Utilizing experimental results that demonstrate the presence of both Faraday rotation and electric-field-induced linear birefringence in a diluted-magnetic-semiconductor crystal of cadmium manganese telluride (CMT), a single probe that is capable of sensing both electric and magnetic fields independently has been developed. An ultrafast pulsed laser is combined with an harmonic-mixing technique using the Fourier-series components of the laser beam to demonstrate millimeter-wave field measurements exceeding 100 GHz in frequency. A higher field sensitivity and greater accuracy are observed for the CMT crystal when compared to a lithium tantalate electro-optic crystal and terbium gallium garnet magneto-optic crystal. Linear electro-optic coefficients, such as those for CMT that have not otherwise been reported in the literature, may be calculated from the electric-field measurements.

In an effort to increase the measurement sensitivity of electro-optic microwave-field sensing, a simplified electro-optic sensor/modulation system that employs a wavelength-tunable laser diode and an electro-optic-crystal microcavity has been developed. A theoretical model simulating a Fabry-Perot-based, Pockels-effect probe demonstrates that both the electro-optic phase retardation and modulation-efficiency slope of the optical system can be resonantly enhanced. Consequently, we have predicted that electric-field measurements are possible using a configuration that eliminates the polarizer, analyzer, and quarter-wave retarder of typical electro-optic intensity modulators. An experimental verification of the concept has been conducted using thin, uncoated, lithium tantalate crystals, and an electro-optic modulation signal that is ~60 dB above the system noise floor was obtained.