Based on the electro-optic (EO) polymer Mach–Zehnder interferometer (MZI) technology, IPITEK develops optical E-field sensor devices. As a receive antenna, the present device exhibits wide and flat bandwidth, up to 10 GHz. Testing the E-field sensor response was performed using a transverse electromagnetic (TEM) cell at frequencies from 0.2 to 1 GHz, and a set of 4 horn antennas at frequencies from 2.6 to 12 GHz. The minimum detectable E-field, Emin, was about 70 mV/(m√Hz) for an all-dielectric field sensor and was about 7 mV/(m√Hz) for a sensor with electrodes and a short wire loop antenna. A photonic down-conversion technique was developed to address bandwidth and receiving power limitations of the receiver photodetector. The down-conversion experimental results agree well with the theoretical heterodyne predictions. The EO polymer sensor sensitivity can be further improved by reducing the device optical insertion loss, optimizing the photodetector and detection circuitry, and using recently developed higher EO coefficients polymers.