Thermo-optic designs for electromagnetic-field probes for microwaves and millimeter waves

The development of an electromagnetic-field probe for microwave and millimeter-wave frequencies is reported. The probe uses an optically sensed thermometer to measure the heating of a resistive element in an electromagnetic field. The response is calculated for several different configurations of the resistive element, and two optimal designs are chosen. Measurements on experimental probes of these designs are presented. One of the designs displays a flat frequency response above 30 GHz and a sensitivity of 38 V/m. Improvements in the design are identified that should significantly increase the sensitivity and improve the low-frequency response