FABRICATION OF MULTI-WAVELENGTH LIGHT SOURCES

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An ultra-high density optical memory using optical near field is attracting much interest for future Tera byte optical data storage. Various optical near field sources have been reported. A common important issue of near field optical sources is to realize high output power density for recording data. Goto proposed a Tera byte optical memory system using a vertical cavity surface emitting laser (VCSEL) array. This optical memory system is based on an optical head consisting of a two-dimensional VCSEL array with low total power consumption.We have proposed a micro-aperture vertical cavity surface emitting laser (VCSEL) for use in near field optical data storage. We carried out the near-field analysis of micro-aperture VCSEL using 2-dimensional finite element method. We calculated the distribution of optical near field generated near a micro-aperture, and showed that the spot size is potentially smaller than 100 nm, which is less than wavelength by a factor of 8. We fabricated a VCSEL loaded by a Au film on the top surface for blocking the emitting light and formed a sub-wavelength size aperture using focused ion beam (FIB) etch through this film. Single mode operation was obtained for a micro-aperture VCSEL with 3 μm square active region. The differential quantum efficiency was increased by a factor of 3 in comparison with that before forming a 400 nm square aperture. We estimated the power density of light radiated from a 400 nm square aperture to be 0.17 mW/ m2. In addition, we measured the near field distribution of a 200 nm square VCSEL by using a scanning near field microscope.In addition, We propose the use of a micro-aperture surface emitting laser (VCSEL) for near-field optical probing. We present the first demonstration of two-dimensional imaging by using the voltage change signal from a micro-aperture VCSEL induced by the interaction with a probe.