Surface emitting lasers for optical near-field data storage

One of interesting applications of two dimensional VCSEL arrays is high density optical data storage. We proposed a micro-metal aperture VCSEL for producing optical near-field. The evanescent wave emitted from a small metal aperture formed on a VCSEL surface is irradiated to an optical disk, such as a phase change optical disk. We carried out a near-field analysis on the radiation from the metal micro aperture loaded on a VCSEL by using 2-dimensional finite element method (FEM), showing a possibility of a spot size of below 100 nm. We can recycle the reflected wave from the metal aperture, when we properly design the phase matching between the DBR mirror and the metal. We can expect an improvement in a power conversion efficiency of radiating near field light from the aperture by using a "photon recycling" effect. An expected efficiency and power density are discussed for 850 nm metal aperture VCSELs. We have fabricated micro-metal aperture VCSELs by using focus ion beam etching. The size of the fabricated apertures ranges from 100 nm and 400 nm. We have realized sub-mA low threshold metal aperture VCSELs. The power density is estimated to be similar to 6 kW/cm(2). We will be able to improve the power density by reducing the oxide aperture in the cavity. We also discuss on another way to increase the efficiency and the power density, such as using a surface plasmon effect of a small metal tip formed on the surface. We will discuss a possibility of optical near-field recording by using the proposed metal aperture VCSEL.