scholarly journals Optical Polarimetry for Fundamental Physics

Universe ◽  
2021 ◽  
Vol 7 (7) ◽  
pp. 252
Author(s):  
Guido Zavattini ◽  
Federico Della Valle
Keyword(s):  
Signal To Noise Ratio ◽  
Optical Cavity ◽  
Heterodyne Detection ◽  
Optical Scheme ◽  
Dipole Magnet ◽  
Fundamental Physics ◽  
Noise Floor ◽  
Electron Positron ◽  
Strong Candidate ◽  
Virtual Pairs

Sensitive magneto-optical polarimetry was proposed by E. Iacopini and E. Zavattini in 1979 to detect vacuum electrodynamic non-linearity, in particular Vacuum Magnetic Birefringence (VMB). This process is predicted in QED via the fluctuation of electron–positron virtual pairs but can also be due to hypothetical Axion-Like Particles (ALPs) and/or MilliCharged Particles (MCP). Today ALPs are considered a strong candidate for Dark Matter. Starting in 1992 the PVLAS collaboration, financed by INFN, Italy, attempted to measure VMB conceptually following the original 1979 scheme based on an optical cavity permeated by a time-dependent magnetic field and heterodyne detection. Two setups followed differing basically in the magnet: the first using a rotating superconducting 5.5 T dipole magnet at the Laboratori Nazionali di Legnaro, Legnaro, Italy and the second using two rotating permanent 2.5 T dipole magnets at the INFN section of Ferrara. At present PVLAS is the experiment which has set the best limit in VMB reaching a noise floor within a factor 7 of the predicted QED signal: Δn(QED)=2.5×10−23 @ 2.5 T. It was also shown that the noise floor was due to the optical cavity and a larger magnet is the only solution to increase the signal to noise ratio. The PVLAS experiment ended at the end of 2018. A new effort, VMB@CERN, which plans to use a spare LHC dipole magnet at CERN with a new modified optical scheme, is now being proposed. In this review, a detailed description of the PVLAS effort and the comprehension of its limits leading to a new proposal will be given.

scholarly journals Performance of Optical Mobile Communications with User Mobility and Multiple Light Sources

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Jian Dang ◽  
Jiajun Gao ◽  
Zaichen Zhang ◽  
Liang Wu ◽  
Bingcheng Zhu ◽  
...  
Keyword(s):  
Mobile Communications ◽  
High Speed ◽  
Signal To Noise Ratio ◽  
High Signal ◽  
Light Sources ◽  
Optical Scheme ◽  
User Mobility ◽  
Optical Wireless ◽  
Free Space Optical ◽  
User Grouping

Optical mobile communication (OMC) is a recently proposed optical wireless communication concept aiming to provide very high-speed data rate optical wireless links for multiple and, in general, distributed mobile users. Previous work analyzed the rate performance of a two-user OMC system without user mobility. This paper extends the rate analysis to multiple users with mobility. The scenario of employing multiple light sources with possible user grouping is also considered. User mobility and multiple light sources lead to new challenges on the system design which are addressed for broadcast downlink communication in this work. Simulations show that user mobility decreases the rate, and the way of how to utilize multiple light sources has great impact on the performance. In particular, simultaneous power division usage of multiple light sources through user grouping and power allocation brings almost no gain as compared with the case of single light source. On the other hand, time division usage of multiple light sources is capable of compensating for the hardware deficiency and thus increasing the rate greatly. It is found that OMC is not only superior to the conventional scheme with nonadjustable channel gains but also outperforms free space optical scheme at high signal-to-noise ratio region.

scholarly journals Cascaded Rf-Fso-Vlc System using Df Relays

2019 ◽  
Vol 8 (10) ◽  
pp. 4357-4362
Keyword(s):  
Direct Detection ◽  
Detection System ◽  
Signal To Noise Ratio ◽  
Visible Light Communication ◽  
Heterodyne Detection ◽  
Core Network ◽  
Free Space Optical ◽  
Error Performance ◽  
Optical Link ◽  
Detection Techniques

This paper presents performance analysis of cascaded radio frequency-free space optical communication-visible light communication (RF-FSO-VLC) system. The proposed model comprises of the RF link as the core network, a terrestrial optical link for providing last mile connectivity with the indoor cell users communicating through VLC environment. The RF link undergoes Nakagami-m distributed fading, while the terrestrial optical link is modeled by Double Generalized Gamma (DGG) distributed turbulence and Rayleigh-distributed misalignment losses. VLC links are characterized by the randomness in users’ position. Using statistical properties of system signal-to-noise ratio (SNR), outage and error performance of the proposed system is evaluated depending on whether the relays and the destination decode either perfectly or erroneously. The numerical results show that the system performance varies depending on field-of view (FOV) of the detector and user’s position. This is because as FOV increases along with the height of the LED, the outage probability of the system increases. Error probability depends on the type of detection techniques, where a heterodyne detection system performs better than a direct detection system. Moreover, through results it is inferred that severe fading and misalignment losses result in poor error performance of the considered system errors on the performance of the considered cooperative system.

Télémètre à détection coherente avec un laser CO2 à ondes entretenues : étude et conception

1983 ◽  
Vol 61 (2) ◽  
pp. 318-331 ◽  
Author(s):  
Denis Vincent ◽  
Gabriel Otis
Keyword(s):  
Detection System ◽  
Signal To Noise Ratio ◽  
Optical Power ◽  
Experimental System ◽  
Intermediate Frequency ◽  
Local Oscillator ◽  
Heterodyne Detection ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Rotating Target

We performed a theoretical and experimental study of a 10.6 μm heterodyne detection system with nonlinear postdetection. A single laser serves as both transmitter and local oscillator; the intermediate frequency is given by the Doppler effect due to a rotating target. An electrooptic crystal modulates the amplitude of the laser beam at a frequency of 15 kHz; a synchronous voltmeter measures the return signal after the nonlinear element. Values of the signal-to-noise ratio with respect to incident optical power agree with the results of the theoretical model. In particular, experimentally measured target-induced frequency spreading effects on the signal-to-noise ratio correspond to the predictions of the model. We also describe an experimental system.

scholarly journals Resolution limits of spatial mode demultiplexing with noisy detection

2020 ◽  
Vol 18 (01) ◽  
pp. 1941015 ◽  
Author(s):  
Yink Loong Len ◽  
Chandan Datta ◽  
Michał Parniak ◽  
Konrad Banaszek
Keyword(s):  
Signal To Noise Ratio ◽  
Photon Counting ◽  
Super Resolution ◽  
Spatial Separation ◽  
Heterodyne Detection ◽  
Light Sources ◽  
Spatial Mode ◽  
Detection Techniques ◽  
Resolution Imaging ◽  
Point Light

We consider the problem of estimating the spatial separation between two mutually incoherent point light sources using the super-resolution imaging technique based on spatial mode demultiplexing (SPADE) with noisy detectors. We show that in the presence of noise, the resolution of the measurement is limited by the signal-to-noise ratio (SNR) and the minimum resolvable spatial separation has a characteristic dependence of [Formula: see text]. Several detection techniques, including direct photon counting, as well as homodyne and heterodyne detection are considered.

R&D steps of a 12-T common coil dipole magnet for SPPC pre-study

2016 ◽  
Vol 31 (33) ◽  
pp. 1644018 ◽  
Author(s):  
Chengtao Wang ◽  
Kai Zhang ◽  
Qingjin Xu
Keyword(s):  
High Energy Physics ◽  
Optimization Method ◽  
High Energy ◽  
Dipole Magnet ◽  
Proton Proton ◽  
Protection Method ◽  
Electron Positron ◽  
The Common ◽  
Beijing China ◽  
Energy Physics

IHEP (the Institute of High Energy Physics, Beijing, China) has started the R&D of high field accelerator magnet technology from 2014 for recently proposed CEPC-SppC (Circular Electron Positron Collider, Super proton–proton Collider) project. The conceptual design study of a 20-T dipole magnet is ongoing with the common coil configuration, and a 12-T model magnet will be fabricated in the next two years. A 3-step R&D process has been proposed to realize this 12-T common-coil model magnet: first, a 12-T subscale magnet will be fabricated with Nb3Sn and NbTi superconductors to investigate the fabrication process and characteristics of Nb3Sn coils, then a 12-T subscale magnet will be fabricated with only Nb3Sn superconductors to test the stress management method and quench protection method of Nb3Sn coils; the final step is fabricating the 12-T common-coil dipole magnet with HTS (YBCO) and Nb3Sn superconductors to test the field optimization method of the HTS and Nb3Sn coils. The characteristics of these R&D steps will be introduced in the paper.

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