Optical waveguide sensor and manufacturing method of the same

An optical waveguide sensor comprising:

• a substrate;
• and
• an optical waveguide including a core and a lateral clad, the core extending in a spiral shape above a surface of the substrate, the lateral clad disposed in a same layer as the core above the surface of the substrate and being in contact with either side surfaces of the core, at least a part of a surface of the core located opposite from the substrate being a transmission surface from which light leaks and is absorbed by a detected object, wherein
• the substrate has a removed section that opens on the surface of the substrate,
• portions of the core and the lateral clad bridging the removed section form a membrane, and
• both the surface of the core located opposite from the substrate and a surface of the core facing the substrate are the transmission surfaces, and further comprising:
• a support layer disposed on at least one of the transmission surfaces of the core for reinforcing the membrane, wherein
• when the light guided in the optical waveguide has a wavelength λ, the support layer has a refractive index ns at the wavelength λ, and the support layer has a thickness ts, the support layer satisfies a relationship of ns×ts≦λ.