and 0 5 micrometer are also provided on conductive layer 66 with surfaces opposite to first bowtie antenna 54 fins 70 72 74 are thus capacitively coupled with antenna 54 and are further selected to perform an impedance matching therewith in a way which will be explained in detail hereinafter more specifically distance e separating antennas 54 and microbridge 56 ranges between 0 5 and 5 micrometers and is preferably equal to 2 micrometers for mechanical hold reasons distance e is selected to perform a high performance capacitive coupling between first antenna 54 deposited on substrate 52 and fins 70 72 74 this thickness is preferably selected to be as low as possible while being compatible with the mechanical hold of microbridge 56 to provide the thermal insulation fins 70 72 74 as well as the portion of second bowtie antenna 68 arranged in central portion 60 are covered with an insulator layer 76 to electrically insulate them a portion of conductive layer 66 being left exposed layer 76 is for example formed of a layer of sin sio zns or other of a thickness ranging between 0 005 and 0 1 micrometer a layer of thermometric material 78 is further deposited on insulator layer 76 in contact with conductive layer 66 at the level of the portion thereof left exposed by insulator layer 76 the material forming thermometric element 78 for example is an amorphous or polycrystal semiconductor such as si ge sic a si h a sige h a metallic material or also a vanadium oxide or a magnetite oxide this material should have a non zero temperature coefficient resistance tcr in other words.