By Innofocus Photonics Technology Pty Ltd
The area that inscribed affects FBG’s performance. Therefore, it is especially important to increase the FBG inscribed area for large core diameter fibers. There are two methods to increase the FBG inscribed area: 1. Conventional laser fabricating systems without beam shaping function, are able to achieve inscribing in large area through line-by-line method, where the area is determined by the length of the laser focus (along the z-direction, which is the direction of the optical axis) and the length of the swept line segment (x or y-direction, which is the direction of the writing line). If a large area is required, lens with a lower numerical aperture (NA) can be used (to increase the length of the focal point) as well as writing longer lines (to increase the length of the written line segment). This method inscribes in a square interface, and the writing time is relatively long. Thus, it requires longer processing time. 2. With the support of Innofocus’s unique beam shaping function, we can adjust the beam focus and extend one of the focus dimensions (perpendicular to the fiber core direction) to inscribe in a pancake-shape focus. This method inscribes in a circular interface. Furthermore, this method can directly adjust the focus to match the specific parameters of the fiber core. The advantage of using this method is that it enables high-speed processing of FBGs with point-by-point writing.
