such optical elements leads to lengthy alignment procedures, worsened by tight tolerances and complex beam shapes. Here we present a method for fabricating two aligned metalenses on the two surfaces of a substrate, halving therefore the degrees of freedom for alignment. Such method is shown to work for a device capable of multiplying the topological charge of an OAM beam.
The ability to generate structured light with arbitrarily controlled polarization in a compact optical path has been a challenge over the last few years in the fields of optics and photonics. In this regard, our work proposes the design, fabrication, and characterization of new dielectric dual-functional meta-optics that generate orbital angular momentum beams with on-demand different vectorial behaviors acting only on the input polarization. The metaoptics are designed as an array of periodic subwavelength metastructures (so-called meta-atoms) composed of silicon nanofins on a silicon substrate, acting like half-wave plates that exploit both the geometric and dynamic phases. We prove the generation of dual-ring perfect vector beams and novel complex vectorial configurations: azimuthally-variant perfect vector beams and helico-conical vector beams. This design solution offers both compactness of the optical path and easy integration with other optical elements, suggesting intriguing applications in telecommunications, imaging, particle manipulation, and quantum information.
Over the past few years, the optics and photonics field has faced a challenge in developing the capability to produce structured light with arbitrary controlled polarization in a compact optical path. Our research addresses this challenge by presenting a novel approach involving the design of dielectric dual-functional metaoptics. These miniature, high-resolution metaoptics can generate custom elliptical orbital angular momentum beams with varied behaviors based on the input light's polarization. Our approach enhances the compactness of optical paths and facilitates seamless integration with other optical elements. Specifically, the proposed metaoptics exhibit suitability for applications in particle manipulation, microscopy, high-capacity communications, and security by contributing to complex structured light generation.
Among the fourth-generation light sources, the Italian free-electron laser (FEL) FERMI is the only one operating in the high-gain harmonic generation (HGHG) seeding mode. FERMI delivers pulses characterized by a quasi transform limited temporal structure, photon energies lying in the extreme ultra-violet (EUV) region, supreme transversal and longitudinal coherences, high peak brilliance, and full control of the polarization. Such state of the art performances recently opened the doors to a new class of time-resolved spectroscopies, difficult or even impossible to be performed using self-amplified spontaneous sources (SASE) light sources. FERMI is currently equipped with three operating beamlines opened to external users (DiProI, LDM and EIS), while two more are under commissioning (MagneDYN and TeraFERMI). Here, we present the recent highlights of the EIS (Elastic and Inelastic Scattering) beamline, which has been purposely designed to take full advantage from the coherence, the intensity, the harmonics content, and the temporal duration of the pulses. EIS is a flexible experimental facility for time-resolved EUV scattering experiments on condensed matter systems, consisting of two independent end-stations. The first one (EIS-TIMEX) aims to study materials in metastable and warm dense matter (WDM) conditions, while the second end-station (EIS-TIMER) is fully oriented to the extension of four-wave mixing (FWM) spectroscopies towards the EUV spectral regions, trying to reveal the behavior of matter in portions of the mesoscopic regime of exchanged momentum impossible to be probed using conventional light sources.
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