Femtosecond laser three-dimensional microstructuring inside photosensitive glasses B. Fisette and M. Meunier, Laser Processing Laboratory, Department of Engineering Physics, École Polytechnique de Montréal, Case Postale 6079, succ. Centre-ville, Montréal (Québec), H3C 3A7, Canada ABSTRACT Femtosecond laser is used to form three-dimensional (3D) microstructures embedded in Foturan, a photosensitive glass. The microstructures are realized using a three steps process including infrared femtosecond exposure, heating process and etching in an ultrasonic solution of hydrofluoric acid in water. The experiments were carried out using a specially designed ultrafast laser micromachining station, which included a femtosecond laser (Spectra Physics, 170fs, 800nm, 1 mJ/pulse at repetition rate of 1kHz), systems for the delivery, high-precision focusing and spatial-temporal control of the laser beam, and a fully automated and programmed system for the precise target positioning over a prescribed 3D trajectory. Efficiency of the fabrication process is discussed in terms of the various laser and etching fabrication parameters. An example of the fabrication of a 3D microfluidic system for biomedical applications is presented. Keywords: Femtosecond laser, 3D microfabrication, photosensitive glass, microchannel. 1. INTRODUCTION Photosensitive glasses, which were developed at Corning Glass Works in 1947 1 , have very interesting properties for of the fabrication of microsystems, such as a high Young’s Modulus, a low absorption coefficient in the visible wavelengths and a good chemical stability and biocompatibility. They are now used in many technological applications, including GEM-Type detectors 2 , hydrodynamic microelectrochemical reactor for voltammetric sensing of chemical species 3 , nanotube-based field emission flat panel display 4 , ultra-long glass tips for atomic force microscopy 5 and nanosatellites 6 . In the past, FOTURAN, and other photosensitive glasses, has been mostly process using either Hg lamp 5,7 and UV laser 8,9 . Since the FOTURAN’s transmittivity is low for UV photons, these methods permit to fabricate microstructures only on the «surface» of the sample. To fabricate real 3-D microstructures, Kondo et al 10 and Cheng et al 11 used an infrared femtosecond laser for which the FOTURAN is transparent except at the focussing point where multiphoton absorption occurs leading to a local phase transformation in the glass. With this process, embedded deep 3D structures such as Y or U shaped inter channels have been produced 10,11 . In this paper, we used the femtoseconde laser to fabricate 3-D microstructures in FOTURAN. A systematic study of the relation between the size of the microstructures and the laser parameters and a discussion on the basic mechanism of photosensitization of Foturan are presented. A three-dimensional microstructure including channels with varying controlled diameter for microfluidic applications is presented. 2. PRINCIPLES OF THE MICROSTRUCTURING FOTURAN, manufactured by Schott glass Co, is a lithium aluminosilicate photosensitive glass doped with some silver, cerium, and antimony. The main idea behind processing of FOTURAN is to light induce a lo- Photonics North 2004: Photonic Applications in Astronomy, Biomedicine, Imaging, Materials Processing, and Education, edited by J. C. Armitage, R. A. Lessard, G. A. Lampropoulos, Proc. of SPIE Vol. 5578 (SPIE, Bellingham, WA, 2004) · 0277-786X/04/$15 · doi: 10.1117/12.567244 677