The dielectric tensor rotation angle and optical properties of a nonlinear crystal of bismuth triborate in the millimeter-wave range

We present the thorough studies of dielectric properties of BiB3O6 (BIBO) crystal in the subterahertz range. We observe a large birefringence Δn = nZ −nX = 1.5 and the values of absorption coefficients of all three axes to be less than 0.5 cm−1 at the frequency of 0.3 THz. The difference from visible range in angle ϕ between the dielectric axis z and crystallophysical axis X is found to be more than 6°. The simulated phase-matching curves in the xz plane of the crystal show the optimal value of the angle θ to be around 25.5°±1° for an efficient millimeter-wave generation under the pump of 1064 nm laser radiation