Sensor device and a method of detecting a component in gas

A sensor device comprising;

• a planar substrate defining a substrate plane,
• a waveguide for guiding an electromagnetic wave, the waveguide extending in a length direction in a waveguide plane parallel to the substrate plane, the waveguide having a width in the waveguide plane in a direction perpendicular to the length direction, and a height out of the waveguide plane in a direction perpendicular to the length direction, wherein the width to height ratio is more than 5,
• wherein the height of the waveguide is less than the wavelength of the electromagnetic wave,
• wherein the waveguide is supported on the substrate by a support structure extending from the substrate to the waveguide, along the length direction of the waveguide, having a width which is smaller than the width of the waveguide, at the point of support of the waveguide, wherein the width of the waveguide is varied along the length direction of the waveguide, and wherein the width of the support structure varies correspondingly along the length direction of the waveguide, and wherein the waveguide is of a material of a first composition and the support structure is of a material of a second composition.