Search results for "optics"
showing 10 items of 10033 documents
Higher-order Kerr terms allow ionization-free filamentation in gases
2010
Talk given by J. Kasparian; International audience; Higher-order nonlinear indices, rather than plasma, provide the main defocusing contribution to filamentation in gases at 800 nm. Developing generalized Miller formulae, we discuss the generality of this as a function of the laser wavelength
Radioluminescence Response of Ce-, Cu-, and Gd-Doped Silica Glasses for Dosimetry of Pulsed Electron Beams
2021
Radiation-induced emission of doped sol-gel silica glass samples was investigated under a pulsed 20-MeV electron beam. The studied samples were drawn rods doped with cerium, copper, or gadolinium ions, which were connected to multimode pure-silica core fibers to transport the induced luminescence from the irradiation area to a signal readout system. The luminescence pulses in the samples induced by the electron bunches were studied as a function of deposited dose per electron bunch. All the investigated samples were found to have a linear response in terms of luminescence as a function of electron bunch sizes between 10−5 Gy/bunch and 1.5×10−2 Gy/bunch. The presented results show that these…
O2-Loading Treatment of Ge-Doped Silica Fibers: A Radiation Hardening Process
2016
International audience; The effects of a high-pressure O2-loading treatment on the radiation response of Ge-doped optical fibers (OFs) were investigated. We found that the incorporation of high concentration of interstitial molecular oxygen remarkably enhances the resistance to ionizing radiation of Ge-doped OFs in the UV-Visible domain and, at the same time, improves the transmission of UV light in the unirradiated OF sample. By comparison with previously reported results, the O2-loading treatment turned out to increase the radiation resistance of Ge-doped OFs more efficiently than F or Ce codoping. The understanding of such amelioration relies in basic radiation-induced mechanisms that we…
Radiation Response of Ce-Codoped Germanosilicate and Phosphosilicate Optical Fibers
2016
We report an experimental investigation on the effects of Ce-codoping in determining the radiation response of germanosilicate and phosphosilicate Optical Fibers (OFs) in the UV-Visible domain and up to doses of $1~\hbox{MGy}({\rm SiO}_{2})$ . We show that the addition of Ce strongly impacts the Radiation Induced Attenuation (RIA) of both types of fibers. In the first case the radiation induced losses increase, whereas in the second one decrease. By combining the online RIA measurements with the Electron Paramagnetic Resonance (EPR) ones, we are able to infer the basic microscopic mechanisms taking place under irradiation, which involve the cerium codopant and some of the known Ge-related o…
On-Line Characterization of Gamma Radiation Effects on Single-Ended Raman Based Distributed Fiber Optic Sensor
2016
We report distributed temperature measurements based on Raman scattering performed during steady state $\gamma $ -ray irradiation at a dose rate of 1 kGy( ${\rm SiO}_{2}$ )/h and up to a total ionizing dose (TID) of $\sim 0.1\ \hbox{MGy}$ . We characterize on-line the evolution of the performances of a single-ended Raman distributed temperature sensor (RDTS) during the $\gamma $ -ray exposure of different classes of commercial multimode fibers (MMFs) acting as the sensing element. RDTS is influenced by the radiation-induced attenuation (RIA) phenomena leading to both large errors in the temperature measurements and a diminution of the useful sensing length. The amplitude of the radiation-in…
Temporal spying and concealing process in fibre-optic data transmission systems through polarization bypass
2014
Recent research has been focused on the ability to manipulate a light beam in such a way to hide, namely to cloak, an event over a finite time or localization in space. The main idea is to create a hole or a gap in the spatial or time domain so as to allow for an object or data to be kept hidden for a while and then to be restored. By enlarging the field of applications of this concept to telecommunications, researchers have recently reported the possibility to hide transmitted data in an optical fibre. Here we report the first experimental demonstration of perpetual temporal spying and blinding process of optical data in fibre-optic transmission line based on polarization bypass. We succes…
Investigation of Coating Impact on OFDR Optical Remote Fiber-Based Sensors Performances for Their Integration in High Temperature and Radiation Envir…
2016
The response of optical frequency-domain reflectometry-based temperature sensors is here investigated in harsh environments (high temperature, high radiation dose) focusing the attention on the impact of the fiber coating on the sensor performances in such conditions. Our results demonstrate that the various coating types evolve differently under thermal treatment and/or radiations, resulting in a small (<5%) change in the temperature coefficient of the sensor. The identified procedure, consisting of a prethermal treatment of the fiber at its maximum coating operating temperature, is here verified up to 150 °C for higherature acrylate and up to 300 °C for polyamide coating. This method allo…
Measurement of nonlinear and chromatic dispersion parameters of optical fibers using modulation instability
2006
International audience; We present a simple method for the measurement of Kerr, second- and third-order dispersion coefficients in optical fibers using power and dispersion dependences of modulation instability near the zero-dispersion wavelength. We also complete the analysis by the accurate determination of the zero-dispersion wavelength of the fiber using the phase-matched four wave mixing process which occurs near this specific wavelength.
Efficient interrogation method of forward Brillouin scattering in optical fibers using a narrow bandwidth long-period grating
2020
A new technique, to the best of our knowledge, for the characterization of the effective refractive index modulation in optical fibers due to transverse acoustic mode resonances excited by electrostriction is reported. The resonances excited by an optical pulse are probed by a narrow bandwidth long-period grating (LPG) inscribed in the fiber, which is interrogated by a continuous wave (CW) beam. The LPG used in this experiment has a narrow bandwidth and high sensitivity to small mode index perturbations, allowing the measurement of index variations from below 10 − 9 to 10 − 6 . Radial and torsional-radial acoustic modes were characterized up to 1.1 GHz. The linewidth of resonances was found…
A universal optical all-fiber omnipolarizer
2012
International audience; Wherever the polarization properties of a light beam are of concern, polarizers and polarizing beamsplitters (PBS) are indispensable devices in linear-, nonlinear- and quantum-optical schemes. By the very nature of their operation principle, transformation of incoming unpolarized or partially polarized beams through these devices introduces large intensity variations in the fully polarized outcoming beam(s). Such intensity fluctuations are often detrimental, particularly when light is post-processed by nonlinear crystals or other polarization-sensitive optic elements. Here we demonstrate the unexpected capability of light to self-organize its own state-of-polarizatio…