Z. Karim et al., A BROAD-BAND ANTIREFLECTION COATING FOR ENHANCED HOLOGRAPHIC RECORDING AND READOUT IN BISMUTH SILICON-OXIDE, Applied physics letters, 70(21), 1997, pp. 2793-2795
We demonstrate a high-quality double-layer antireflection coating for
high index (n = 2.61 at 514 nm) photorefractive and electro-optic bism
uth silicon oxide (Bi12SiO20) crystals. The antireflection coating com
prises two electron-beam-deposited quarter-wave dielectric lavers of M
gF2 and ZrO2, and increases the beam throughput by as much as 20% per
interface at normal incidence. For holographic recording applications,
the antireflection coating eliminates multiple internal reflections t
hat produce extraneous gratings. The combination of these two factors
significantly increases the diffraction efficiency and the two-beam co
upling gain. Key characteristics of the double-layer coating include a
broadband minimum that encompasses typical write and read wavelengths
for Bi12SiO20 With normal-incidence reflectivities of less than 0.2%
at 514 nm and 1% at 633 nm, respectively, and a forgiving angular disp
ersion for both TE and TM polarized waves with reflectivities of less
than 2% for angles of incidence up to 45 degrees. (C) 1997 American In
stitute of Physics.