Title: Characteristics of core refractive index axial asymmetry LPFGs written by femtosecond laser

Authors: Xiaoyan Sun; Lei Liu; Youwang Hu; Jian Duan; Ping Liao; Xiaonong Zhu

Addresses: Key Laboratory of Design for Modern Complex Equipment and Extreme Manufacturing, College of Mechanical and Electrical Engineering, Central South University, Ministry of Education, Changsha, 410083, China. ' Key Laboratory of Design for Modern Complex Equipment and Extreme Manufacturing, College of Mechanical and Electrical Engineering, Central South University, Ministry of Education, Changsha, 410083, China. ' Key Laboratory of Design for Modern Complex Equipment and Extreme Manufacturing, College of Mechanical and Electrical Engineering, Central South University, Ministry of Education, Changsha, 410083, China. ' Key Laboratory of Design for Modern Complex Equipment and Extreme Manufacturing, College of Mechanical and Electrical Engineering, Central South University, Ministry of Education, Changsha, 410083, China. ' Key Laboratory of Design for Modern Complex Equipment and Extreme Manufacturing, College of Mechanical and Electrical Engineering, Central South University, Ministry of Education, Changsha, 410083, China. ' Key Laboratory of Opto-electronic Information Science and Technology, Ministry of Education, Tianjin, 300071, China; Institute of Modern Optics, Nankai University, Tianjin, 300071, China

Abstract: Direct writing of long period fibre gratings (LPFGs) in standard single mode fibres (SMF) with infrared femtosecond laser pulses is experimentally investigated. It is found that the transmission spectra of LPFGs can be controlled by infrared femtosecond laser focus condition. The transmission spectra of LPFGs present single resonance peak when the microscopic objective is 25×, which is distinct from the LPFGs manufactured by UV laser irradiation with mask. However, when the microscopic objective is 10×, the LPFGs transmission spectra with four rejection bands can be obtained. When the distribution of femtosecond laser energy is changed by inserting a diaphragm, the LPFGs transmission spectra present multi resonance peaks.

Keywords: long period fibre gratings; LPFGs; infrared femtosecond lasers; refractive index; axial asymmetry.

DOI: 10.1504/IJNM.2012.048583

International Journal of Nanomanufacturing, 2012 Vol.8 No.4, pp.340 - 347

Received: 14 Oct 2011
Accepted: 07 Mar 2012

Published online: 17 Aug 2012 *

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