Near-field scanning optical microscope(NSOM) has been studied as a promising tool for high density optical recording which cannot be achieved with far field optics. But for the practical use, there exist some problems to be solved such as the low recording speed caused by the low optical power of NSOM probes and the difficulty of fine positioning on storage media.
To remove the first bottle neck, we suggest a new optical probe to produce high optical power and investigate its optical and thermal characteristics. This high-power tip can handle the record-high optical power of > 150mW injected into the fiber core. This tip has a unique thick heat-conducting metal layer deposited through an electroplating process. The sub-wavelength aperture of the tip is fabricated by the controlled lapping of the end face with in-situ optical monitoring. With some recording experiments on phase change and photo-resist media we verify the new probe is useful as high-power light emitting sources for optical storage devices.
Furthermore, studying the nature of light loss mechanisms in metal-coated NSOM probes and investigating various kinds of fabricated probes, we find a way how to improve the transmission efficiency of probes. As results, in the region of the large diameter (> λ/2n), the light power decreases proportionally to the square of the probe-radius as the geometrical ray tracing prospects. In the final taper of the small diameter(< λ/2n), the light power decays very fast as the waveguide theory expects. The NSOM prove can have the transmission efficiency of above 1 % with the aperture diameter of $\frac{\lambda}{10}$ if the taper angle is smaller at the middle taper but larger at the final taper than those of existing NSOM probes.
For fine positioning of probes, we propose an optical means to readout the position signal from the optical disc, of which the performance is verified through simulations and experiments.
