First demonstration of a laser emission in hybrid nanostructured optical fibres based on SiO2/SnO2 system doped by ytterbium ions

Summary form only given. Recent years, researches have shown that it is possible to achieve nanostructured core fibres by incorporating dielectric [1,2], metallic nanoparticles such as Au, or quantum dots [3] in an amorphous matrix. These nanoparticles dispersed in a silica matrix present the advantage to accept a high concentration of doping ions such as rare-earth (RE) ions avoiding the quenching phenomenon, which allows to demonstrate a great potential in optical amplification. Zirconia nanoparticles have been successfully incorporated by G. Brasse et al. with the sol-gel method [1] and by Kir'Yanov et al. using the Modified Chemical Vapor Deposition (MCVD) [2]. The laser effect has been demonstrated in this Yb doped optical fibre. The incorporation of semiconductor nanoparticles in the core of the optical fibre is a challenge to get original optical properties such as original wavelength emission. Tin oxide appears as an interesting candidate due to its low phonon energy (700 cm
^-1
) and its high refractive index (1.99 at 632nm). Moreover, energy transfer can be observed in this kind of nanoparticles doped with rare earth ions, which leads to original luminescence [4,5].In this paper, we present the first fabrication of a SiO2/SnO2 nanostructured optical fibre. A fibre with a core composed of 60% mol SiO240% mol SnO2 doped with 1.6% mol ytterbium ions has been fabricated by the sol-gel chemical synthesis associated to the drawing fibre process. A study of the microstructural properties has been carried out using high resolution X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that 4 - 6 nm diameter SnO2 nanoparticles are crystallized in the rutile phase in the amorphous silica matrix (Fig. 1a). The optical properties of the nanostructured fibre have been investigated: the losses are lower than 0.5 dB.m-1 and the maximum refractive index difference is about 2.5 .10-2 at 668 nm (Fig. 1b). The presence of these particles ensures a modification of the Yb3+ ions environment and then, we have demonstrated a laser effect. An original laser emission in a short 4%-100% cavity has been achieved at 1050nm (Lfibre: 20.5cm): a 3.18 mW.μm-2 threshold with a 8% yield (Fig. 1b) is obtained. This result is a milestone toward the realization of a laser with an original nanostructured fibre by optimizing the nanoparticles concentration.