Q-switched operation of a 2.7 lm cladding-pumped Er 3þ /Pr 3þ codoped ZBLAN fibre laser Daniel J. Coleman a, * , Terence A. King a , Do-Kyeong Ko b , Jongmin Lee b a Laser Photonics Group, Schuster Laboratory, Department of Physics and Astronomy, University of Manchester, Brunswick St., Manchester M13 9PL, UK b Advanced Photonics Research Institute, Kwangju Institute of Science and Technology, 1 Oryong-dong, Buk-gu, Gwangju 500-712, South Korea Received 19 September 2003; received in revised form 15 November 2003; accepted 19 March 2004 Abstract We report a demonstration of Q-switched operation of a Er 3þ /Pr 3þ :ZBLAN fibre laser. Approximately an order of magnitude improvement in average power and pulse energy over previous results for Er 3þ -doped ZBLAN fibre lasers was achieved with no evidence of saturation in the output power due to amplified spontaneous emission (ASE) or excited state absorption (ESA). Pulse durations of 250 ns have been obtained and at a 19.5 kHz repetition rate a maximum average power of 19 mW has been achieved. The maximum power was limited by the speed of the mechanical Q-switch and it is likely that the overall performance of the system could be considerably by utilising a Q-switch based on an acousto-optic modulator. Ó 2004 Elsevier B.V. All rights reserved. PACS: 42.60.Gd; 42.55.Wd; 42.55.Xi Keywords: Q-switched; Fiber lasers; Diode pumped lasers 1. Introduction Pulsed 3 lm lasers have applications in gas sensing and biology due to the very high absorp- tion coefficient of water in this wavelength region. Relatively low pulse energies are required for po- tential applications in gas sensing [1] and for medical applications, average powers of several hundred mW’s are needed [2]. Since bodily tissues have a high water content 3 lm radiation can be used as a precise and efficient cutting tool for surgery [3] and laser systems operating at 2.94 lm based on Er 3þ -doped crystals [4] have already been used for this application [5–7]. Continuous wave (CW) operation of Er 3þ -doped ZBLAN fibres at 2.7 lm has been demonstrated [8] and powers up to 1.7 W have been achieved [9]. However, the * Corresponding author. Tel.: +44-161-275-4089/4292; fax: +44-161-275-4293. E-mail address: dan@fs4.ph.man.ac.uk (D.J. Coleman). 0030-4018/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.optcom.2004.03.051 Optics Communications 236 (2004) 379–385 www.elsevier.com/locate/optcom