Fiber optic microsensor for micro-wave and millimeter wave electric fields

A new non-disturbing photonic probe for measuring electromagnetic fields is proposed and tested. The antenna is based on a temperature interferometric microsensor. The sensing element is made of a silicon Fabry-Perot optical microcavity connected to an optical fiber for remote interrogation. When ex posed to an Electro-Magnetic (EM! field. the power dissipated in the semico nductor sensing element induces the heating, and in rum, a change of the re fractive index of the silicon by thermo-optic effect. This variation induce s a modulation of the probing light intensity reflected or transmitted by t he interferometric cavity. Preliminary measurements carried out in the freq uency range 1-18 GHz hare shown the capability to detect minimum electric f ields of the order of few tens of volts per meter. This resolution can be g reatly enhanced by optimizing the sensor design. Moreover, theoretical resu lts show the interesting performance of a flat frequency response at freque ncies greater than about 20 GHz. Finally. the microsensor is realized in th e low cost and reliable microelectronic technology. and could be integrated on chip with other opto-electronic devices.