arXiv subjects

F. Chiossi

Publications and source records attributed to F. Chiossi.

7 recordsLinked to original sources

arXiv2019

Spontaneous formation of a macroscopically extended coherent state

It is a straightforward result of electromagnetism that dipole oscillators radiate more strongly when they are synchronized, and that if there are $N$ dipoles, the overall emitted intensity scales with $N^2$. In atomic physics, such an enhanced radiative property appears when coherence among two-level identical atoms is established, and is well-known as "superradiance" \cite{Dicke:1954aa}. In superfluorescence (SF), atomic coherence develops via a self-organisation process stemming from the common radiated field, starting from a incoherently prepared population inversion \cite{Bonifacio:1975aa}. First demonstrated in a gas \cite{Skribanowitz:1973} and later in condensed matter systems \cite{Florian:1984}, its potential is currently being investigated in the fields of ultranarrow linewidth laser development for fundamental tests in physics \cite{Meiser:2009,Meiser:2010,Bohnet:2012aa,Norcia:2016, Norcia:2018}, and for the development of devices enabling entangled multi-photon quantum light sources \cite{Raino:2018aa,Angerer:2018aa}. A barely developed aspect in superradiance is related to the properties of the dipole array that generates the pulsed radiation field. In this work we establish the experimental conditions for formation of a macroscopic dipole via superfluorescence, involving the remarkable number of $4\times10^{12}$ atoms. Even though rapidly evolving in time, it represents a flexible test-bed in quantum optics. Self-driven atom dynamics, without the mediation of cavity QED nor quantum dots or quantum well structures, is observed in a cryogenically-cooled rare-earth doped material. We present clear evidence of a decay rate that is enhanced by more than 1-million times compared to that of independently emitting atoms. We thoroughly resolve the dynamics by directly measuring the intensity of the emitted radiation as a function of time.

physics.optics↗

arXiv2019

GaAs as a bright cryogenic scintillator for the direct dark matter detection

The optical and scintillation properties of undoped, Si-doped, and Si, B co-doped GaAs samples were studied. The light yield specification and X-ray luminescence of GaAs over a wide IR region by using Si and InGaAs photodetectors are presented. The undoped GaAs demonstrated a narrow emission band at 838 nm (1.48 eV) and a low light output of about 2 ph/keV. The GaAs:Si is characterized by three broad luminescence bands at 830 nm (1.49 eV), 1070 nm (1.16 eV), 1335 nm (0.93 eV) and a light output of about 71 ph/keV. In the case of GaAs:(Si, B), four luminescence bands at 860 nm (1.44 eV), 930 nm (1.33 eV), 1070 nm (1.16 eV) and 1335 nm (0.93 eV) were observed. A high light yield higher than 125 ph/keV was estimated for the co-doped sample. The applications of low energy gap semiconductors as cryogenic scintillators for particle detection are discussed. The GaAs is a promising crystal for a cryogenic scintillator for the dark matter (DM) detection.

physics.ins-det↗

arXiv2018

Infrared and visible scintillation of Ho$^{3+}$-doped YAG and YLF crystals

In our effort to develop a new kind of detector for low-energy, low-rate energy deposition events we have investigated the cathodo- and radioluminescence of Ho:YAG and Ho:YLF single crystals in an extended wavelength range from $200\,$nm to $2200\,$nm. The emission spectra of both crystals show a much more intense emission in the infrared range than in the visible one. We estimate an infrared light yield of $40\,$photons/keV when exciting the crystals with X-rays of energy $\approx 30\,$keV. The main reason of this high value is due to the Ho$^{3+}$ ions energy levels scheme that allows efficient cross relaxation processes to occur even at low dopant concentration.

physics.atom-ph↗

arXiv2017

Laser induced fluorescence for axion dark matter detection: a feasibility study in YLiF$_4$:Er$^{3+}$

We present a detection scheme to search for QCD axion dark matter, that is based on a direct interaction between axions and electrons explicitly predicted by DFSZ axion models. The local axion dark matter field shall drive transitions between Zeeman-split atomic levels separated by the axion rest mass energy $m_a c^2$. Axion-related excitations are then detected with an upconversion scheme involving a pump laser that converts the absorbed axion energy ($\sim $ hundreds of $μ$eV) to visible or infrared photons, where single photon detection is an established technique. The proposed scheme involves rare-earth ions doped into solid-state crystalline materials, and the optical transitions take place between energy levels of $4f^N$ electron configuration. Beyond discussing theoretical aspects and requirements to achieve a cosmologically relevant sensitivity, especially in terms of spectroscopic material properties, we experimentally investigate backgrounds due to the pump laser at temperatures in the range $1.9-4.2$ K. Our results rule out excitation of the upper Zeeman component of the ground state by laser-related heating effects, and are of some help in optimizing activated material parameters to suppress the multiphonon-assisted Stokes fluorescence.

astro-ph.CO↗

arXiv2017

Cathodo- and radioluminescence of Tm$^{3+}$:YAG and Nd$^{3+}$:YAG in an extended wavelength range

We have studied the cathodo- and radioluminescence of Nd:YAG and of Tm:YAG single crystals in an extended wavelength range up to $\approx 5\,μ$m in view of developing a new kind of detector for low-energy, low-rate energy deposition events. Whereas the light yield in the visible range is as large as $\approx 10^{4}\,$photons/MeV, in good agreement with literature results, in the infrared range we have found a light yield $\approx 5\times 10^{4}\,$photons/MeV, thereby proving that ionizing radiation is particularly efficient in populating the low lying levels of rare earth doped crystals.

physics.optics↗

arXiv2016

A new technique for infrared scintillation measurements

We propose a new technique to measure the infrared scintillation light yield of rare earth (RE) doped crystals by comparing it to near UV-visible scintillation of a calibrated Pr:(Lu$_{0.75}$Y$_{0.25}$)$_{3}$Al$_5$O$_{12}$ sample. As an example, we apply this technique to provide the light yield in visible and infrared range up to \SI{1700}{nm} of this crystal.

physics.ins-det↗

arXiv2015

Particle detection through the quantum counter concept in YAG:Er$^{3+}$

We report about a novel scheme for particle detection based on the infrared quantum counter concept. Its operation consists of a two-step excitation process of a four level system, that can be realized in rare earth-doped crystals when a cw pump laser is tuned to the transition from the second to the fourth level. The incident particle raises the atoms of the active material into a low lying, metastable energy state, triggering the absorption of the pump laser to a higher level. Following a rapid non-radiative decay to a fluorescent level, an optical signal is observed with a conventional detectors. In order to demonstrate the feasibility of such a scheme, we have investigated the emission from the fluorescent level $^4$S$_{3/2}$ (540 nm band) in an Er$^{3+}$-doped YAG crystal pumped by a tunable titanium sapphire laser when it is irradiated with 60 keV electrons delivered by an electron gun. We have obtained a clear signature this excitation increases the $^{4}I_{13/2}$ metastable level population that can efficiently be exploited to generate a detectable optical signal.

physics.ins-det↗