Method and device for analysing a sample using a resonant support, illuminated by infrared radiation

A method for analyzing whether a sample includes an analyte, the sample lying on a resonant holder, the resonant holder comprising a surface on which lie a plurality of photonic crystals, which are separate from one another, and the sample being disposed between a light source and the photonic crystals, wherein:

• one resonant wavelength is associated with each photonic crystal, the resonant wavelengths of the photonic crystals defining a resonance spectral band lying between 2 μm and 20 μm;
• and
• transmission or reflection of light by each photonic crystal is maximum at the an associated resonant wavelength;
• the method comprising:
• a) illuminating the resonant holder with the light source, the light source emitting an illuminating light wave that defines an illumination spectral band that at least partially covers the resonance spectral band, wherein a plurality of photonic crystals are simultaneously illuminated;
• b) acquiring, with an image sensor, a measurement image of the resonant holder, the measurement image comprising different regions of interest, each region of interest being optically coupled to one photonic crystal such that each region of interest represents an intensity transmitted or reflected by each photonic crystal, while the resonant holder is illuminated;
• and
• then determining whether the analyte is present in the sample on the basis of the measurement image;
• wherein each photonic crystal comprises:
• first holes formed in a thin layer and having a first dimension, the first dimension being a radius or a diagonal, the first holes defining a first periodic pattern;
• second holes formed in the thin layer and having a second dimension, the second dimension being strictly smaller than the first dimension, the second holes defining a second periodic pattern;
• the second pattern and the first pattern are offset with respect to each other, parallel to the surface of the resonant holder, by a spatial offset, the spatial offset being variable between at least two different photonic crystals;
• and
• the resonant wavelength associated with each photonic crystal depends on the first dimension, on the second dimension, and on the spatial offset.