Microresonator Frequency Reference for Terahertz Precision Sensing and Metrology

Highly sensitive terahertz (THz) sensors for a myriad of applications are rapidly evolving. A widespread sensor concept is based on the detection of minute resonance frequency shifts due to a targeted specimen in the sensors environment. Therefore, high resolution continuous wave (CW) THz spectrometers provide powerful toolsto investigate the sensors' performances. However, unpredictable yet nonnegligible frequency drifts common to widely used optoelectronic CW THz spectrometers based on photomixers limit the sensors' accuracy for sensing and metrology. Here, we overcome thisdeficiency by introducing an ultra-high quality (Q) THz microresonator frequency reference. Measuring the sensor's frequency shift relative to a well-defined frequency reference eliminates the unwanted frequency drift, and fully exploits the capabilities of modern optoelectronic CW THz spectrometers as well as THz sensors. In a proof-of-concept experiment, we demonstrate the accurate and repeated detection of minute resonance frequency shifts of less than 5MHz at 0.6 THz of a THz microresonator sensor.