This paper reports the development of a sensor based on surface-enhanced Raman scattering (SERS) for analyses in seawater.
Polycyclic aromatic hydrocarbons (PAHs) are targeted by these sensors and their detection in situ summons up
chemical synthesis and optical development. Firstly, a relevant synthesis of SERS active substrates based on gold
nanostructures is presented. Different kinds of substrates have been synthesized under variable experimental conditions
to modify some parameters such as i) gold shape, size and distribution and such as ii) chemical functionalization: (i) gold
nanoparticles were prepared either by chemical reduction of HAuCl<sub>4</sub> or by physical deposition. (ii) Substrates were
functionalized by hydrophobic films to allow nonpolar molecules pre-concentration. Low concentration from ppb to ppm
of PAHs were detected with a Raman microscope designed for lab experiments. Sensors exhibit strong enhancement of
Raman scattering from molecules adsorbed on the films. Spectra were recorded for two PAHs (naphthalene and pyrene)
in artificial sea-water with limits of detection of 10ppb for both with a short integration time (10s) and a low incident
laser power (~0.1mW). Active substrate surface morphology was characterized with scanning electron microscopy
(SEM) measurements. Secondly, an home-made in situ Raman spectrometer was developed and has been connected to a
micro-fluidic system. This system was designed to host SERS-active sensors in order to ensure measurements with a
flow cell. This original configuration of in situ Raman spectroscopy was then achieved. Such a device is now ready to
use to confirm the PAH detection at ppb levels during the offshore experiments thanks to SERS sensors.
This paper reports an accurate design of Er<sup>3+</sup>-Yb<sup>3+</sup>-Ce<sup>3+</sup> doped ZrF<sub>4</sub>-ErF<sub>3</sub>-LaF<sub>3</sub>-AlF<sub>3</sub> (ZELA) fluoride glass channel
amplifier operating in the third window of the telecommunication systems. By considering measured spectroscopic and
optical parameters, we demonstrate the feasibility of a novel optical waveguide amplifier exhibiting high gain and low
noise figure. The electromagnetic investigation has been carried-out by employing a full-vector Finite Element Method
(FEM) solver. The mode electromagnetic field, calculated at different wavelengths, constitutes the input data for the
home-made numerical code which solves both the power propagation and population rate equations via a Runge-Kutta
based iterative algorithm. The dependence of the up-conversion coefficients on erbium concentration are taken into
account. In the simulations, the core shape, the waveguide length, the input pump and signal powers, the erbium and the
ytterbium concentration are varied with the aim to optimize the amplifier performance. The goal of achieving high gain
with a short device length is demonstrated. In particular, the simulation results show that the waveguide amplifier
exhibits an optimal internal gain value close to 22.5 dB and a noise figure of 4.1 dB for a waveguide amplifier 5.5 cm
long, an erbium concentration of N<sub>Er</sub>=2.5×10<sup>26</sup> ions/m<sup>3</sup>, ytterbium concentration N<sub>Yb</sub>=2.4×10<sup>26</sup> ions/m<sup>3</sup>, N<sub>Ce</sub>=6×10<sup>26</sup>
ions/m<sup>3</sup>, an input pump power P<sub>p</sub>=100 mW and an input signal power P<sub>s</sub>=1 μW.
Silica-hafnia glass-ceramics waveguides activated by Er<sup>3+</sup> ions were fabricated by the bottom up technique. Hafnia
nanocrystals were first prepared by colloidal route and then mixed in a silica-hafnia:Er<sup>3+</sup> sol. The resulting sol was
deposited by dip coating on a silica substrate. Optical spectroscopy showed that after incorporation of the nanocrystal in
a glassy waveguide and an adapted heat treatment, erbium ions tends to migrate toward hafnia nanocrystals. Analysis of
the luminescence properties has demonstrated that erbium ions are, at least partially, trapped in a crystalline phase.
Losses measurements at different wavelengths highlight a very low attenuation coefficient indicating that this
nanostructured material is suitable for a single band waveguide amplifier in the C band of telecommunication.
This paper presents the first optical and spectroscopic characterization of zirconium based fluoride planar waveguides
ZE (ZrF<sub>4</sub>-ErF<sub>3</sub>) and ZLE (ZrF<sub>4</sub>-LaF<sub>3</sub>-ErF<sub>3</sub>) that have been fabricated by Physical Vapor Deposition (PVD) in dual evaporation configuration . Transparent thin films have been obtained by adjusting vaporization temperature, composition of the ZrF<sub>4</sub>-based glass and the LaF<sub>3</sub>-ErF<sub>3</sub> batch. In order to improve resistance to moisture, a low refractive index (~1.32) KAlF<sub>4</sub> cladding has also been deposited. Infrared spectrum of the waveguides has confirmed the protecting role of the cladding layer for the active layer regarding hydrolysis. Luminescence measurements on waveguide samples have shown promising properties compared with the bulk samples, indicating that this system may be suitable for ceramization like in bulk configuration [2-3].