Role of microstructure on guided acoustic wave Brillouin scattering in photonic crystal fibers

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Complete experimental characterization of stimulated Brillouin scattering in photonic crystal fiber

Dario Alasia, Stella Foaleng Mafang, Luc Thévenaz

We provide a complete experimental characterization of stimulated Brillouin scattering in a 160 m long solid-core photonic crystal fiber, including threshold and spectrum measurements as well as positionresolved mapping of the Brillouin frequency shift. In particular, a three-fold increase of the Brillouin threshold power is observed, in excellent agree-ment with the spectrally-broadened Brillouin gain spectrum. Distributed measurements additionally reveal that the rise of the Brillouin threshold results from the broadband nature of the gain spectrum all along the fiber and is strongly influenced by strain. Our experiments confirm that these unique fibers can be exploited for the passive control or the suppression of Brillouin scattering. © 2007 Optical Society of America.

Optical Society of America2007

Guided acoustic wave Brillouin scattering in photonic crystal fibers

We experimentally investigate guided acoustic wave Brillouin scattering in several photonic crystal fibers by use of the so-called fiber loop mirror technique and show a completely different dynamics with respect to standard all-silica fibers. In addition to the suppression of most acoustic phonons, we show that forward Brillouin scattering in photonic crystal fibers is substantially enhanced only for the fundamental acoustic phonon because of efficient transverse acousto-optic field overlap. The results of our numerical simulations reveal that this high-frequency phonon is indeed trapped within the fiber core by the air-hole microstructure, in good agreement with experimental measurements.

Optical Society of America2007

Effect of inhomogeneities on backward and forward Brillouin scattering in Photonic Crystal Fibers

Luc Thévenaz

Photonic Crystal Fibers (PCF) play a crucial role for fundamental investigations such as acousto-optical interactions as well as for applications, such as distributed sensors. One limiting factor for these experiments is the fiber inhomogeneity owing to the drawing process. In this paper we study the effect of structural irregularities on both the backward and forward Brillouin scattering by comparing two PCFs drawn with different parameters, in order to minimize diameter fluctuations. We fully characterize their Brillouin properties including the backward Brillouin spectrum, the Brillouin threshold, a distributed measurement along the fibers and polarized Guided Acoustic Wave Brillouin Scattering (GAWBS). In the Brillouin spectrum we observe a single peak as in a single-mode fiber whereas former investigations have often shown a multiple peak spectrum in PCFs with small core. The theoretical and experimental values for the Brillouin threshold are in good agreement, which results from the single peak spectrum. By using a Brillouin echoes distributed sensing system (BEDS), we also investigate the Brillouin spectrum along the fiber with a high spatial resolution of 30 cm. Our results reveal a clear-cut difference between the distributed measurements in the two fibers and confirm the previous experiments. In the same way the GAWBS allows us to estimate the uniformity of the fibers. The spectra show a main peak at about 750 MHz, in accordance with theoretical simulations of the acoustic mode and of the elasto-optical coefficient. The fiber inhomogeneity impacts on the stability and the quality factor of the measured GAWBS spectra. We finally show that the peak frequency of the trapped acoustic mode is more related to the optical effective area rather than the core diameter of the PCF. Thus measuring the main GAWBS peak can be applied for the precise measurement of the effective area of PCFs. © 2010 SPIE.

2010

Effect of inhomogeneities on backward and forward Brillouin scattering in Photonic Crystal Fibers

Luc Thévenaz

2010