We demonstrate a high-quality double-layer antireflection coating for high index (n=2.61at 514 nm) photorefractive and electro-optic bismuth silicon oxide(Bi12SiO20)crystals. The antireflection coating comprises two electron-beam-deposited quarter-wave dielectric layers ofMgF2andZrO2,and increases the beam throughput by as much as 20&percent; per interface at normal incidence. For holographic recording applications, the antireflection coating eliminates multiple internal reflections that produce extraneous gratings. The combination of these two factors significantly increases the diffraction efficiency and the two-beam coupling gain. Key characteristics of the double-layer coating include a broadband minimum that encompasses typical write and read wavelengths forBi12SiO20with normal-incidence reflectivities of less than 0.2&percent; at 514 nm and 1&percent; at 633 nm, respectively, and a forgiving angular dispersion for both TE and TM polarized waves with reflectivities of less than 2&percent; for angles of incidence up to 45°. ©1997 American Institute of Physics.