3D Patterning at the Nanoscale of Fluorescent Emitters in Glass Matthieu Bellec, † Arnaud Royon, † Kevin Bourhis, ‡ Jiyeon Choi, ‡,§ Bruno Bousquet, † Mona Treguer, ‡ Thierry Cardinal, ‡ Jean-Jacques Videau, ‡ Martin Richardson, § and Lionel Canioni* ,† Centre de Physique Mole ´culaire Optique et Hertzienne, UMR 5798 CNRS, UniVersite ´ de Bordeaux, 351 cours de la Libe ´ration, 33405 Talence Cedex, France, Institut de Chimie de la Matie `re Condense ´e de BordeauxsUPR 9048 CNRS, UniVersite ´ de Bordeaux, AVenue du Dr. Schweitzer, 33608 Pessac Cedex, France, and College of Optics and Photonics/CREOL, UniVersity of Central Florida, 4000 Central Florida BouleVard, Orlando, Florida 32816 ReceiVed: May 4, 2010; ReVised Manuscript ReceiVed: July 26, 2010 Three-dimensional fluorescent nanostructures are photoinduced by a near-infrared high repetition rate femtosecond laser in a silver-containing femto-photoluminescent glass. By adjusting the laser dose (fluence, number of pulses, and repetition rate), these stabilized intense fluorescent structures, composed of silver clusters, can be achieved with a perfect control of the luminescence intensity, the emission spectrum, and the spatial distribution at the nanometer scale. This novel approach opens the way to the fabrication of stable fluorescent nanostructures in three dimensions in glass for applications in photonics and optical data storage. 1. Introduction Silver clusters stabilized in different matrixes have been reported to exhibit intense fluorescence properties. 1-4 Multiple applications have been proposed from biological labeling for clusters in water, 5 in polymer, 6 and radiation dosimetry when generated in a glass matrix. 7-9 The generation and stabilization of these species is one of the main issues. For the fabrication, two approaches have been used, starting from the metal bulk or the silver ions. In the case of the metallic thin film, silver photodissociation and oxidation give rise to the formation of silver oligomers. 10 In the case of silver ions in a solid state matrix under ionizing radiation, photographic-like processes have been carried out in order to generate electron trap and hole centers that have been identified as Ag 0 and Ag 2+ species leading later, through a migration process by chemical treatment, to the formation of Ag n nanoparticles. 11 Moreover, in the last fifteen years, direct laser writing techniques have allowed three-dimensional (3D) microstruc- turing mainly through the modification of the refractive index in transparent materials and have been widely used for photonics applications, 12 such as waveguides 13,14 and optical data storage. 15,16 Concerning the size, it has been proven that nonlinear localized polymerization allows structuring well below the diffraction limit. 17 With additional tooling costs, lithographic techniques (usually limited to 2D) can be extended also to 3D using layer- on-layer approaches to obtain nanoscale structures. 18 Recently, a technique that combines direct laser writing and metal deposition permits the creation of nanostructures. 19 However, all these techniques suffer from several drawbacks that include slow processing speeds, complexity in implementation, and the availability of materials and patterns. In this paper, we use a near-infrared (NIR) high repetition rate femtosecond laser to fabricate 3D fluorescent nanostructures with a size well below the diffraction limit in a silver-containing glass, named, hereafter, femto-photoluminescent (FPL) glass. We demonstrate that stabilized intense fluorescent structures, composed of silver clusters, can be achieved with a perfect control of the luminescence properties and the spatial distribution at the nanometer scale. 2. Experimental Methods 2.1. Glass Fabrication. Glasses with the composition 40P 2 O 5 -4Ag 2 O-55ZnO-1Ga 2 O 3 (mol %) were made using a standard melt quench technique. (NH 4 ) 2 HPO 4 , ZnO, AgNO 3 , and Ga 2 O 3 in powder form were used as raw materials, and the proper amount was placed in a platinum crucible. A heating rate of about 1 °C · min -1 was used up to 1000 °C. The melt was then kept at this last temperature (1000 °C) from 24 to 48 h. Following this step, the liquid was poured into a brass mold after a short increase of the temperature at 1100 °C in order to access the appropriate viscosity. The glass samples obtained were annealed at 320 °C (55 °C below the glass transition temperature) for 3 h, cut (0.5-1 mm thick), and optically polished. 2.2. 3D Direct Laser Structuring. The glass sample was irradiated using a femtosecond laser oscillator source emitting 470 fs, 10 MHz repetition rate pulses at 1030 nm. The laser mode is TEM 00 , M 2 ) 1.2, and the output polarization is TM. The maximum output average power is close to 5 W, which results in a maximum energy per pulse of 500 nJ. Acousto- optic filtering permits the tuning of the pulse energy, the number of pulses, and the repetition rate for control of the cumulated effects. The femtosecond laser is focused using a reflective 36× objective with a 0.52 NA (working distance ) 15 mm) at a depth of 200 μm in the glass. The beam waist is estimated to be 1 μm. The sample was manipulated using a microprecision xyz stage. 2.3. Fluorescence Microscopy. The fluorescence images and spectra were performed with a confocal microscope (Leica TCS SP2). The fluorescence lifetime was measured by a fluorescence * To whom correspondence should be addressed. E-mail: l.canioni@ cpmoh.u-bordeaux1.fr. Phone: +33 (0)5 40 00 83 25. † Centre de Physique Mole ´culaire Optique et Hertzienne, UMR 5798 CNRS, Universite ´ de Bordeaux. ‡ Institut de Chimie de la Matie `re Condense ´e de BordeauxsUPR 9048 CNRS, Universite ´ de Bordeaux. § University of Central Florida. J. Phys. Chem. C 2010, 114, 15584–15588 15584 10.1021/jp104049e  2010 American Chemical Society Published on Web 08/26/2010