Characteristic control of long period fiber grating (LPFG) fabricated by infrared femtosecond laser

Abstract

Long period fiber gratings (LPFGs) with different spectral characteristics were fabricated with 1 kHz, 50 fs laser pulses. The contrast of resonant rejection band can be significantly increased by a proper amount of axial stress along a fiber during laser writing or post-processing with lower energy density laser irradiation. Variations of focal condition, pulse energy of laser irradiation and the number of grating periods lead to the generation of resonance rejection band of LPFGs from single-peak to multi-peak plus larger out-of-band loss. The out-of-band loss is primarily caused by Mie scattering from the laser processed cites, and it can be reduced by decreasing the duty cycle of grating pitch instead of lowing down the actual power of laser irradiation.

Keywords

long-period fiber grating (LPFG) / infrared femtosecond laser / out-of-band loss / Mie scattering / micro-nano-fabrication

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Acknowledgements

This research was supported by the National Natural Science Foundation of China (Grant Nos. 61137001, 51005250, 11004111), the Basic Research in Nano-manufacturing Program of National Natural Science Foundation of China (No. 90923030 and No. 91123035), and the Tianjin Natural Science Foundation (No. 10JCZDGX35100). We thank Y. G. Liu for the use of some of her fiber optic equipment and K. H. Xu for technical assistance in the laboratory.

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2014 Higher Education Press and Springer-Verlag Berlin Heidelberg