Long Period Fiber Gratings Inscribed With an Improved Two-Dimensional Scanning Technique

We demonstrated a promising CO
₂
laser irradiation system based on an improved 2-D scanning technique. Such a system could be used to inscribe high-quality long period fiber gratings (LPFGs) with good reproducibility of grating inscription, which attributes to the fact that our system includes a CO
₂
laser with an excellent power stability of less than ±2% and a 3-D ultraprecision motorized translation stages with an excellent bidirectional repeatability value of 80 nm. Moreover, a control program with an easy-to-use operation interface was developed in our system so that a high-quality LPFG could be achieved as soon as grating parameters, such as grating pitch and number of grating periods, are entered, which has a widespread commercial value and prospects for development. Additionally, near mode fields of the CO
₂
-laser-induced LPFG were observed and simulated to investigate mode coupling in the gratings.