A light emitting structure for a photo-acoustic spectroscopy sensing device for sensing a target gas comprises a light source configured for emitting light of an input wavelength. The light emitting structure further comprises a conversion structure that is configured for absorbing light of the input wavelength, and that is further configured for emitting light of an output wavelength. The output wavelength of the conversion structure is adapted to an absorption wavelength of the target gas. The conversion structure comprises an output conversion layer that comprises a plurality of nanoparticles. The nanoparticles of the output conversion layer are configured for emitting light of the output wavelength.