Optical device and spectrometer comprising such a device

A method of determining wavelength and polarization dependent intensities of different polarization components of incoming light, the method comprising

• passing the incoming light through a filter formed by a stack of a first and second partial reflection layer and an intermediate layer between the first and second partial reflection layer, an intermediate layer between the first and second partial reflection layer, the intermediate layer comprising a dielectric material and a group of arrays of posts embedded in the dielectric material intermediate layer, the posts being of a material with light propagation properties that differ from those of the dielectric material, each array comprising a plurality of posts, the posts within each array having a same shape and orientation in cross-section with a virtual plane parallel to the reflection layers, the shape and/or orientation of the posts in different ones of the arrays in the group being different from one another, so that parts of the stack that respectively contain different ones of the arrays each form a respective optical resonator having first and second resonance peaks at different resonance frequencies for different polarization components;
• measuring a group of intensities of light obtained by passing the incoming light through respective ones of the optical resonators;
• and
• computing the wavelength and polarization dependent intensities of components of incoming light as a solution of expressions for the group of measured intensities dependent on the intensities of the different polarization components at the resonance frequencies.