We demonstrate a compact electromagnetic power sensor based on force effects of electromagnetic radiation onto a highly reflective mirror surface. Unlike the conventional power measurement approach, the photons are not absorbed and can be further used in the investigated system. In addition, the exerted force is frequency-independent, yielding a wide measurement frequency span being practically limited by the wavelength-dependent mirror reflection coefficient. The mechanical arrangement of two sensing elements in tandem suppresses the influence of gravity and vibrations on the power reading. We achieve a noise floor of about 1 W/√Hz and speed of 100 ms, being practically limited by sensor’s dynamics and lock-in amplifier filter settling time.
