F. Perrone

Experimental method to detect the magnetic birefringence of vacuum

We describe the principle and the status of the PVLAS experiment which is being assembled at INFN Laboratori Nazionali di Legnaro (Legnaro, Padua, Italy) to look for coherent effects, related to the QED vacuum structure, on the propagation of a polarized light beam in a strong magnetic field.

Frequency locking of a Nd:YAG laser using the laser itself as the optical phase modulator

We report frequency locking of a Nd:YAG tunable laser to a 2000 finesse 87‐cm‐long Fabry–Perot cavity in air using the Pound–Drever technique. The novelty is that the necessary phase modulation of the beam is obtained using the laser directly instead of an external phase modulator (Pockels cell). The spurious relative amplitude modulation using this method was ∼3×10−5 with a modulation index β∼1 and the spectral density of the frequency difference between the laser and the cavity is below 1 mHz/√Hz in the region 1–500 Hz.

The measurement of vacuum polarization: The PVLAS experiment

The following is a status report of the experiment PVLAS, whose aim is the measurement of the Polarization of Vacuum, induced by a high magnetic field. It includes a detailed description of the experimental set-up, in which a superconducting dipole magnet of more than 8 T, and a Fabry-Perot optical interferometer with a finesse of more than 130,000 are used. The experiment is in progress at the Laboratori Nazionali di Legnaro in Italy.

PVLAS: Vacuum Birefringence And Production And Detection Of Nearly Massless, Weakly Coupled Particles By Optical Techniques

Abstract Nearly massless particles coupling weakly to two photons constitute suitable candidates as dark matter components: experimental searches investigating this effect by optical techniques have recently been conducted. PVLAS is an experiment designed to measure the vacuum magnetic birefringence and to improve the detection sensitivity for the above particles. It is based on a very sensitive ellipsometer and a 9 T superconducting dipole magnet especially developed for this purpose. With a sensitivity of about 10−8 rad/√Hz and an integration time of 106 s we plan to be able to detect a dichroism corresponding to the production of particles with a coupling constant to two photons of 10-8 GeV-1, provided that particles masses are less than 10−3 eV. With our experimental parameters, the vacuum birefringence effect would give to an ellipticity of 10−11 rad

Very high Q frequency‐locked Fabry–Perot cavity

We report measurements on a 1.75 m long Fabry–Perot cavity locked to a Nd:YAG tunable laser using the Pound–Drever technique. The cavity decay time was measured to be about 291 μs corresponding to a quality factor Q of about 5×1011, the highest value ever reported for an optical resonant cavity.

Testing Quantum Electrodynamics: vacuum polarizability and Casimir forces

Besides ruling the dynamics of electric charged particles and photons in the microscopic domain, quantization of the electromagnetic field gives also rise to macroscopic observable effects. We report on the status of two experiments we are carrying out at the INFN Legnaro Laboratories on macroscopic phenomena of the vacuum of quantum electrodynamics, the birefringence induced by a magnetic field and the Casimir forces.

Measurement of the Kerr constant for H2 and D2 gases

The Kerr electro‐optic constant of deuterium and hydrogen gases have been measured at room temperature and atmospheric pressure for λ=632.8 nm, by using a very sensitive ellipsometrycal technique. A significant difference between the Kerr constants of the two gases has been found.