3,126 research outputs found
Erratum to: A polarisation modulation scheme for measuring vacuum magnetic birefringence with static fields (The European Physical Journal C, (2016), 76, 5, (294), 10.1140/epjc/s10052-016-4139-0)
No full textIn the original article unfortunately we missed two typos in the equation for I(δ) at the top of the fourth page of the article. © 2017, The Author(s)
Frequency locking to a high-finesse Fabry-Perot cavity of a frequency doubled Nd:YAG laser used as the optical modulator
No full textWe report on the frequency locking of a frequency doubled Nd:YAG laser to a 45 000 finesse, 87-cm-long, Fabry–Perot cavity using a modified form of the Pound–Drever–Hall technique. Necessary signals, such as light phase modulation and frequency correction feedback, are fed directly to the infrared pump laser. This is sufficient to achieve a stable locking of the 532 nm visible beam to the cavity, also showing that the doubling process does not degrade laser performances
Progress toward a direct experimental detection of γγ interactions
No full textA fundamental quantum electrodynamics prediction which has so far not yet been confirmed experimentally by a direct observation in a laboratory experiment is γγ interactions. Such a direct observation requires a scenario where both the beam and the target are made of bosons, while so far experiments have exploited matter particles as beam and/or target. A consequence of the existence of γγ interactions is that vacuum features magnetic birefringence as a macroscopic property. Magnetic Birefringence of Vacuum (MBV) is due to interactions of beam photons with virtual photons of a magnetic field. These interactions are mediated by loops of electron-positron and (with extremely weaker effects) by loops of muons and loops of hadrons, and could possibly be mediated by hypothetical very light particles with a coupling to two photons. Experimentation to detect MBV not only has started much later than experiments that have provided magnificent validations of QED, like g-2 and Lamb shift, but has not yet matched the performances necessary to observe MBV. A summary of the main properties and performances of experiments aiming at MBV detection is given with focus on recent results of the PVLAS experiment. The time evolution of the missing factor which monitors the capability of an experiment to observe MBV is reported. This evolution points to MBV detection in a near future. MBV experimentation could evolve from detection to precision measurements modulo a change in scale of the experiments, if it will be possible to exploit together the peak performances achieved separately in components of different MBV experiments. Data collected with the aim of detecting MBV provide at present the best model independent limits on the coupling to two photons of (so far hypothetical) very light scalar and pseudoscalar particles
The measurement of a single-mode thermal field with a microwave cavity parametric amplifier
No full textIn this paper, we present the experimental study of a single-mode thermal field carried out using a microwave parametric amplifier tuned at 1.5 GHz and working at room temperature. The parametric amplifier is based on a variable capacitance diode placed inside a microwave resonant cavity. The measured distribution of the thermal photons inside the resonator follows the expected Bose–Einstein distribution probability
Testing the neutrality of matter by acoustic means in a spherical resonator
No full textMeasurements to test the neutrality of matter by acoustic means are reported. The apparatus is based on a spherical capacitor filled with gaseous SF_6 excited by an oscillating electric field. The apparatus has been calibrated measuring the electric polarizability. Assuming charge conservation in the β decay of the neutron, the experiment gives a limit of \epsilon_{p−e} <= 1 × 10−21 for the electron-proton charge difference, the same limit holding for the charge of the neutron. Previous measurements are critically reviewed and found to be inaccurate
Measuring the magnetic birefringence of vacuum: the PVLAS experiment
No full textWe describe the principle and the status of the PVLAS experiment which is presently running at the INFN section of Ferrara, Italy, to detect the magnetic birefringence of vacuum. This is related to the QED vacuum structure and can be detected by measuring the ellipticity acquired by a linearly polarized light beam propagating through a strong magnetic field. Such an effect is predicted by the Euler–Heisenberg Lagrangian. The method is also sensitive to other hypothetical physical effects such as axion-like particles and in general to any fermion/boson millicharged particle. Here we report on the construction of our apparatus based on a high finesse (> 2 · 10^5) Fabry–Perot cavity and two 0.9 m long 2.5 T permanent dipole rotating magnets, and on the measurements performed on a scaled down test setup. With the test setup we have improved by about a factor 2 the limit on the parameter A_e describing nonlinear electrodynamic effects in vacuum: A_e < 2.9 · 10^−21 T^−2 @ 95% C.L
A Re-Entrant MgB2 Cavity for Dynamic Casimir Experiment
No full textThe use of radio frequencies (RF) superconducting re-entrant cavities has been suggested in the framework of some research to detect photon generation from the vacuum, due to the dynamical Casimir effect. A thin semiconducting slab, put inside the cavity, will be excited by a train of laser pulses of a frequency twice the resonant frequency of the cavity, so that a periodic modu- lation of the dielectric constant of the slab will be realized. In order to produce a RF cavity that can safely work at temperatures larger than 4 K, we have designed and constructed a MgB re-entrant cavity having a resonant frequency in the range of 2–3 GHz. The cavity is made by a cylindrical cup of about 40 mm of internal di- ameter and 40 mm of height and on its base is standing a cylindrical coaxial nose on which the semiconductor slab will be deposited. The details of the construction of the MgB cavity will be presented as well as the measurements of its quality factor, as a function of the temperature
On measuring birefringences and dichroisms using Fabry–Perot cavities
No full textWhen measuring very small ellipticities or rotations induced on a polarized beam of light, Fabry–Pérot cavities are often used to increase the number of passes within the region of interest. In this paper we show that due to the intrinsic birefringence of the reflective surface of the cavity mirrors, a cross talk between dichroism and ellipticity is induced. We also show how such a cross talk may be measured and kept under control by means of an adequate phase locking scheme of the laser to the cavity
Direct excitation of the magnetisation in photon-magnon hybrid systems with an infrared laser pulse
No full textWe present experimental results concerning the direct excitation of the magnetisation in a photon-magnon hybrid system composed of a microwave cavity and an embedded yttrium iron garnet (YIG) sphere. An 11 ps ultrafast pulsed laser, with wavelength of 1064 nm outside the YIG transparence window, directly excite the magnon modes. We measure the energy deposited in the Kittel mode of magnetisation by exploiting its coupling to the TE102 mode of the rectangular microwave cavity in the strong coupling regime. Energy collection is performed by a standard rf detection chain reading an antenna matched to the cavity resonance. This technique can prove to be essential in the study of the dynamics of cavity magnon-polaritons, finding application in dark matter axion searches and future magnon based quantum information studies
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