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 SiO2, a low-refractive-index material (n=1.23), as well as dense SiO2(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 SiO2 are R_int|TE = 99.9% and R_int|TM = 98.9%, respectively, indicating the high potential of the ODRs for low-loss waveguide structures.
© 2005 Optical Society of America
J.-Q. Xi, Manas Ojha, Woojin Cho, J. L. Plawsky, W. N. Gill, Th. Gessmann, and E. F. Schubert, "Omnidirectional reflector using nanoporous SiO2 as a low-refractive-index material," Opt. Lett. 30, 1518-1520 (2005)