Ridge Waveguide Bragg Grating Pressure Sensor

In this work, a ridge waveguide Bragg grating pressure or touch sensor is proposed. The sensor consists of an open top ridge waveguide Bragg grating with a pressure sensing film: polydimethylsiloxane (PDMS) on the waveguide surface. Under pressure, the guided mode of the waveguide accesses the film by coupling of the evanescent field. A large shift of the Bragg wavelength occurs when the effective index of the waveguide is changed by stress-indued variations in the film refractive index that are caused by increases in pressure. By monitoring the shifts of Bragg wavelengths in TE and TM modes, respectively, the external pressure change and the internal strain change in the film are measured. The sensitivities of the sensor with different waveguide structures are investigated.