A progress review of proton beam writing applications in microphotonics A.A. Bettiol a, * , T.C. Sum a , F.C. Cheong b , C.H. Sow b , S. Venugopal Rao a , J.A. van Kan a , E.J. Teo a , K. Ansari a , F. Watt a a Centre for Ion Beam Applications, Department of Physics, National University of Singapore, Singapore 117652, Singapore b Colloid Lab, Department of Physics, National University of Singapore, Singapore 117652, Singapore Available online 7 April 2005 Abstract The proton beam writing technique is a direct write lithographic technique that is being actively developed at the Centre for Ion Beam Applications, National University of Singapore for microphotonic applications. The technique utilizes a highly focused beam of MeV protons to pattern or modify the refractive index of various materials including polymers, glasses and other inorganic crystals. The technique has been applied to the fabrication of several different types of microoptical components including waveguides, gratings, microlens arrays and colloidal crystal templates. In this paper we give a review of the progress made thus far by our group and other workers in the field of micropho- tonics using proton beam writing. Ó 2005 Elsevier B.V. All rights reserved. PACS: 07.78.+s; 42.79.Bh; 42.79.Dj Keywords: Proton beam writing; Photonics; Waveguides; Gratings; Microlens arrays 1. Introduction Proton beam writing is a direct write litho- graphic technique where a highly focused beam of protons is used to pattern various types of sub- strates. The technique has been actively developed in the last 5 years or so at the Centre for Ion Beam Applications, National University of Singapore [1] where a dedicated beamline and end station has been commissioned [2]. Recently several other pro- ton beam writing facilities have come online at various laboratories around the world [3,4]. The main application areas for proton beam writing thus far include microfluidics, tissue engineering substrates [5], fabrication of stamps for nanoim- print technology [6] and microphotonics [7,8]. 0168-583X/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2005.01.084 * Corresponding author. Tel.: +65 6874 4138; fax: +65 6777 6126. E-mail address: phybaa@nus.edu.sg (A.A. Bettiol). Nuclear Instruments and Methods in Physics Research B 231 (2005) 364–371 www.elsevier.com/locate/nimb