2015-05-042015-05-042012-11-13Mendis, Rajind and Mittleman, Daniel M., "Resonant cavity integrated into a waveguide for terahertz sensing." Patent US8309925B2. issued 2012-11-13. Retrieved from https://hdl.handle.net/1911/80105.https://hdl.handle.net/1911/80105A method comprising polarizing and coupling an electromagnetic beam to a first-order transverse electric (TE1) mode with respect to a parallel plate waveguide (PPWG) integrated resonator comprising two plates and a cavity, sending the electromagnetic beam into the PPWG integrated resonator to excite the cavity by the TE1 mode and cause a resonance response, and obtaining wave amplitude data that comprises a resonant frequency, and obtaining the refractive index of fluids filling the cavity via the shift in resonant frequency.25 ppengUtility patentUS8309925B2