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Static Tester for Characterization of Optical Near-Field Coupling Phenomena

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We present an experimental set-up for systematical studies of optical near-field coupling phenomena using a solid immersion lens SIL to surpass the conventional far field diffraction limit. The set-up incorporates a microscope objective lens with NA0.80 in combination with a hemispherical SIL manufactured from glass with refractive index n1.887 and a laser with a wavelength of 430 nm. Test samples are positioned within the evanescent decay distance from the bottom surface of the SIL using a closed-loop-controlled piezo actuator. The laser spot can be scanned over the sample enabling a study of the push-pull signal of pregrooved samples on a split photodiode. The intensity distribution and polarisation state of the light reflected from the sample in the exit pupil of the microscope objective lens is studied on a CCD camera. The reflected light can be combined with a reference beam into an interferogram used for alignment purposes. We present measurements of evanescent coupling of light to a glass sample and the push-pull signal of a reflective phase grating with a groove pitch of 300 run as a function of thickness of the air gap between de SIL and the sample. The evanescent coupling to a glass sample can accurately be described by thin-film optics theory. Experiments show that the push-pull signal amplitude depends on the polarisation state of the irradiating beam.

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  • Computer Systems

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