There is a growing need for designing small self-powered devices, able to sense and deliver accurate information on the eld distribution around or inside complex media for monitoring and imaging purposes. Industrial, Scienti c and Medical sensing and imaging applications basically rely on the measurement of the di racted eld distribution created by an illuminating eld. In most cases this information is only available at a set of accessible check points, using either an array of sensors or a moving probe. The requirements of RF or DC cabling sets necessary reduce the exibility and increase the cost and complexity of the measurement system. Additionally some times the points of interest lie in locations that are physically inaccessible, or where wiring is not possible. In such cases, it is convenient the use of self-powered solution, that do not require any physical connection to instrumentations in order to retrieve the information, such as RFID-based elements.