Cascade Superfluorescence in Er:YLF

We report the analysis of paired photon pulses arising from two cascading transitions in continuously pumped Erbium-doped YLiF$_4$ 1% and 0.01% crystals at 1.6 K. The dependence of the pulse peak intensity on the squared number of involved Erbium ions, between 10$^{11}$ and 10$^{13}$, definitely identifies the cooperative nature of the two pulsed emissions, that are generated by the subsequent, spontaneous formation of coherent states. The observed fluctuations of the time interval between the paired pulses and, most importantly, its correlation with the second pulse duration, demonstrate that the Erbium ions coherence is indeed seeded by vacuum fluctuations

Superfluorescence from Erbium-doped crystals

In Superfluorescence process, an initially incoherent ensemble of excited atoms (molecules, etc) gives rise to a macroscopic polarization due to spontaneously synchronization of the atomic dipoles. In this coupled system, every single dipole is correlated with all the others and the atomic transition rate is enhanced by a factor μN, with N the number of correlated atoms and μ a geometrical factor that accounts for the interference effects. The cooperative radiative decay results in the emission of coherent photon bunches whose peak intensity is proportional to μN^2 and the duration scales with (μN)^−1. In this thesis, we present the clear signatures of the Superfluorescence from Erbium-doped Y2SiO5 and YLiF4 crystals at liquid helium temperature. The process is observed for two transitions and involves the remarkable number of 10^12 Erbium ions, accelerating the radiative decay by millions of times. Several aspects of Superfluorescence are deeply investigated and a remarkable agreement with the theoretical expectation is reported

Superfluorescence from Erbium-doped crystals

In Superfluorescence process, an initially incoherent ensemble of excited atoms (molecules, etc) gives rise to a macroscopic polarization due to spontaneously synchronization of the atomic dipoles. In this coupled system, every single dipole is correlated with all the others and the atomic transition rate is enhanced by a factor μN, with N the number of correlated atoms and μ a geometrical factor that accounts for the interference effects. The cooperative radiative decay results in the emission of coherent photon bunches whose peak intensity is proportional to μN^2 and the duration scales with (μN)^−1. In this thesis, we present the clear signatures of the Superfluorescence from Erbium-doped Y2SiO5 and YLiF4 crystals at liquid helium temperature. The process is observed for two transitions and involves the remarkable number of 10^12 Erbium ions, accelerating the radiative decay by millions of times. Several aspects of Superfluorescence are deeply investigated and a remarkable agreement with the theoretical expectation is reported

Misure di luminescenza nel vicino infrarosso e nel visibile di Nd3+:YAG eccitati per impatto elettronico

Si è misurata la luminescenza infrarossa (Evis) di cristalli di Nd3+:YAG eccitati per bombardamento con elettroni ai fini dello sviluppo di un rivelatore di radiazioni ionizzanti. Lo spettro osservato è confrontato con quello ottenuto per eccitazione laser. Si è misurata anche l'efficenza di emissione (IR)

New ideas on prospective low energy threshold detectors for dark matter searches

Low energy threshold detectors are necessary in many frontier fields of experimental physics. In particular, these are extremely important for probing possible dark matter (DM) candidates. We present a novel detection approach that exploits the energy levels of atoms maintained at cryogenic temperature. We exploit laser-assisted transitions that are triggered by the absorption of the incident particle in the material and lead to the emission of a fluorescent photon or an electron. In this approach, the incident particle will in fact excite the first low-lying energy level that is then up-converted using an opportune narrow-band laser system. Two different detection schemes are thus possible in our active material: one is based on a photon signal while the other takes advantage of high efficiency in-vacuum charge detection

Mode of birth in women with low-lying placenta: protocol for a prospective multicentre 1:3 matched case-control study in Italy (the MODEL-PLACENTA study)

Introduction: The term placenta praevia defines a placenta that lies over the internal os, whereas the term low-lying placenta identifies a placenta that is partially implanted in the lower uterine segment with the inferior placental edge located at 1-20 mm from the internal cervical os (internal-os-distance). The most appropriate mode of birth in women with low-lying placenta is still controversial, with the majority of them undergoing caesarean section. The current project aims to evaluate the rate of vaginal birth and caesarean section in labour due to bleeding by offering a trial of labour to all women with an internal-os-distance >5 mm as assessed by transvaginal sonography in the late third trimester. Methods and analysis: The MODEL-PLACENTA is a prospective, multicentre, 1:3 matched case-control study involving 17 Maternity Units across Lombardy and Emilia-Romagna regions, Italy. The study includes women with a placenta located in the lower uterine segment at the second trimester scan. Women with a normally located placenta will be enrolled as controls. A sample size of 30 women with an internal-os-distance >5 mm at the late third trimester scan is needed at each participating Unit. Since the incidence of low-lying placenta decreases from 2% in the second trimester to 0.4% at the end of pregnancy, 150 women should be recruited at each centre at the second trimester scan. A vaginal birth rate ≥60% in women with an internal-os-distance >5 mm will be considered appropriate to start routinely admitting to labour these women. Ethics and dissemination: Ethical approval for the study was given by the Brianza Ethics Committee (No 3157, 2019). Written informed consent will be obtained from study participants. Results will be disseminated by publication in peer-reviewed journals and presentation in international conferences. Trial registration number: NCT04827433 (pre-results stage)