Omnidirectional reflector using nanoporous ${\mathrm{SiO}}_2$ as a low-refractive-index material

Abstract

Triple-layer omnidirectional reflectors (ODRs) consisting of a semiconductor, a quarter-wavelength transparent dielectric layer, and a metal have high reflectivities for all angles of incidence. Internal ODRs (ambient material’s refractive index $n⪢1.0$) are demonstrated that incorporate nanoporous ${\mathrm{SiO}}_2$, a low-refractive-index material $(n=1.23)$, as well as dense ${\mathrm{SiO}}_2$ $(n=1.46)$. GaP and Ag serve as the semiconductor and the metal layer, respectively. Reflectivity measurements, including angular dependence, are presented. Calculated angle-integrated TE and TM reflectivities for ODRs employing nanoporous ${\mathrm{SiO}}_2$ are ${R_{\mathrm{int}}\mid }_{\mathrm{TE}}=99.9\%$ and ${R_{\mathrm{int}}\mid }_{\mathrm{TM}}=98.9\%$, respectively, indicating the high potential of the ODRs for low-loss waveguide structures.

© 2005 Optical Society of America