Powerful 1-µm 1-GHz optical frequency comb.

A self-referenced optical frequency comb is presented based on Kerr-lens mode-locking of ytterbium-doped CALGO. The robust source delivers 3.5 W average power in 44 fs-long pulses at 1 GHz repetition rate.

Design and fabrication of dispersion controlled highly nonlinear fibers for far-detuned four-wave mixing frequency conversion.

We report on the conception, fabrication and characterization of a new concept of optical fiber enabling a precise control of the ratio between the 2 and 4-order of chromatic dispersion (respectively β and β) at 1.55 µm which is at the heart of the Four-Wave-Mixing (FWM) generation. For conventional highly nonlinear fiber the sensitivity of this ratio to fiber geometry fluctuations is very critical, making the fabrication process challenging.

Optimum design of NOLM-driven mode-locked fiber lasers.

Most of the saturable absorbers commonly used to perform mode locking in laser cavities affect the trigger conditions of laser oscillation, which requires manually forcing the laser start-up by various means such as polarization controllers. We present a procedure for designing a laser cavity driven by a nonlinear optical loop mirror, which allows the laser to operate optimally without interfering with the oscillation triggering conditions, thus opening up possibilities for integration of this type of laser.

Highly efficient few-mode spatial beam self-cleaning at 1.5µm.

We experimentally demonstrate that spatial beam self-cleaning can be highly efficient when obtained with a few-mode excitation in graded-index multimode optical fibers. By using 160 ps long, highly chirped (6 nm bandwidth at -3dB) optical pulses at 1562 nm, we demonstrate a one-decade reduction of the power threshold for spatial beam self-cleaning, with respect to previous experiments using pulses with laser wavelengths at 1030-1064 nm. Self-cleaned beams remain spatio-temporally stable for more than a decade of their peak power variation.

Intense stimulated Raman scattering in CO-filled hollow-core fibers.

We demonstrate experimentally, the generation of an intense broadband comb-like spectrum spontaneously built up through stimulated Raman scattering in a low-pressure CO-filled hollow-core photonic crystal fiber pumped by a single infrared pump.

Si-rich Si nitride waveguides for optical transmissions and toward wavelength conversion around 2 μm.

We show that subwavelength Si-rich nitride waveguides efficiently sustain high-speed transmissions at 2 μm. We report the transmission of a 10 Gbit/s signal over 3.5 cm with negligible power penalty.

Electro-optic dual-comb spectrometer in the thulium amplification band for gas sensing applications.

We demonstrate a dual-comb spectrometer based on the direct electro-optic modulation of a continuous-wave laser operating in the thulium amplification band. We show that the emergent two-micrometer technology is already suitable for developing all-fibered dual-comb setups employed here for gas sensing applications. By performing spectroscopic measurements around two micrometers on carbon dioxide, we obtain very good agreement between the experimental results and calculations provided by the HITRAN database.

Spectral broadening of picosecond pulses forming dispersive shock waves in optical fibers.

We investigate analytically, numerically, and experimentally the spectral broadening of pulses that undergo the formation of dispersive shocks, addressing in particular pulses in the range of tens of ps generated via electro-optic modulation of a continuous-wave laser. We give an analytical estimate of the maximal spectral extension and show that super-Gaussian waveforms favor the generation of flat-topped spectra. We also show that the weak residual background of the modulator produces undesired spectral ripples.

Stream temperature response to three riparian vegetation scenarios by use of a distributed temperature validated model.

Elevated in-stream temperature has led to a surge in the occurrence of parasitic intrusion proliferative kidney disease and has resulted in fish kills throughout Switzerland's waterways. Data from distributed temperature sensing (DTS) in-stream measurements for three cloud-free days in August 2007 over a 1260 m stretch of the Boiron de Merges River in southwest Switzerland were used to calibrate and validate a physically based one-dimensional stream temperature model. Stream temperature response to three distinct riparian conditions were then modeled: open, in-stream reeds, and forest cover.

Road runoff management using over-the-shoulder infiltration: real-scale experimentation.

A new management policy regarding road runoff was proposed in 2002 by the Swiss Federal Office for the Environment (FOEN). This new concept is based on the diffuse infiltration of road runoff into embankment slopes, where soils will filter particles and contaminants. The shoulder lying between road surface and infiltration slopes must be impervious in order to maximise the amount of water reaching the slope and avoid losses in the road structure.

The diffuse infiltration of road runoff: an environmental improvement.

The Laboratory of Engineering and Environmental Geology (GEOLEP) has been mandated by Swiss authorities (Swiss Federal Road Office FedRO) to test a new road runoff management concept. This concept promotes the diffuse infiltration of road runoff into infiltration slopes designed for this purpose. Soils retain particles and contaminants; this lowers the road impact on the environment and simultaneously improves aquifer recharge.

A methodology to estimate the denitrifying capacity of a riparian wetland.

Numerous studies have shown that riparian wetlands can play an important role in reducing nitrate concentrations before the ground water discharges into streams. Denitrification has been identified as an important process for this removal. Several approaches have been proposed to predict the denitrifying removal capacity of a riparian wetland, but no widely used tool exists to precisely quantify this capacity at the landscape scale.

Pathogenic-bacterial water contamination in mountainous catchments.

This space-time study of bacteriological response compared the presence of pathogens with indicators contained in surface and groundwater in mountainous regions. A systematic search for bacteria such as Listeria, Salmonella, Campylobacter and Yersinia carried out simultaneously with a search for indicators has shown that these waters can occasionally contain potentially pathogens, though these are generally to be found in small quantities. The most common pathogens found are Campyobacter and Listeria.

On the hydro-dispersive equivalence between multi-layered mineral barriers.

In the context of municipal solid waste and hazardous waste disposal, the notion of "equivalence" between different barrier designs appears in regulatory documents from several industrialized countries. While in the past, equivalence has been thought of mainly in terms of contaminant travel times, in recent years it has been defined more in terms of the magnitude of a disposal site's potential impact on groundwater resources. This paper presents some original analytical solutions to the problem of contaminant migration through a multi-layered mineral barrier.