Design and Fabrication of Long-period Gratings in As2S3 Chalcogenide Glass Rib Waveguides

In this paper we present high quality long-period gratings (LPG) based band-rejection filters in a highly nonlinear As₂S₃ chalcogenide glass rib waveguide. The 5 cm long rib waveguides with a rib height H, slab height h and width W of 2.56 mum, 1.53 mum and 6.44 mum, respectively, support several higher order modes. Using a Bragg grating written into the waveguide with a scanning Sagnac-Interferometer the mode structure of the waveguides are analyzed and compared to simulations using a beam propagation method. This allows the design of a LPG at telecommunication wavelengths. The refractive index LPGs were produced by a simple shadow mask technique. The writing setup allows for in situ monitoring so that the growing behavior can be studied.