A deflection optical sensor based on a Scotch tape waveguide with an integrated grating coupler

• Published in: Sensors and actuators. A. Physical. Vol. 269; pp. 500 - 504
• Main Author: Barrios, Carlos Angulo
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.01.2018; Elsevier BV
• Subjects: Adhesive strength; Cables; Cantilever beams; Couplers; Deflection; Deflection sensor; Efficiency; Feasibility studies; Grating coupler; Incidence angle; Incident light; Interrogation; Noise; Optical measuring instruments; Optics; Photoelectric effect; Photoelectric emission; Polymer waveguide; Sensitivity; Sensitivity analysis; Sensors; Waveguide cantilever; Waveguide cantilever; Grating coupler; Deflection sensor; Polymer waveguide
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/j.sna.2017.12.013

•A waveguide cantilever with an integrated grating deflection sensor is proposed.•Cantilever deflection monitoring relies on a novel optical approach.•This approach is advantageous over an angle-dependent grating efficiency method. A deflection sensor based on a plastic waveguide cantilever is presented and demonstrated. The waveguide cantilever is made of conventional adhesive tape and integrates a metal grating coupler at its deflecting end. Light impinging the grating is coupled into the tape waveguide and guided to a fixed photodetector on which the opposite end of the waveguide is anchored. The photodiode acts as the cantilever support and converts guided optical power into a photocurrent (sensor response). Deflection optical monitoring relies on the variation of the overlap of the incident light beam spot with the grating coupler as a function of the cantilever deflection. This approach leads to a larger deflection sensitivity than that obtained by a method based just on the variation of the grating coupling efficiency with the incidence angle. A 14.85-mm-long cantilever sensor has been fabricated and exhibits a linear working range of 2 decades with a maximum deflection sensitivity of 0.2 μA/μm and a resolution of 1.7 μm, limited by the interrogation light source noise. Noise analysis indicates the feasibility of sub-nanometric deflection resolution.