Abstract:We have measured the complex index of refraction of Ba(Mg1/3Ta2/3)O3, BMT, ceramics using coherent terahertz (THz) time domain spectroscopy. The dielectric properties of BMT ceramics, which were prepared via a two-step mixed oxide process or a hot isostatic press (HIP) process in 0.1–0.6 THz regime were studied. The real part of the index of refraction of BMT prepared via a two-step process was about 5.04, whereas that of BMT materials prepared via a HIP process was around 4.97. These values are similar to the real part of the index of BMT ceramics in the microwave range (n=5.0). Hipped BMT materials exhibit much larger power loss and hence lower Q-factor than two-step mixed oxide processed BMT in 0.1–0.6 THz regime.