Low temperature complex permittivity of MgF/sub 2/ at microwave frequencies from TE/sub 01/spl delta// modes

MgF/sub 2/ is a hard and birefringent crystal with low refractive index and a wide transmission range and is widely used in prisms and optical windows. The RF and microwave losses of magnesium fluoride (MgF/sub 2/) crystal are low as compared to other fluorides but not well investigated. In this paper the complex permittivity of MgF/sub 2/ studied using a TE/sub 01/spl delta// dielectric post resonator technique as a function of frequency and temperature is reported. Measured values of perpendicular component of the real part of permittivity are 5.41 and 5.33 and of the loss tangent are 1/spl times/10/sup -6/ and 2.7/spl times/10/sup -6/ at frequencies 9.2 and 20.5 GHz respectively at a temperature of 15K.