Multi-passage cavity for an optical device for manipulating light radiation spatially

A multi-passage cavity, comprising:

• first and second optical elements respectively having main faces each bearing a reflective surface, the reflective surface of at least one of the first and second optical elements having a plurality of microstructured zones aligned along a general direction of progression of radiation in the cavity, the main faces facing each other so that the reflective surfaces are arranged according to a defined geometry of the multi-passage cavity, the at least one of the first and second optical elements having the reflective surface having the plurality of microstructured zones comprising a solid part and a functional layer on the solid part, the functional layer forming the reflective surface, the solid part and the functional layer having different coefficients of thermal expansion;
• and
• two spacers for assembling the first and second optical elements, each of the spacers being securely fastened to the main face of the first optical element and to the main face of the second optical element to maintain the defined geometry between the two reflective surface, the two assembly spacers extending between the first and second optical elements in the general direction of progression, the microstructured zones located between the two assembly spacers.