DEVICE AND METHOD FOR OBSERVING A FLUORESCENT SAMPLE

A method for observing a fluorescent sample, the sample comprising a fluorescent agent that emits fluorescence light, in a fluorescence spectral band, when it is illuminated by excitation light, in an excitation spectral band, the method comprising the following steps:a) placing the sample on a holder;b) illuminating the sample, with an excitation light source, in the excitation spectral band, the light emitted by the light source propagating along a propagation axis;c) detecting fluorescence light, in the fluorescence spectral band, with an image sensor;the method being such that the holder comprises a thin layer formed from a first material, of a first refractive index, the thin layer lying in a holder plane perpendicular to the propagation axis, the thin layer comprising a first photonic crystal and second photonic crystals configured to confine the excitation light and the fluorescence light in the thin layer.