Structuring the matter has appeared for several decades as an essential step in the quest for more and more efficient optical devices. Hence, this presentation will focus on the benefit of structuring glasses and fibres at the nanoscale for the achievement of optical amplifiers and laser devices. To this end, two approaches will be presented: 1. The first one relies on the use of the sol-gel polymeric route to prepare nanoporous silica xerogels that can be applied to the preparation of high purity silica glass rods for the achievement of photonic crystal fibers (PCFs) cores with conventional and unconventional composition. As an example, results on the synthesis of Erbium and Ytterbium-doped rods and their characterization will be presented. These rods have been used to fabricate PCFs with Er3+ and Yb3+-doped pure silica cores. Effects of this synthesis on the spectroscopic properties of the rare-earth ions will be discussed together with the performances of the doped PCFs employed as amplifiers or laser sources [1]. Recently, we demonstrated that the polymeric Sol-Gel route combined to elaboration of PCF by Stack and Draw can be used to realize efficient ytterbium-doped fiber laser based on pure silica matrix [2]. More precisely, a pure silica ytterbium-doped photonic crystal fiber with a core obtained from the Sol-Gel polymeric technique is studied and more than 73% laser efficiency is achieved for a laser emission around 1034 nm. The dimensions of the ytterbium-doped monolith combined to the uniform doping and refractive index that are achieved make the Sol-Gel polymeric technique particularly interesting for the realization of LMA fibers. 2. The second approach is based on the use of alumina-based nanoparticles synthesized by a soft chemical way, enabling the control of their composition and size before their incorporation within core fiber through a liquid doping technique fully compatible with Modified Chemical Vapor Deposition (MCVD) technology[3]. Nanoparticle integrity over fiber manufacturing process is ensured thanks to a thermal strengthening step involving alumina phase transformation. Resulting erbium-doped fibers showing a standard WDM C-Band shape with a much lower aluminum content have been obtained. They are also characterized by an unprecedented low background attenuation losses and a high erbium doping homogeneity along the fiber length, having a strong impact on process repeatability and fiber manufacturing cost. Such fibers have also shown an increased amplifying medium efficiency compared to conventional doped fibers. 1. H. El Hamzaoui, L. Bigot, G. Bouwmans, I. Razdobreev, M. Bouazaoui and B. Capoen, “From molecular precursors in solution to microstructured optical fiber: a sol-gel polymeric route” , Opt. Mat. Express 1, pp. 234-242 (2011). 2. A. Baz, H. El Hamzaoui, I. Fsaifes, G. Bouwmans, M. Bouazaoui, L. Bigot, “Pure silica Ytterbium-doped Sol-Gel-based fiber laser” , Laser Physics Letters , vol. 10, no 5, pp. 055106-055110 (2013). 3. Boivin, D.; Pastouret, A.; Burov, E.; Gonnet, C.; Cavani, O.; Lempereur, S.; Sillard, P.; “Performance characterization of new erbium doped fibers using MCVD nanoparticle doping process”, Proc. of Spie 2011, 7914, 791423.