Abstract-Terahertz birefringence of potassium niobate crystals

V.D. Antsygin, A.A. Mamrashev, N.A. Nikolaev,

https://www.sciencedirect.com/science/article/pii/S2211379717321241

We present terahertz optical properties (refractive indices and absorption coefficients) of potassium niobate crystals measured by time-domain spectroscopy in the range of 0.2 to 2.0 THz. We observe average refractive indices n_x = 5.25, n_y = 4.8, n_z = 5.9 for corresponding optical axes X, Y, Z with the large birefringence of Δn = n_z – n_y = 1.1. We report rising absorption coefficient at higher frequencies (α ∼50 cm^-1 at 1 THz for all three axes) while the dichroism is not pronounced. Somewhat higher absorption compared to the previous results could be attributed to some polydomain structure remaining in the crystal.