Optical evanescent field sensor based on point-by-point laser inscribed Bragg grating in planar polymer ridge waveguide

We present a novel planar polymer ridge waveguide evanescent sensor for lab-on-a-chip applications. The integrated sensor is based on post-processing of Bragg gratings for the near-infrared (NIR) wavelength range by applying a femtosecond laser point-by-point (pbp) inscription technique. In general, this pbp inscription method offers a flexible selection of the Bragg grating wavelength from UV to NIR. The optical evanescent field sensor was tested with different substances with different refractive indices, demonstrating an increased sensitivity. Finally, the sensor was coated with palladium nanoparticles. With this functional coating, the polymer Bragg grating sensor is capable of hydrogen detection up to 4% concentration.