Abdukerim Nurmemet, Grobnic Dan, Hnatovsky Cyril, Mihailov Stephen J
Opt Express. 2019 Dec 23;27(26):38259-38269. doi: 10.1364/OE.27.038259.
Tilted fiber Bragg gratings are inscribed in non-photosensitized single mode fibers through the polyimide coating using a femtosecond infrared laser and a phase mask. The inscription technique used is based on simultaneously translating the fiber along its axis and the focusing cylindrical lens in the orthogonal direction by means of piezoelectric actuators. The grating plane tilt angles up to 10.3° are achieved with a 1.07 µm-pitch phase mask. The cladding modes reach ∼5 dB in strength in transmission despite the presence of the polyimide coating. The effectiveness of the fabricated tilted fiber Bragg gratings for refractive index sensing through the polyimide coating is also demonstrated. Additionally, we show that the classical approach for the inscription of tilted Bragg gratings, which is based on simply tilting the fiber with respect to the interference fringes, cannot be used in tight focusing geometries that are necessary for through-the-coating inscription.
倾斜光纤布拉格光栅是通过聚酰亚胺涂层，利用飞秒红外激光和相位掩膜写入非光敏单模光纤中的。所采用的写入技术基于通过压电致动器使光纤沿其轴同时在正交方向上平移聚焦柱面透镜。使用间距为1.07 µm的相位掩膜可实现高达10.3°的光栅平面倾斜角。尽管存在聚酰亚胺涂层，但包层模在传输中的强度达到约5 dB。还展示了所制备的倾斜光纤布拉格光栅通过聚酰亚胺涂层进行折射率传感的有效性。此外，我们表明，基于简单地使光纤相对于干涉条纹倾斜的倾斜布拉格光栅的传统写入方法，不能用于穿透涂层写入所需的紧密聚焦几何结构中。
