BaMgF4 single crystal has becoming a promising competitor in the fabrication of VUV (vacuum ultraviolet) all solid-state lasers for its very short UV absorption edge (~130 nm) and good ferroelectric properties (for quasi-phase matching). The ferroelectric, second-order, and third-order nonlinear properties of BaMgF4 crystal have been studied by researchers. BaMgF4 crystal belongs to the orthorhombic crystal system. The space group is Cmc21 and the point group is mm2.

We have fabricated a SMCW (symmetric metal-cladding waveguide) of BaMgF4 crystal and have studied the EO (electric optic) effects by using the advantage of SMCW’s high sensitivity. In our experiment, we measured various external incidence angles when changing the applied voltages corresponding to the same guided mode. The EO coefficient γ_13=-36.2pm/V is calculated by a linear fitting. Under the same experimental condition, γ_13=9.1pm/V of LiNbO3 crystal was also measured and this result is in good agreement with previous reports. The |γ_13| of BaMgF4 is even larger than the largest one γ_51=32.6pm/V of LiNbO3. We believe BaMgF4 crystal could be one of the EO crystal candidates in the fabrication of EO modulator, switches, and highly dense memories, especially in VUV region.

This research was reported by “Zhuo Wang, Hailang Dai, Yuanlin Zheng, and Xianfeng Chen, Measurement of the electro-optic coefficient of a BaMgF4 single crystal, Optics Materials Express 7(2), 360-365”