Complex Permittivity Measurements with Quasioptical Fabry-Pérot Resonators

As millimeter instrumentalists push the precision and mapping speed of their instruments ever-higher to make ever-deeper measurements, the need for a precise understanding of the complex permittivity of the dielectrics used in these instruments at their operating temperature heightens. To address this need, we have developed high quality factor quasioptical Fabry-Pérot open resonators spanning 75 GHz-330 GHz, optimized for rapid use in a quick-turnaround 4K cryostat. These hemispherical resonators enable precise metrology of low-loss bulk and thin dielectrics. We present the design and characterization of, and some complex permittivity measurements from, a W-band open resonator.