A phase shift detector includes: an interferometer; and a microwave probe in electrical communication with the interferometer, the microwave probe including: a primary shield electrode; and a transmission electrode disposed proximate to the primary shield electrode, the transmission electrode and the primary shield electrode being exposed and arranged to produce an electric field, wherein the transmission electrode is isolated electrically from the primary shield electrode. A process for acquiring phase shift data includes: receiving a microwave radiation by a power splitter; producing a reference microwave radiation and a sample microwave radiation; communicating the reference microwave radiation to a reference arm; communicating the sample radiation to a sample arm; communicating the sample radiation from the sample arm to a microwave probe; subjecting a sample to the sample microwave radiation; producing a probe microwave radiation in response to subjecting the sample to the sample microwave radiation; communicating the probe microwave radiation to a power combiner; receiving the probe microwave radiation and the reference microwave radiation from the reference arm; and producing an interferometer signal in response to receiving the probe microwave radiation and the reference microwave radiation to acquire phase shift data.