Physical observation of single step UV-written integrated planar Bragg structures and their application as a refractive-index sensor

We present what is to our knowledge the first demonstration of a potentially low-cost refractive-index sensor based on UV processing. A channel waveguide and a Bragg grating are defined in a single UV processing step, resulting in a buried structure with a well-defined grating period. A subsequent wet etch process located over the Bragg grating opens a sensing window in the device and reveals the grating structure. Sensitivity of as much as 5 x 10(-6) was inferred from our device.