Gas detector, gas detection method and optical component

A gas detector, comprising:

• a space into which a target gas is supplied, the target gas exhibiting an absorption peak in an absorption spectrum;
• a light source configured to generate light having at least a wavelength belonging to the absorption peak;
• a photodetector configured to detect the light that has emitted from the light source and has propagated through the space;
• a conductive thin film on which surface plasmon polaritons are excited in response to the light from the light source and in which a plurality of optical apertures are regularly arranged such that a transmission peak in a transmission spectrum is superimposed over the absorption peak in the absorption spectrum along a wavelength axis, the transmission peak being in accordance with an interval of the regularly arranged optical apertures, the conductive thin film being able to transmit light corresponding to the transmission peak;
• a window member that intermediates propagation of the emitted light from the light source to the space, or that intermediates propagation of the light that has propagated through the space to the photodetector,
• wherein the conductive thin film is provided on the window member that is arranged on an optical path extending from the light source to the photodetector, and is provided so as to be contactable with the target gas within the space.