Optical Pressure Sensors Based on Vertical Directional Coupling With Flexible Polymer Waveguides

An optical pressure sensor based on the radiation coupling in vertical direction between a channel waveguide and a flexible polymer waveguide is proposed. The flexible waveguide is bent by an applied pressure to reduce the separation distance between the two waveguides so that the light propagating in the channel waveguide is radiated into the flexible planar waveguide. By applying a pressure ranging from 100 to 500 kPa, the output intensity modulation of 20 dB is obtained by virtue of the efficient phase matched coupling between the waveguides made of the same polymer material. The large extinction ratio is useful to measure the pressure precisely for a wide range.