A new non-disturbing optically interrogated silicon sensor for measuring el
ectromagnetic power in the microwave and millimetre-wave range is presented
. A prototype was realised and then tested in the microwave frequency range
2.5-18GHz. A minimum detectable electromagnetic power density of similar t
o 1.4mW/cm(2) was measured. Higher performances are expected, according to
simulations, in optimised devices.