A broadband antireflection coating for enhanced holographic recording and readout in bismuth silicon oxide

We demonstrate a high-quality double-layer antireflection coating for high index (n = 2.61 at 514 nm) photorefractive and electro-optic bismuth silicon oxide (Bi₁₂SiO₂₀) crystals. The antireflection coating comprises two electron-beam-deposited quarter-wave dielectric layers of MgF₂ 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 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 for Bi₁₂SiO₂₀ with normal-incidence reflectivities of less than 0.2% at 514 nm and 1% at 633 nm, respectively, and a forgiving angular dispersion for both TE and TM polarized waves with reflectivities of less than 2% for angles of incidence up to 45°. © 1997 American Institute of Physics

Post-growth tuning of inverted cavity InGaAs/AlGaAs spatial light modulators using phase compensating dielectric mirrors

A novel method is demonstrated for the correction of cavity thickness deviations imposed by technological limitations in the growth process of a resonant cavity spatial light modulator. This method is based on cavity phase compensation through the use of an externally-deposited dielectric Bragg mirror and provides an effective means of optimizing the device characteristics. In particular, such mirrors can significantly relax otherwise stringent epitaxial growth requirements in the fabrication of hybrid silicon/compound-semiconductor spatial light modulators incorporating Fabry-Perot cavities. We further demonstrate deposition of a conductive, index-tunable indium tin oxide (ITO) antireflection coating that is designed to maximize the contrast ratio and throughput of the inverted-cavity modulator configuration.© 1995 American Institute of Physics