Fabrication of fiber Bragg gratings with precisely adjustable and controllable parameters based on 213nm solid-state laser

摘要

Fiber Bragg Gratings (FBG) have great significance in the development of high-power fiber laser systems. Fabrication sources, fibers, and fabrication technology would affect the performance of FBGs directly. In this research, a scanning exposure method for fabricating FBGs in different types of photosensitive fibers with a 213nm solid-state laser source was proposed. The Q-switched Nd: YVO4 laser fifth harmonic source was compared with the traditional excimer lasers and the impacts of lengths, center wavelengths, titled angles, and apodization on the reflection and transmission spectra of FBGs were discussed. The scanning fabrication system, which can realize the tilting of phase mask and the adjustment and monitoring of tension, was built according to the characteristics that the output spot diameter of the fabrication source was sub-millimeter. While the high quality of fabrication was guaranteed, FBGs with lengths of 3mm～20mm, center wavelengths shift of 0nm～4.2nm, and tilted angles of 0～21° were obtained, and all the parameters were simultaneously adjusted and controlled, the deepest transmission loss of about -70dB. FBGs fabricated were of good stability and repeatability, especially in hydrogen fibers whose stability was independent of high-temperature annealing (150°C) which was different from the fabrication results of excimer laser sources. Then the unconformity between experimental results and theoretical simulation was discussed and the optimization schemes were proposed. The experimental results and analysis provided a better experimental scheme for UV laser fabricating FBGs and the experimental basis for further optimizing the fabrication technology and further analyzing the microscopic mechanism of optical fiber photosensitivity.