Nan Ying-Gang, Kinet Damien, Chah Karima, Chapalo Ivan, Caucheteur Christophe, Mégret Patrice
Opt Express. 2021 Aug 2;29(16):25824-25835. doi: 10.1364/OE.428592.
Fiber Bragg gratings (FBGs) in cyclic transparent fluoropolymer (CYTOP) optical fiber are the subject of a lot of research as they can be of interest for many applications, such as temperature, humidity, strain, and radiation sensing. We report here a new technique to produce high quality FBGs in CYTOP fiber. It uses a femtosecond laser system operating at 400 nm and a phase mask. In contrast to previously reported results, the gratings are obtained in a few seconds with a writing power as low as 80 μW. With this setup, 2 mm-long gratings with reflectivity up to 92 % and full width at half maximum bandwidth around 0.5 nm were obtained in less than 10 s. The resonance wavelengths of the FBGs are confirmed by numerical computation in the graded-index multimode CYTOP fiber, and the mode selection characteristic of FBGs in CYTOP is investigated. Finally, the temperature sensitivity of CYTOP FBG is measured in different mode groups for heating up and cooling down, showing values independent of the mode group measured, but with a small hysteresis.
环状透明含氟聚合物（CYTOP）光纤中的光纤布拉格光栅（FBG）是众多研究的主题，因为它们在许多应用中具有吸引力，例如温度、湿度、应变和辐射传感。我们在此报告一种在CYTOP光纤中制造高质量FBG的新技术。它使用工作在400nm的飞秒激光系统和相位掩膜。与先前报道的结果相比，只需几秒钟就能以低至80μW的写入功率获得光栅。通过这种设置，在不到10秒的时间内获得了反射率高达92%、半高宽带宽约为0.5nm的2mm长光栅。通过在渐变折射率多模CYTOP光纤中的数值计算确认了FBG的共振波长，并研究了CYTOP中FBG的模式选择特性。最后，测量了CYTOP FBG在不同模式组中升温及降温时的温度灵敏度，结果表明其值与所测量的模式组无关，但存在小的滞后现象。
