The Experts below are selected from a list of 3555 Experts worldwide ranked by ideXlab platform
G Ruoso - One of the best experts on this subject based on the ideXlab platform.
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The PVLAS experiment: a 25 year effort to measure vacuum Magnetic Birefringence.
arXiv: Optics, 2020Co-Authors: A. Ejlli, G Ruoso, F Della Valle, U. Gastaldi, R Pengo, G. Messineo, Guido ZavattiniAbstract:This paper describes the 25 year effort to measure vacuum Magnetic Birefringence and dichroism with the PVLAS experiment. The experiment went through two main phases: the first using a rotating superconducting magnet and the second using two rotating permanent magnets. The experiment was not able to reach the predicted value from QED. Nonetheless the experiment set the current best limits on vacuum Magnetic Birefringence and dichroism for a field of $B_{\rm ext} = 2.5$ T, namely, $\Delta n^{\rm (PVLAS)} = (12\pm17)\times10^{-23}$ and $|\Delta\kappa|^{\rm (PVLAS)} = (10\pm28)\times10^{-23}$. The uncertainty on $\Delta n^{\rm (PVLAS)}$ is about a factor 7 above the predicted value of $\Delta n^{\rm (QED)} = 2.5\times10^{-23}$ @ 2.5 T.
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Intrinsic mirror noise in Fabry-Perot based polarimeters: the case for the measurement of vacuum Magnetic Birefringence
The European Physical Journal C, 2018Co-Authors: Guido Zavattini, A. Ejlli, E Milotti, R Pengo, Ugo Gastaldi, F. Della Valle, G RuosoAbstract:Although experimental efforts have been active for about 30 years now, a direct laboratory observation of vacuum Magnetic Birefringence, an effect due to vacuum fluctuations, still needs confirmation. Indeed, the predicted Birefringence of vacuum is $\Delta n = 4.0\times 10^{-24}$ @ 1~T. One of the key ingredients when designing a polarimeter capable of detecting such a small Birefringence is a long optical path length within the Magnetic field and a time dependent effect. To lengthen the optical path within the Magnetic field a Fabry-Perot optical cavity is generally used with a finesse ranging from ${\cal F} \approx 10^4$ to ${\cal F} \approx7\times 10^5$. Interestingly, there is a difficulty in reaching the predicted shot noise limit of such polarimeters. We have measured the ellipticity and rotation noises along with a Cotton-Mouton and a Faraday effect as a function of the finesse of the cavity of the PVLAS polarimeter. The observations are consistent with the idea that the cavity mirrors generate a Birefringence-dominated noise whose ellipticity is amplified by the cavity itself. The optical path difference sensitivity at $10\;$Hz is $S_{\Delta{\cal D}}=6\times 10^{-19}\;$m$/\sqrt{\rm Hz}$, a value which we believe is consistent with an intrinsic thermal noise in the mirror coatings.
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Intrinsic mirror noise in Fabry–Perot based polarimeters: the case for the measurement of vacuum Magnetic Birefringence
The European Physical Journal C, 2018Co-Authors: Guido Zavattini, A. Ejlli, E Milotti, U. Gastaldi, R Pengo, F. Della Valle, G RuosoAbstract:Although experimental efforts have been active for about 30 years, a direct laboratory observation of vacuum Magnetic Birefringence, due to vacuum fluctuations, still needs confirmation: the predicted Birefringence of vacuum is $$\Delta n = 4.0\times 10^{-24}$$ Δ n = 4.0 × 10 - 24 @ 1 T. Key ingredients of a polarimeter for detecting such a small Birefringence are a long optical path within the Magnetic field and a time dependent effect. To lengthen the optical path a Fabry–Perot is generally used with a finesse ranging from $${{\mathscr {F}}} \approx 10^4$$ F ≈ 10 4 to $${{\mathscr {F}}} \approx 7\times 10^5$$ F ≈ 7 × 10 5 . Interestingly, there is a difficulty in reaching the predicted shot noise limit of such polarimeters. We have measured the ellipticity and rotation noises along with Cotton-Mouton and Faraday effects as a function of the finesse of the cavity of the PVLAS polarimeter. The observations are consistent with the idea that the cavity mirrors generate a Birefringence-dominated noise whose ellipticity is amplified by the cavity itself. The optical path difference sensitivity at $$10\;\hbox {Hz}$$ 10 Hz is $$S_{\Delta {{\mathscr {D}}}}=6\times 10^{-19}\;\hbox {m}/\sqrt{\mathrm{Hz}}$$ S Δ D = 6 × 10 - 19 m / Hz , a value which we believe is consistent with an intrinsic thermal noise in the mirror coatings. Our findings prove that the continuous efforts to increase the finesse of the cavity to improve the sensitivity has reached a limit.
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intrinsic mirror noise in fabry perot based polarimeters the case for the measurement of vacuum Magnetic Birefringence
European Physical Journal C, 2018Co-Authors: Guido Zavattini, A. Ejlli, Ni W T, F Della Valle, E Milotti, U. Gastaldi, R Pengo, G RuosoAbstract:Although experimental efforts have been active for about 30 years, a direct laboratory observation of vacuum Magnetic Birefringence, due to vacuum fluctuations, still needs confirmation: the predicted Birefringence of vacuum is \(\Delta n = 4.0\times 10^{-24}\) @ 1 T. Key ingredients of a polarimeter for detecting such a small Birefringence are a long optical path within the Magnetic field and a time dependent effect. To lengthen the optical path a Fabry–Perot is generally used with a finesse ranging from \({{\mathscr {F}}} \approx 10^4\) to \({{\mathscr {F}}} \approx 7\times 10^5\). Interestingly, there is a difficulty in reaching the predicted shot noise limit of such polarimeters. We have measured the ellipticity and rotation noises along with Cotton-Mouton and Faraday effects as a function of the finesse of the cavity of the PVLAS polarimeter. The observations are consistent with the idea that the cavity mirrors generate a Birefringence-dominated noise whose ellipticity is amplified by the cavity itself. The optical path difference sensitivity at \(10\;\hbox {Hz}\) is \(S_{\Delta {{\mathscr {D}}}}=6\times 10^{-19}\;\hbox {m}/\sqrt{\mathrm{Hz}}\), a value which we believe is consistent with an intrinsic thermal noise in the mirror coatings. Our findings prove that the continuous efforts to increase the finesse of the cavity to improve the sensitivity has reached a limit.
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A polarisation modulation scheme for measuring vacuum Magnetic Birefringence with static fields
The European Physical Journal C, 2016Co-Authors: Guido Zavattini, A. Ejlli, F. Della valle, G RuosoAbstract:A novel polarisation modulation scheme for polarimeters based on Fabry–Perot cavities is presented. The application to the measurement of the Magnetic Birefringence of vacuum with the HERA superconducting magnets in the ALPS-II configuration is discussed.
Guido Zavattini - One of the best experts on this subject based on the ideXlab platform.
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The PVLAS experiment: a 25 year effort to measure vacuum Magnetic Birefringence.
arXiv: Optics, 2020Co-Authors: A. Ejlli, G Ruoso, F Della Valle, U. Gastaldi, R Pengo, G. Messineo, Guido ZavattiniAbstract:This paper describes the 25 year effort to measure vacuum Magnetic Birefringence and dichroism with the PVLAS experiment. The experiment went through two main phases: the first using a rotating superconducting magnet and the second using two rotating permanent magnets. The experiment was not able to reach the predicted value from QED. Nonetheless the experiment set the current best limits on vacuum Magnetic Birefringence and dichroism for a field of $B_{\rm ext} = 2.5$ T, namely, $\Delta n^{\rm (PVLAS)} = (12\pm17)\times10^{-23}$ and $|\Delta\kappa|^{\rm (PVLAS)} = (10\pm28)\times10^{-23}$. The uncertainty on $\Delta n^{\rm (PVLAS)}$ is about a factor 7 above the predicted value of $\Delta n^{\rm (QED)} = 2.5\times10^{-23}$ @ 2.5 T.
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Intrinsic mirror noise in Fabry-Perot based polarimeters: the case for the measurement of vacuum Magnetic Birefringence
The European Physical Journal C, 2018Co-Authors: Guido Zavattini, A. Ejlli, E Milotti, R Pengo, Ugo Gastaldi, F. Della Valle, G RuosoAbstract:Although experimental efforts have been active for about 30 years now, a direct laboratory observation of vacuum Magnetic Birefringence, an effect due to vacuum fluctuations, still needs confirmation. Indeed, the predicted Birefringence of vacuum is $\Delta n = 4.0\times 10^{-24}$ @ 1~T. One of the key ingredients when designing a polarimeter capable of detecting such a small Birefringence is a long optical path length within the Magnetic field and a time dependent effect. To lengthen the optical path within the Magnetic field a Fabry-Perot optical cavity is generally used with a finesse ranging from ${\cal F} \approx 10^4$ to ${\cal F} \approx7\times 10^5$. Interestingly, there is a difficulty in reaching the predicted shot noise limit of such polarimeters. We have measured the ellipticity and rotation noises along with a Cotton-Mouton and a Faraday effect as a function of the finesse of the cavity of the PVLAS polarimeter. The observations are consistent with the idea that the cavity mirrors generate a Birefringence-dominated noise whose ellipticity is amplified by the cavity itself. The optical path difference sensitivity at $10\;$Hz is $S_{\Delta{\cal D}}=6\times 10^{-19}\;$m$/\sqrt{\rm Hz}$, a value which we believe is consistent with an intrinsic thermal noise in the mirror coatings.
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Intrinsic mirror noise in Fabry–Perot based polarimeters: the case for the measurement of vacuum Magnetic Birefringence
The European Physical Journal C, 2018Co-Authors: Guido Zavattini, A. Ejlli, E Milotti, U. Gastaldi, R Pengo, F. Della Valle, G RuosoAbstract:Although experimental efforts have been active for about 30 years, a direct laboratory observation of vacuum Magnetic Birefringence, due to vacuum fluctuations, still needs confirmation: the predicted Birefringence of vacuum is $$\Delta n = 4.0\times 10^{-24}$$ Δ n = 4.0 × 10 - 24 @ 1 T. Key ingredients of a polarimeter for detecting such a small Birefringence are a long optical path within the Magnetic field and a time dependent effect. To lengthen the optical path a Fabry–Perot is generally used with a finesse ranging from $${{\mathscr {F}}} \approx 10^4$$ F ≈ 10 4 to $${{\mathscr {F}}} \approx 7\times 10^5$$ F ≈ 7 × 10 5 . Interestingly, there is a difficulty in reaching the predicted shot noise limit of such polarimeters. We have measured the ellipticity and rotation noises along with Cotton-Mouton and Faraday effects as a function of the finesse of the cavity of the PVLAS polarimeter. The observations are consistent with the idea that the cavity mirrors generate a Birefringence-dominated noise whose ellipticity is amplified by the cavity itself. The optical path difference sensitivity at $$10\;\hbox {Hz}$$ 10 Hz is $$S_{\Delta {{\mathscr {D}}}}=6\times 10^{-19}\;\hbox {m}/\sqrt{\mathrm{Hz}}$$ S Δ D = 6 × 10 - 19 m / Hz , a value which we believe is consistent with an intrinsic thermal noise in the mirror coatings. Our findings prove that the continuous efforts to increase the finesse of the cavity to improve the sensitivity has reached a limit.
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intrinsic mirror noise in fabry perot based polarimeters the case for the measurement of vacuum Magnetic Birefringence
European Physical Journal C, 2018Co-Authors: Guido Zavattini, A. Ejlli, Ni W T, F Della Valle, E Milotti, U. Gastaldi, R Pengo, G RuosoAbstract:Although experimental efforts have been active for about 30 years, a direct laboratory observation of vacuum Magnetic Birefringence, due to vacuum fluctuations, still needs confirmation: the predicted Birefringence of vacuum is \(\Delta n = 4.0\times 10^{-24}\) @ 1 T. Key ingredients of a polarimeter for detecting such a small Birefringence are a long optical path within the Magnetic field and a time dependent effect. To lengthen the optical path a Fabry–Perot is generally used with a finesse ranging from \({{\mathscr {F}}} \approx 10^4\) to \({{\mathscr {F}}} \approx 7\times 10^5\). Interestingly, there is a difficulty in reaching the predicted shot noise limit of such polarimeters. We have measured the ellipticity and rotation noises along with Cotton-Mouton and Faraday effects as a function of the finesse of the cavity of the PVLAS polarimeter. The observations are consistent with the idea that the cavity mirrors generate a Birefringence-dominated noise whose ellipticity is amplified by the cavity itself. The optical path difference sensitivity at \(10\;\hbox {Hz}\) is \(S_{\Delta {{\mathscr {D}}}}=6\times 10^{-19}\;\hbox {m}/\sqrt{\mathrm{Hz}}\), a value which we believe is consistent with an intrinsic thermal noise in the mirror coatings. Our findings prove that the continuous efforts to increase the finesse of the cavity to improve the sensitivity has reached a limit.
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A polarisation modulation scheme for measuring vacuum Magnetic Birefringence with static fields
The European Physical Journal C, 2016Co-Authors: Guido Zavattini, A. Ejlli, F. Della valle, G RuosoAbstract:A novel polarisation modulation scheme for polarimeters based on Fabry–Perot cavities is presented. The application to the measurement of the Magnetic Birefringence of vacuum with the HERA superconducting magnets in the ALPS-II configuration is discussed.
Jose M. Colino - One of the best experts on this subject based on the ideXlab platform.
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form and Magnetic Birefringence in undulated permalloy pet films
Optics Express, 2019Co-Authors: M A Arranz, Elena H. Sánchez, Esther Rebollar, Marta Castillejo, Jose M. ColinoAbstract:We report the measurement of form and Magnetic Birefringence in Permalloy (Ni80Fe20) films grown on rippled Poly(Ethylene Terephthalate), PET, substrates. Prior to Permalloy deposition, Laser Induced Periodic Surface Structures (LIPSS) were generated on the polymeric substrate by a nanosecond laser beam, developing an ordered rippled nanostructure. Due to their high transparency factor, we could investigate the behavior of linear polarized light transmitting at normal incidence on Permalloy/PET sample. The results show the existence of an optical axis parallel to the ripples direction, which yields an strong form Birefringence effect arising from the laser patterning. Concerning the Permalloy thin film, the study of its in-plane magnetization was carried out measuring the Voigt magnetooptical effect. The obtained data in our samples reveal the appearance of two different mechanisms to reverse the magnetization, as the external Magnetic field is parallel or perpendicular to the ripples direction. Accordingly, the transmitted light shows a Magnetic Birefringence depending on the relative orientation between the ripple direction, i.e. the optical axis of the LIPSS, and the in-plane magnetization of the Permalloy film.
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Form and Magnetic Birefringence in undulated Permalloy/PET films
Optics express, 2019Co-Authors: M A Arranz, Elena H. Sánchez, Esther Rebollar, Marta Castillejo, Jose M. ColinoAbstract:We report the measurement of form and Magnetic Birefringence in Permalloy (Ni80Fe20) films grown on rippled Poly(Ethylene Terephthalate), PET, substrates. Prior to Permalloy deposition, Laser Induced Periodic Surface Structures (LIPSS) were generated on the polymeric substrate by a nanosecond laser beam, developing an ordered rippled nanostructure. Due to their high transparency factor, we could investigate the behavior of linear polarized light transmitting at normal incidence on Permalloy/PET sample. The results show the existence of an optical axis parallel to the ripples direction, which yields an strong form Birefringence effect arising from the laser patterning. Concerning the Permalloy thin film, the study of its in-plane magnetization was carried out measuring the Voigt magnetooptical effect. The obtained data in our samples reveal the appearance of two different mechanisms to reverse the magnetization, as the external Magnetic field is parallel or perpendicular to the ripples direction. Accordingly, the transmitted light shows a Magnetic Birefringence depending on the relative orientation between the ripple direction, i.e. the optical axis of the LIPSS, and the in-plane magnetization of the Permalloy film.
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Angular tuning of the Magnetic Birefringence in rippled cobalt films
Applied Physics Letters, 2015Co-Authors: M A Arranz, Jose M. ColinoAbstract:We report the measurement of Magnetically induced Birefringence in rippled Co films. For this purpose, the magneto-optical properties of ion beam eroded ferroMagnetic films were studied using Kerr magnetometry and Magnetic Birefringence in the transmitted light intensity. Upon sufficient ion sculpting, these ripple surface nanostructures developed a defined uniaxial anisotropy in the in-plane magnetization, finely tuning the Magnetic Birefringence effect. We have studied its dependence on the relative orientation between the ripple direction and the Magnetic field, and found this effect to be dramatically correlated with the capability to neatly distinguish the mechanisms for the in-plane magnetization reversal, i.e., rotation and nucleation. This double refraction corresponds univocally to the two magnetization axes, parallel and perpendicular to the ripples direction. We have also observed that tuned Birefringence in stack assemblies of rippled Co films, which enables us to technically manipulate the number and direction of refraction axes.
A. Ejlli - One of the best experts on this subject based on the ideXlab platform.
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The PVLAS experiment: a 25 year effort to measure vacuum Magnetic Birefringence.
arXiv: Optics, 2020Co-Authors: A. Ejlli, G Ruoso, F Della Valle, U. Gastaldi, R Pengo, G. Messineo, Guido ZavattiniAbstract:This paper describes the 25 year effort to measure vacuum Magnetic Birefringence and dichroism with the PVLAS experiment. The experiment went through two main phases: the first using a rotating superconducting magnet and the second using two rotating permanent magnets. The experiment was not able to reach the predicted value from QED. Nonetheless the experiment set the current best limits on vacuum Magnetic Birefringence and dichroism for a field of $B_{\rm ext} = 2.5$ T, namely, $\Delta n^{\rm (PVLAS)} = (12\pm17)\times10^{-23}$ and $|\Delta\kappa|^{\rm (PVLAS)} = (10\pm28)\times10^{-23}$. The uncertainty on $\Delta n^{\rm (PVLAS)}$ is about a factor 7 above the predicted value of $\Delta n^{\rm (QED)} = 2.5\times10^{-23}$ @ 2.5 T.
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Intrinsic mirror noise in Fabry-Perot based polarimeters: the case for the measurement of vacuum Magnetic Birefringence
The European Physical Journal C, 2018Co-Authors: Guido Zavattini, A. Ejlli, E Milotti, R Pengo, Ugo Gastaldi, F. Della Valle, G RuosoAbstract:Although experimental efforts have been active for about 30 years now, a direct laboratory observation of vacuum Magnetic Birefringence, an effect due to vacuum fluctuations, still needs confirmation. Indeed, the predicted Birefringence of vacuum is $\Delta n = 4.0\times 10^{-24}$ @ 1~T. One of the key ingredients when designing a polarimeter capable of detecting such a small Birefringence is a long optical path length within the Magnetic field and a time dependent effect. To lengthen the optical path within the Magnetic field a Fabry-Perot optical cavity is generally used with a finesse ranging from ${\cal F} \approx 10^4$ to ${\cal F} \approx7\times 10^5$. Interestingly, there is a difficulty in reaching the predicted shot noise limit of such polarimeters. We have measured the ellipticity and rotation noises along with a Cotton-Mouton and a Faraday effect as a function of the finesse of the cavity of the PVLAS polarimeter. The observations are consistent with the idea that the cavity mirrors generate a Birefringence-dominated noise whose ellipticity is amplified by the cavity itself. The optical path difference sensitivity at $10\;$Hz is $S_{\Delta{\cal D}}=6\times 10^{-19}\;$m$/\sqrt{\rm Hz}$, a value which we believe is consistent with an intrinsic thermal noise in the mirror coatings.
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Intrinsic mirror noise in Fabry–Perot based polarimeters: the case for the measurement of vacuum Magnetic Birefringence
The European Physical Journal C, 2018Co-Authors: Guido Zavattini, A. Ejlli, E Milotti, U. Gastaldi, R Pengo, F. Della Valle, G RuosoAbstract:Although experimental efforts have been active for about 30 years, a direct laboratory observation of vacuum Magnetic Birefringence, due to vacuum fluctuations, still needs confirmation: the predicted Birefringence of vacuum is $$\Delta n = 4.0\times 10^{-24}$$ Δ n = 4.0 × 10 - 24 @ 1 T. Key ingredients of a polarimeter for detecting such a small Birefringence are a long optical path within the Magnetic field and a time dependent effect. To lengthen the optical path a Fabry–Perot is generally used with a finesse ranging from $${{\mathscr {F}}} \approx 10^4$$ F ≈ 10 4 to $${{\mathscr {F}}} \approx 7\times 10^5$$ F ≈ 7 × 10 5 . Interestingly, there is a difficulty in reaching the predicted shot noise limit of such polarimeters. We have measured the ellipticity and rotation noises along with Cotton-Mouton and Faraday effects as a function of the finesse of the cavity of the PVLAS polarimeter. The observations are consistent with the idea that the cavity mirrors generate a Birefringence-dominated noise whose ellipticity is amplified by the cavity itself. The optical path difference sensitivity at $$10\;\hbox {Hz}$$ 10 Hz is $$S_{\Delta {{\mathscr {D}}}}=6\times 10^{-19}\;\hbox {m}/\sqrt{\mathrm{Hz}}$$ S Δ D = 6 × 10 - 19 m / Hz , a value which we believe is consistent with an intrinsic thermal noise in the mirror coatings. Our findings prove that the continuous efforts to increase the finesse of the cavity to improve the sensitivity has reached a limit.
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intrinsic mirror noise in fabry perot based polarimeters the case for the measurement of vacuum Magnetic Birefringence
European Physical Journal C, 2018Co-Authors: Guido Zavattini, A. Ejlli, Ni W T, F Della Valle, E Milotti, U. Gastaldi, R Pengo, G RuosoAbstract:Although experimental efforts have been active for about 30 years, a direct laboratory observation of vacuum Magnetic Birefringence, due to vacuum fluctuations, still needs confirmation: the predicted Birefringence of vacuum is \(\Delta n = 4.0\times 10^{-24}\) @ 1 T. Key ingredients of a polarimeter for detecting such a small Birefringence are a long optical path within the Magnetic field and a time dependent effect. To lengthen the optical path a Fabry–Perot is generally used with a finesse ranging from \({{\mathscr {F}}} \approx 10^4\) to \({{\mathscr {F}}} \approx 7\times 10^5\). Interestingly, there is a difficulty in reaching the predicted shot noise limit of such polarimeters. We have measured the ellipticity and rotation noises along with Cotton-Mouton and Faraday effects as a function of the finesse of the cavity of the PVLAS polarimeter. The observations are consistent with the idea that the cavity mirrors generate a Birefringence-dominated noise whose ellipticity is amplified by the cavity itself. The optical path difference sensitivity at \(10\;\hbox {Hz}\) is \(S_{\Delta {{\mathscr {D}}}}=6\times 10^{-19}\;\hbox {m}/\sqrt{\mathrm{Hz}}\), a value which we believe is consistent with an intrinsic thermal noise in the mirror coatings. Our findings prove that the continuous efforts to increase the finesse of the cavity to improve the sensitivity has reached a limit.
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A polarisation modulation scheme for measuring vacuum Magnetic Birefringence with static fields
The European Physical Journal C, 2016Co-Authors: Guido Zavattini, A. Ejlli, F. Della valle, G RuosoAbstract:A novel polarisation modulation scheme for polarimeters based on Fabry–Perot cavities is presented. The application to the measurement of the Magnetic Birefringence of vacuum with the HERA superconducting magnets in the ALPS-II configuration is discussed.
F Della Valle - One of the best experts on this subject based on the ideXlab platform.
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The PVLAS experiment: a 25 year effort to measure vacuum Magnetic Birefringence.
arXiv: Optics, 2020Co-Authors: A. Ejlli, G Ruoso, F Della Valle, U. Gastaldi, R Pengo, G. Messineo, Guido ZavattiniAbstract:This paper describes the 25 year effort to measure vacuum Magnetic Birefringence and dichroism with the PVLAS experiment. The experiment went through two main phases: the first using a rotating superconducting magnet and the second using two rotating permanent magnets. The experiment was not able to reach the predicted value from QED. Nonetheless the experiment set the current best limits on vacuum Magnetic Birefringence and dichroism for a field of $B_{\rm ext} = 2.5$ T, namely, $\Delta n^{\rm (PVLAS)} = (12\pm17)\times10^{-23}$ and $|\Delta\kappa|^{\rm (PVLAS)} = (10\pm28)\times10^{-23}$. The uncertainty on $\Delta n^{\rm (PVLAS)}$ is about a factor 7 above the predicted value of $\Delta n^{\rm (QED)} = 2.5\times10^{-23}$ @ 2.5 T.
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intrinsic mirror noise in fabry perot based polarimeters the case for the measurement of vacuum Magnetic Birefringence
European Physical Journal C, 2018Co-Authors: Guido Zavattini, A. Ejlli, Ni W T, F Della Valle, E Milotti, U. Gastaldi, R Pengo, G RuosoAbstract:Although experimental efforts have been active for about 30 years, a direct laboratory observation of vacuum Magnetic Birefringence, due to vacuum fluctuations, still needs confirmation: the predicted Birefringence of vacuum is \(\Delta n = 4.0\times 10^{-24}\) @ 1 T. Key ingredients of a polarimeter for detecting such a small Birefringence are a long optical path within the Magnetic field and a time dependent effect. To lengthen the optical path a Fabry–Perot is generally used with a finesse ranging from \({{\mathscr {F}}} \approx 10^4\) to \({{\mathscr {F}}} \approx 7\times 10^5\). Interestingly, there is a difficulty in reaching the predicted shot noise limit of such polarimeters. We have measured the ellipticity and rotation noises along with Cotton-Mouton and Faraday effects as a function of the finesse of the cavity of the PVLAS polarimeter. The observations are consistent with the idea that the cavity mirrors generate a Birefringence-dominated noise whose ellipticity is amplified by the cavity itself. The optical path difference sensitivity at \(10\;\hbox {Hz}\) is \(S_{\Delta {{\mathscr {D}}}}=6\times 10^{-19}\;\hbox {m}/\sqrt{\mathrm{Hz}}\), a value which we believe is consistent with an intrinsic thermal noise in the mirror coatings. Our findings prove that the continuous efforts to increase the finesse of the cavity to improve the sensitivity has reached a limit.
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The PVLAS experiment: measuring vacuum Magnetic Birefringence and dichroism with a birefringent Fabry–Perot cavity
The European Physical Journal C, 2016Co-Authors: F Della Valle, A. Ejlli, G Ruoso, E Milotti, R Pengo, Ugo Gastaldi, Giuseppe Messineo, Guido ZavattiniAbstract:Vacuum Magnetic Birefringence was predicted long time ago and is still lacking a direct experimental confirmation. Several experimental efforts are striving to reach this goal, and the sequence of results promises a success in the next few years. This measurement generally is accompanied by the search for hypothetical light particles that couple to two photons. The PVLAS experiment employs a sensitive polarimeter based on a high finesse Fabry–Perot cavity. In this paper we report on the latest experimental results of this experiment. The data are analysed taking into account the intrinsic Birefringence of the dielectric mirrors of the cavity. Besides a new limit on the vacuum Magnetic Birefringence, the measurements also allow the model-independent exclusion of new regions in the parameter space of axion-like and milli-charged particles. In particular, these last limits hold also for all types of neutrinos, resulting in a laboratory limit on their charge.
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a polarisation modulation scheme for measuring vacuum Magnetic Birefringence with static fields
arXiv: Optics, 2016Co-Authors: Guido Zavattini, A. Ejlli, F Della Valle, G RuosoAbstract:A novel polarisation modulation scheme for polarimeters based on Fabry-Perot cavities is presented. The application to the proposed HERA-X experiment aiming to measuring the Magnetic Birefringence of vacuum with the HERA superconducting magnets is discussed.
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the pvlas experiment measuring vacuum Magnetic Birefringence and dichroism with a birefringent fabry perot cavity
European Physical Journal C, 2016Co-Authors: F Della Valle, A. Ejlli, G Ruoso, E Milotti, U. Gastaldi, R Pengo, G. Messineo, Guido ZavattiniAbstract:Vacuum Magnetic Birefringence was predicted long time ago and is still lacking a direct experimental confirmation. Several experimental efforts are striving to reach this goal, and the sequence of results promises a success in the next few years. This measurement generally is accompanied by the search for hypothetical light particles that couple to two photons. The PVLAS experiment employs a sensitive polarimeter based on a high finesse Fabry–Perot cavity. In this paper we report on the latest experimental results of this experiment. The data are analysed taking into account the intrinsic Birefringence of the dielectric mirrors of the cavity. Besides a new limit on the vacuum Magnetic Birefringence, the measurements also allow the model-independent exclusion of new regions in the parameter space of axion-like and milli-charged particles. In particular, these last limits hold also for all types of neutrinos, resulting in a laboratory limit on their charge.
