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We quantitatively analysed the factors contributing to the optical transmission enhancement of a sub-wavelength Sb thin film lens, using the finite-difference time-domain (FDTD) method. The results show that the transmission enhancement of the dielectric with a Gaussian distributed refractive index loaded in a sub-wavelength circular hole is not only due to the high refractive index dielectric, but also due to the specific distributions of refractive index. It is the first study about the effects of the refractive index distribution on the transmission of a sub-wavelength aperture. This kind of lens has practical applications in the very small aperture lasers and for near-field optical storage and lithography. [ABSTRACT FROM AUTHOR]

AgInTeSbGe thin films were deposited by the de sputtering method, Due to germanium doping in the AgInTeSb film, new Ag2Te and Ge2Sb2Te5 crystalline phases were formed, The crystallization temperature and the activation energy of the AgInTeSbGe thin film increased manifestly with the addition of Ge. The refractive index n and the extinction coefficient k of the AgInTeSbGe film in the amorphous and crystalline states were measured. The reflectivity contrast of the AgInTeSbGe phase-change optical disk was greater than %30 in almost the whole visible region. A minimum recording mark of about 220 nm in length was recorded using the AgInTeSbGe thin film as the recording medium. The reflectivity contrast of the minimum recording mark was about %25. [ABSTRACT FROM AUTHOR]