The invention relates to a sensor device and a corresponding method for measuring an electromagnetic field (10) by means of- a sensor unit (1) comprising a medium (2), which can absorb energy from the electromagnetic field (10) and which exhibits transient thermal expansion upon absorption of energy from the electromagnetic field (10), whereby acoustic waves, in particular ultrasonic waves, are generated, and a detector (3) for detecting the acoustic waves and for generating according detector signals and- a processing unit (4) for deriving at least one property of the electromagnetic field (10) from the detector signals.The sensor device and method according to the invention allow for measuring electromagnetic fields in free space, ambience, matter and biological tissue in a simple and reliable way.
