+1/-1 order phase masks (FBG)

Ibsen’s +1/-1 order principle phase masks ensure quality and facilitate production in the telecommunications, sensor, and laser industries. In the production of fiber and waveguide Bragg gratings, the phase mask is illuminated by a high-power UV laser, typically an excimer laser or frequency-doubled gas laser. Self-interference between the diffracted orders produces the required pitch in the fiber or waveguide.

Any deviation from the desired grating structure in the Phase mask is transferred directly to the fiber or waveguide. It is therefore imperative that the Phase mask pitch is accurate, uniform, and defect-free. Through scientific principles and constants of nature, our fabrication process ensures absolute pitch accuracy. In addition, geometric principles in our production equipment ensure strict uniformity, eliminating e-beam drawbacks such as stitching errors and field distortion.

Other important features of our line of +1/-1 order Phase masks are:

Using the +1/-1 order principle, the phase mask is optimized to diffract light equally and maximally into the plus first and minus first orders. Self-interference between these two orders creates an interference pattern with half the pitch of the phase mask pitch. As the diagram illustrates, a +1/-1 order phase mask can generate additional unwanted orders. Ibsen phase masks have highly suppressed zero order noise. The main advantage of this +1/-1 order principle (relative to the 0/-1 order principle) is its ease of use with normally incident illumination.