Géraud Bouwmans

Improvements of solid-core photonic bandgap fibers by means of interstitial air holes

We report the fabrication, characterization and modeling of a solid-core photonic bandgap fiber with interstitial air holes between the cladding rods. The presence of these interstitial air holes leads to a great improvement of optical properties for this kind of fiber. Particularly, we demonstrate that confinement losses and bend sensitivity are substantially reduced. Our experimental results for this new solution are well supported by numerical results.

Dynamics of the modulation instability spectrum in optical fibers with oscillating dispersion

A simple analytical model is developed to analyze and explain the complex dynamics of the multipeak modulation instability spectrum observed in dispersion oscillating optical fibers [M. Droques et al., Opt. Lett. 37, 4832 (2012)]. We provide a simple expression for the local parametric gain, which shows that each of the multiple spectral components grows thanks to a quasi-phase-matching mechanism due to the periodicity of the waveguide parameters, in good agreement with numerical simulations and experiments. This simplified model is alsosuccessfullyusedtotailorthemultipeakmodulationinstabilityspectrumshape.Thesetheoreticalpredictions are confirmed by experiments.

Experimental investigation of combined four-wave mixing and Raman effect in the normal dispersion regime of a photonic crystal fiber

We study the effect of stimulated Raman scattering on four-wave mixing sidebands generated by pumping in the normal dispersion regime of a photonic crystal fiber. Q-switch nanosecond pulses at 1064 nm are used to generate signal and idler wavelengths by degenerate four-wave mixing. These three waves generate their own Raman Stokes orders, leading to a broadband supercontinuum.

Nanostructuring an erbium local environment inside sol–gel silica glasses: toward efficient erbium optical fiber lasers

To extend the use of erbium- (Er-)/aluminum- (Al-) codoped optical fibers in hostile environments, the reduction of the Al amount has been identified as a serious way to harden them against harsh radiation. In this work, sol–gel monolithic Er3+-doped and Er3+/Al3+-codoped silica glasses were prepared from nanoporous silica xerogels soaked in a solution containing an Er salt together or not with an Al salt. After sintering, these glasses were used as the core material of microstructured optical fibers made by the stack-and-draw method. The influence of Al incorporation on the optical properties of Er3+-doped silica glasses and fibers is investigated. This approach enabled the preparation of silica glasses containing dispersed Er3+ ions with low Al content. The obtained fibers have been tested in an all-fibered cavity laser architecture. The Er3+/Al3+-codoped fiber laser presents a maximum efficiency of 27% at 1530 nm. We show that without Al doping, the laser exhibits lower performances that depend on Er content inside the doped fiber core. The effect of Er pair-induced quenching also has been investigated through nonsaturable absorption experiments, which clearly indicate that the fraction of Er ion pairs is significantly reduced in the Al-codoped fiber.

Bending Losses in all Solid 2D Photonic Band-Gap Fibers: A limiting Factor?

Bending losses are investigated experimentally and numerically in a solid-core bandgap fiber with parabolic refractive index inclusions. Previous record of 20 dB/km is reduced to 6 dB/km by increasing the fiber bend radius.

Microbending behavior of large-effective-area Bragg fibers

We use a phase-sensitive optical low-coherence interferometry technique and camera imaging to identify microbend-induced mode couplings in Bragg fibers. Results show the importance of the quality of fabrication of Bragg fibers on their modal content when they are subject to microbends. Design strategies to improve the microbending robustness are identified.

Optical Frequency Domain Reflectometer Distributed Sensing Using Microstructured Pure Silica Optical Fibers Under Radiations

We investigated the capability of micro-structured optical fibers to develop multi-functional, remotely-controlled, Optical Frequency Domain Reflectometry (OFDR) distributed fiber based sensors to monitor temperature in nuclear power plants or high energy physics facilities. As pure-silica-core fibers are amongst the most radiation resistant waveguides, we characterized the response of two fibers with the same microstructure, one possessing a core elaborated with F300 Heraeus rod representing the state-of-the art for such fiber technology and one innovative sample based on pure sol-gel silica. Our measurements reveal that the X-ray radiations do not affect the capacity of the OFDR sensing using these fibers to monitor the temperature up to 1 MGy dose whereas the sensing distance remains affected by RIA phenomena.

Bending behaviors of all-solid silica large mode area Bragg fibers

Fibers used for high power delivery are designed to ensure single-mode operation (in order to guarantee good output beam quality), large effective areas (Aeff) and resistance to bend-induced distortions (in order to avoid non-linear effects). For simple step index fibers, the maximum Aeff of the fundamental mode that can practically be achieved at 1.06μm is ~350μm2. All-solid-silica Bragg fibers with large cores were proposed as an alternative solution for high power delivery through their fundamental core mode. These fibers consist of a low-refractive index core surrounded by a multilayer cladding that acts as a Bragg mirror. The loss spectrum of such fibers consists of a concatenation of several transmission windows separated by high-loss peaks. Here, we simultaneously study, for the first time (at our knowledge), the bending impact on Bragg fibers for the three critical properties required for high power delivery: large Aeff, single-mode propagation and low bend losses for the fundamental mode. Thanks to their specific guiding mechanism, Aeff as large as ~500μm2 at 1.06μm can be achieved in Bragg fibers, while maintaining single-mode operation and bend losses lower than 0.1dB/m. Our numerical results are validated by experimental measurements on a PCVD Bragg fiber with a 40μm diameter core.

Extended blue side of flat supercontinuum generation in PCFs with a CW Yb fiber laser

We report the generation of a broadband super- continuum with a CW Yb fiber laser and a PCF. The spectrum extends toward short wavelengths through efficient dispersive wave generation.

Bend-induced transformation of the transmission window of a large-mode-area bragg fibre

We study the effect of bends on the transmission window of the first PCVD large-mode-area Bragg fibre. The origin and the consequences of this effect are also presented.