We proposed a microaperture vertical-cavity surface-emitting laser (VCSEL) with metal grating for the enhancement of optical near-field induced by surface plasmon resonance. We carried out the two-dimensional modeling on the near-field intensity at a microaperture surrounded by a grating in a silver film. An increase in throughput through the microaperture was obtained by the control of a surface plasmon mode, which is strongly dependent on some structural parameters of the grating, such as the period and the depth of a grating, and so on. We also fabricated a microaperture VCSEL with concentric circular grating, exhibiting a large enhancement in peak intensity. The intensity is eight times larger than that of a single-aperture device without grating.

We propose a double-aperture structure to enhance the optical near-field in metal nanoaperture vertical-cavity surface-emitting lasers (VCSELs). We fabricated 850 nm GaAs VCSELs with subwavelength-sized double metal apertures closed to each other. The optical near-field localized in the metal apertures is strongly enhanced by the excitation of localized plasmon around the metal apertures. The far-field power radiated from the apertures is enhanced to be 16 times larger than that from a single aperture VCSEL. The peak power density is as large as 2.5 mW/μm2 with a spot size of 260 nm. The obtained power density is even larger than that of a conventional single-mode VCSEL without nanoapertures, which is very encouraging for use in high-density data storages.

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We demonstrate a metal nano-aperture GaAs vertical cavity surface emitting laser (VCSEL) for sub-wavelength optical near-filed probing, which exhibits the strong plasmon enhancement of both optical near-fields and voltage signals with forming a metal nano-particle in the nano-aperture. The threshold current is as low as 300microA, which shows a potential of nano-probing with low power consumption. We achieved the first demonstration of a plasmon enhanced VCSEL near-field probe. The spatial resolutions of the VCSEL probe with 400 nm and 200 nm apertures are 240nm and 130 nm, respectively. The enhancement factors of the optical near-field and voltage signal with a Au particle are 1.8 and 2, respectively. Our FDTD simulation shows that localized plasmon with a Au particle is very helpful for increasing optical near-field intensity and signal voltage in the VCSEL nano-probing.

We experimentally demonstrated the amplification of optical disk readout signals by homodyne detection. This technique uses optical interference to amplify the signals. We further applied phase-diversity detection to reliably obtain the amplified readout signal. The optical system was carefully designed so that a sufficiently amplified readout signal can be obtained. In particular, we applied a corner cube prism as a reflection mirror to achieve sufficient stability of the interferometric optical system. We experimentally demonstrated a 3.6 times amplification of a Blu-ray Disc readout signal. The estimated signal-to-noise ratio (SNR) improvement for an assumed eight-layer optical disk readout signals by applying homodyne detection on the basis of the observed amplification was +7.9 dB, which significantly enables reliable readout of recorded signals. The present technique will be essential for the real commercialization of next-generation multilayer optical disk because of its outstanding ability of SNR improvement.

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