Spatial distribution and polarization dependence of the optical near‐field in a silicon microfabricated probe

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Abstract
This paper reports on the spatial distribution and polarization behaviour of the optical near‐field at the aperture of a Si micromachined probe. A sub‐100 nm aperture at the apex of a SiO2 tip on a Si cantilever was successfully fabricated by selective etching of the SiO2 tip in a buffered‐HF solution using a thin Cr film as a mask. The aperture, 10–100 nm in size, can be reproducibly fabricated by optimizing the etching time. The optical throughput of several apertures was measured. For a 100 nm aperture, a throughput of 1% was approved. The probe shows a very high optical throughput owing to the geometrical structure of the tip. The spatial distribution of the near‐field light is measured and simulated using a finite difference‐time domain method. The polarization behaviour of apertures with different shapes was analysed using a photon counting camera system.