Anne Fleureau

Efficient Bragg gratings in phosphosilicate and germanosilicate photonic crystal fiber

We present ArF laser-induced dynamics of Bragg grating (BG) growths in phosphosilicate-doped or germanosilicate-doped core photonic crystal fibers (PCFs). To this end, we have adapted the technique of H2 loading, usually used in conventional fiber, to the case of microstructured fiber, allowing both the concentration of hydrogen in the PCFs to be kept nearly constant for the time of the exposure and the BG spectra to be easily recorded. We compared the characteristics of BG growths in the two types of PCF to those in conventional step-index fibers. We then conducted a study of the thermal stability of the BGs in PCFs through 30 min of isochronal annealing. At the same time we discuss the role played by the microstructuration and the doping with regard to the grating contrast and the Bragg wavelength stability.

Supercontinuum Generation From 1.35 to 1.7

We experimentally study a new regime for supercontinuum (SC) generation in the nanosecond pulsed regime using a microstructured optical fiber with two zero-dispersion wavelengths (ZDWs). Pumping at 1535 nm around the second ZDW yields a nearly flat SC over 1350-1700 nm. The interplay between the effects of modulation instability and stimulated Raman scattering are described through simple phase-matching relations.

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We demonstrate a Raman laser made from a grating-free highly-nonlinear photonic crystal fiber. The laser threshold power is lower than 600 mW and laser power characteristics recorded in experiments are accurately described from the usual simplest model dealing only with stationary evolutions of total optical powers [J. Opt. Soc. Am. 69, 803-807 (1979)]. In our theoretical treatment, reflectivity coefficients are fixed parameters, in strong contrast with procedures usually implemented to describe Raman fiber lasers made with fiber Bragg gratings. Experimental investigations of the spectral properties of our grating-free Raman fiber laser evidence that the shape of the Stokes power spectrum remains remarkably Gaussian whatever the incident pump power. Increasing the incident pump power induces a drift of the Stokes wavelength together with a broadening of the Stokes optical spectrum. Investigations on the role of light polarization on laser characteristics show that our grating-free Raman fiber laser behaves as a Raman laser made with a standard polarization maintaining fiber.

m by Nanosecond Pumping Near the Second Zero- Dispersion Wavelength of a Microstructured Fiber

We evaluate the trefoil channels present between the holes of microstructured fibers as a potential dense array of small waveguides. In channels with an inner radius of 330nm, calculations indicate possible propagation with a mode waist of ~350nm at lambda=670nm, near to the diffraction limit. Actual measurements have been performed on a 1-meter fiber section, with injection by a microlensed fiber and mapping of output by near-field scanning optical microscopy. They show that light can be output in individual channels or in several of them, depending on the injection. The observed waist is ~500nm, possibly due to experimental widening. Estimated propagation losses are <20dB/m. Since each channel occupies only 2microm2, this structure opens a way to dense parallel optical processing.

Grating-free Raman laser using highly nonlinear photonic crystal fiber

We calculate the limit to which the density of two-dimensional arrays of diffraction limited fiber waveguides can be reduced while maintaining weakly-coupled characteristics. We demonstrate that this density can be experimentally reached in an array of trefoil channels formed by the air holes of a microstructured optical fiber specially designed to meet limiting size and density specifications at lambda=1.55 microm.

Light transmission in multiple or single subwavelength trefoil channels of microstructured fibers

We investigate intermodal beatings in a multimode highly asymmetric two-core microstructured optical fiber. The modal interference theory plus finite-element calculations are used to define the expected spectral signature—beat length versus propagation length—of inter- and intra-core beating. The corresponding experimental data are in excellent agreement with these predictions over 2 orders of magnitude of the propagation length. The analysis of a similar single-core fiber confirms the identification of the beatings. Therefore, a simple framework can provide an adequate picture of propagation in complex multicore microstructured fibers.

A dense array of small coupled waveguides in fiber technology: trefoil channels of microstructured optical fibers

In this paper, we present recent results concerning germanium doped highly non-linear photonic crystal fibres (HNLPCF). The finite element method is used to predict main fibre properties. The polarization behaviour of HNL-PCF is discussed in the case of disturbed numerical profiles and real fibres. Characteristics of an optimized germanium doped HNL-PCF are presented and future prospects for in-device integration are discussed as conclusion.

Intermodal interferences in a multimode highly asymmetric two-core microstructured optical fiber

Writing Bragg gratings inside the core of a photonic crystal fiber (PCF), we demonstrate an all-fiber Raman laser fully made with a highly nonlinear PCF. The laser delivers an output power of 4 Watt.

Fabrication and characterization of germanium doped highly non-linear photonic crystal fibres

In the context of accelerating FTTH deployment, the need for low bending loss single mode fibers (SMF) is growing. In the recent years, different strategies were explored to design these fibers [1–3]. Hole assisted fibers (HAF) were proposed as a solution as soon as 2003 [4], but to our knowledge no clear comparison between the different possible HAF designs and with simple standard step-index was reported to date.