The electromagnetic field incident on the thin-film layers in a solid immersion lens (SIL) system is decomposed into contributions from homogeneous and inhomogeneous waves, which are commonly referred to as propagating and evanescent waves, respectively. The homogeneous and the inhomogeneous parts have different properties with respect to the field distribution in the gap and inside the recording layers. The homogeneous part is shown to diffract like a focused wave with a numerical aperture of 1, and the inhomogeneous part decays exponentially away from the bottom of the SIL. Two examples are discussed in detail, and the concept of a vector illumination system transfer function, which includes effects of the recording layers, is introduced.
A pupil plane filtering technique is applied to data signal
detection in an optical data storage system that uses a solid
immersion lens (SIL) and a quadrilayer phase change recording
medium. Two systems that have the effective numerical aperture
(NAEFF) of 1.1 and 2.0 are investigated. A new
filter is designed for the NAEFF=2.0 system on the
basis of this study. We have confirmed by numerical calculations
that the technique improves signal contrast, which is defined by
the ratio of the difference signal to the sum signal between the
homogeneous crystalline area and the homogeneous amorphous area.
We have also confirmed that the technique makes the contrast less
sensitive to the gap width between the SIL and the recording
medium. The vectorial feature of the light is considered in the
calculations. The calculated irradiance distributions and signal
levels for the system with NAEFF =1.1 are confirmed
by experiments.
A pupil-plane filtering technique is applied to data-signal detection in an optical data-storage system that uses a solid immersion lens (SIL) and a four-layered phase-change recording medium. We have confirmed by numerical calculations and experiment that the technique improves signal contrast and makes the contrast less sensitive to the gap width between the bottom surface of the SIL and the top surface of the recording medium. Light that is incident upon the objective lens that is used with the SIL is linearly polarized, and the full vectorial feature of the light is considered in the calculations.
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