Densification involved in the UV-based photosensitivity of silicaglasses and optical fibers

A comprehensive survey of photosensitivity in silica glasses and optical fiber is reviewed. Recent work on understanding the mechanisms contributing to germanium or aluminum doped fiber photosensitivity is discussed within the framework of photoelastic densification models     

Phase-sensitive optical low-coherence reflectometry technique applied to the characterization of photonic crystal fiber properties

Localized measurements of group-velocity dispersion and birefringence of photonic crystal fibers are achieved with a phase-sensitive optical low-coherence reflectometry technique. This technique is efficient for fiber samples no longer than 1 m. Theoretical simulations are in good agreement with experimental results. As a result, the stress-induced birefringence proves to be at most 1 order of magnitude below the geometrical-shape birefringence.     

Birefringence effect of optical fiber laser with intracore fiberBragg grating

The spectra of Nd³⁺- and Pr³⁺-doped fibre lasers utilizing an intracore Bragg grating reflector written at 1.08-μm Bragg wavelength and a dichroic mirror for cavity feedback have been investigated under 0.6-GHz resolution. Two oscillating frequencies corresponding to two orthogonal linear polarization states of laser emission were observed. The frequencies and orientations of the two linearly polarized emissions could be changed by varying the fiber birefringence with an inline polarization controller. A phenomenological model is proposed to explain the experimental results     

Behavior of Bragg gratings, written in germanosilicate fibers,against γ-ray exposure at low dose rate

Bragg gratings have been written within four germanosilicate fibers either by a pulsed or by a continuous-wave exposure of each fiber to a coherent UV two-beam interference pattern. These gratings have been exposed under steady state conditions to γ-ray doses as high as 10 ⁴ Grays. The dose rates ranged between 10 Gy/h and 1.3×10² Gy/h. The transmission spectra of the fibers have been recorded during and after the ⁶⁰Co irradiation, near the grating Bragg wavelengths. Whereas the induced loss reached 600 dB/km near 1.3 μm, no significant change in the spectral characteristics of the gratings could be detected within the experimental accuracy, enabling their future use in a nuclear environment     

The problem of arsenic interference in the analysis of Cd to evaluate its extractability in soils contaminated by arsenic

The arsenic (As) spectral interference observed in the determination of cadmium (Cd) by inductively coupled plasma atomic emission spectrometry (ICP-AES) was studied in atomic absorption spectrometry (AAS) using flame (FAAS) and graphite furnace (GFAAS) as atomizers. The soils of 15 kitchen gardens located near two smelters in the North of France were selected according the ratio As/Cd. Four different extracting solutions usually used to evaluate the mobility of Cd were chosen to extract Cd from these soil samples: citric acid 0.11 M, acetic acid 0.11 M, calcium chloride 0.01 M and water. The quantitative determinations of Cd in the 15 soils for each solvent were investigated by ICP-AES at two lines (228.802 and 214.438 nm) and by FAAS or GFAAS with two-way background compensation. Compared to the Cd concentrations measured in the acid solutions and in the CaCl₂ solution after the addition of a chemical modifier, it was clearly demonstrated that the high-speed self-reversal background compensation (HSSR-method) was the method of choice to eliminate the spectral interference of As during Cd determination by FAAS and by GFAAS. In water, it was shown that the deuterium lamp used for the background compensation (D₂-method) was able to eliminate the most of the As interference. In comparison with Cd concentrations in water after adding a chemical modifier, those obtained with the HSSR-method were similar and a very good correlation was obtained between these two methods (R² = 0.995). It was therefore established that the HSSR-method would be able to replace the chemical modifiers to eliminate As interference in the determination of Cd-extractable from As contaminated soils.     

Infrared and chemometrics study of the interaction between heavy metals and organic matter in soils

The study of the behavior of heavy metals in soils requires the knowledge of the complexation between soil constituents and metals and this information is not available from conventional analytical techniques such as atomic absorption. Since metals do not absorb mid infrared radiation, we wanted to characterize them using their interaction with the organic matter of soils. The use of chemometrics treatment of the spectroscopic data has demonstrated firstly that the interaction between soil constituents and metals takes place preferentially via organic matter, secondly the high difference between the complexation of lead and zinc into organic matter should be noted. The study of the infrared spectra shows that two bands at 1670-1690 and 1710 cm(-1) vary according to the concentration of lead, which seems to be preferentially complexed by the salicylate functionality.     

Laser spectroscopy of CuS: Analysis of the A2Σ-X2Πi system

Laser excitation spectra of the A²Σ-X²Π_i system have been recorded for ⁶³CuS and ⁶⁵CuS isotopic molecules with a single-mode dye laser operating in the region 17000–18000 cm^?1. For highly overlapped sequences, use of a monochromator as a narrow band filter was necessary to allow rotational analysis. A simultaneous fit of all eight analyzed bands has led to the following spectroscopic constants for ⁶³CuS (in cm^?1):

     

9.

Fictive-Temperature Mapping in Highly Ge-Doped Multimode Optical Fibers     

Lancry  M. Flammer  I. Depecker  C. Poumellec  B. Simons  D. Nouchi  P. Douay  M. 《Lightwave Technology, Journal of》2007,25(5):1198-1205

In this paper, a Fourier transform infrared focal-plane-array detector was used to image the "bond-stretching" vibration mode observed near sigma=1120 cm^-1 of highly Ge-doped graded-index multimode optical fibers (GI-MMFs). We show that the distribution of the peak wavenumber sigma is nonuniform across the core and cladding of the MMF, i.e., sigma is smaller in the core due to the Ge-doping. Next, as calibration curves between sigma and the fictive temperature T_f are not available in the literature for highly Ge-doped glasses (above 7w%), we have determined calibration curves from 1w% to 30w% in Ge. Then, we have applied these corrections in order to estimate, for the first time to our knowledge, the fictive-temperature distribution within multimode-fiber cross section. Using these curves, we show that T_f is higher at the fiber edges, presumably due to faster cooling. Furthermore, there is also a T_f increase in the center of the core (i.e., higher Ge content)     

10.

Progress in solid core photonic bandgap fibers     

Geraud Bouwmans  Vincent Pureur  Aurelie Betourne  Yves Quiquempois  Mathias Perrin  Laurent Bigot  Marc Douay 《Optical and Quantum Electronics》2007,39(12-13):949-961

We investigate both experimentally and numerically confinement and bend losses in solid-core photonic bandgap fibers. We proposed two designs, based on the addition of air regions in the cladding, allowing these losses to be reduced significantly while keeping the optical properties of bandgap fibers. We also present and discuss numerical results on the impact of transversal defects on the fiber confinement loss in the case of a realistic low loss fiber.     

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State	$\text{v}$	$\text{T}{}_{\mathrm{v}}$	$\text{B}{}_{\mathrm{v}}$	$\text{D}{}_{\mathrm{v}}\text{× 10}{}^6$	$\text{γ}{}_{\mathrm{v}}$	$\text{p}{}_{\mathrm{v}}$	$\text{a}{}_{\mathrm{v}}\text{× 10}{}^6$
$\text{A}{}^2\text{Σ}{}^{\mathrm{?}}$	0	17924.335 (7)	0.17989 (4)	0.177 (7)	0.03853 (7)
$\text{X}{}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$	1	842.574 (7)	0.18701 (4)	0.163 (7)		0.01496 (9)
	0	432.566 (6)	0.18818 (4)	0.162 (7)		0.01508 (9)
$\text{X}{}^2\text{Π}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$	1	411.289 (7)	0.18724 (4)	0.184 (7)			?0.96 (6)
	0	—	0.18839 (4)	0.160 (7)			?0.11 (6)

Fictive-Temperature Mapping in Highly Ge-Doped Multimode Optical Fibers

In this paper, a Fourier transform infrared focal-plane-array detector was used to image the "bond-stretching" vibration mode observed near sigma=1120 cm^-1 of highly Ge-doped graded-index multimode optical fibers (GI-MMFs). We show that the distribution of the peak wavenumber sigma is nonuniform across the core and cladding of the MMF, i.e., sigma is smaller in the core due to the Ge-doping. Next, as calibration curves between sigma and the fictive temperature T_f are not available in the literature for highly Ge-doped glasses (above 7w%), we have determined calibration curves from 1w% to 30w% in Ge. Then, we have applied these corrections in order to estimate, for the first time to our knowledge, the fictive-temperature distribution within multimode-fiber cross section. Using these curves, we show that T_f is higher at the fiber edges, presumably due to faster cooling. Furthermore, there is also a T_f increase in the center of the core (i.e., higher Ge content)     

Progress in solid core photonic bandgap fibers

We investigate both experimentally and numerically confinement and bend losses in solid-core photonic bandgap fibers. We proposed two designs, based on the addition of air regions in the cladding, allowing these losses to be reduced significantly while keeping the optical properties of bandgap fibers. We also present and discuss numerical results on the impact of transversal defects on the fiber confinement loss in the case of a realistic low loss fiber.