Abstract
Here, we present a novel method to fabricate long period gratings using standard single mode optical fibers (SMF). These optical devices were fabricated in a three-step process, which consisted of etching the SMF, then coating it with a thin-film and, the final step, which involved removing sections of the coating periodically by laser ablation. Tin dioxide was chosen as the material for this study and it was sputtered using a pulsed DC sputtering system. Theoretical simulations were performed in order to select the appropriate parameters for the experiments. The responses of two different devices to different external refractive indices was studied, and the maximum sensitivity obtained was 6430 nm/RIU for external refractive indices ranging from 1.37 to 1.39.
Highlights
Long period gratings (LPGs) have been extensively studied for the last few decades [1]
Knowing that the attenuation bands in the optical spectrum are generated by the coupling of the fundamental mode to cladding modes of the LPG structure, there is a significant dependence between the properties of the external medium and the position of the attenuation bands [3]
There are more available materials, the number of fabrication steps is lower compared to corrugated LPGs [35], it can be developed in standard single mode optical fibers (SMF), and physical parameters or chemical species affecting the coating will modify the grating itself, either by changing its refractive index or by changing its size
Summary
Long period gratings (LPGs) have been extensively studied for the last few decades [1]. Other methods, based on lithography or wet-etching processes, have recently been used for the fabrication of the so-called corrugated LPGs [27,28,34,35,36,37,38] During these processes, sections with different effective indices (neff ) were obtained by periodically decreasing the cladding diameter. There are more available materials, the number of fabrication steps is lower compared to corrugated LPGs [35], it can be developed in standard SMFs, and physical parameters or chemical species affecting the coating will modify the grating itself, either by changing its refractive index or by changing its size. As a demonstration of this novel optical structure, the behavior as a refractometer was studied
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