<title>Observation of optical fibers by near-field microscopies: effects of aging</title>

Study and comparison of two polishing methods for platinum–iridium surfaces, by means of three characterization techniques

“…The SNOM with shear-force regulation (see figure 3) that we use is able to detect two different signals, which are the near-field optical signal and the interaction forces between the probe and sample surface, well known as the shear-force interaction. The shear-force regulation is used to obtain the topography of the surface while the probe (an optical fibre), detects the optical near-field close to the surface to provide an image of the optical intensity distribution [13]. The shear-force method is used to keep the probe tip in the nearfield of the object at a constant distance from the surface and to avoid contact between the tip and the sample surface during the scanning [17,[29][30][31].…”

“…The shift distance τ is given in numbers of intervals (τ = n , where 1 n N − 1). The resulting two-dimensional PSD γ (ν x , ν y ) is given (as a function of spatial frequencies) by [12,13]…”

“…In particular, the contamination phenomena depend on the surface quality of the mass standard. Interest in microscopic studies of surface quality [6][7][8][9][10][11][12][13][14][15] of a mass has grown, as it is well known that surface roughness is a factor in determining the long-term stability of mass standards.…”

“…In order to compare the efficiency between two polishing techniques in terms of surface quality, the BIPM provided a platinum-iridium disc (90% platinum and 10% iridium), one side of which was polished directly on a lathe by means of a diamond tool and the other side was polished using diamond paste. The two sides of the disc were characterized by means of three methods: scanning nearfield optical microscopy (SNOM) [13,15] with shear-force regulation [17]; with the optical roughness-meter based on angle-resolved scattering (ARS) theory [18] and with an x-ray reflectometer [19]. The first technique simultaneously provides topographical properties (topographic image) of the sample surface and optical properties (optical image) obtained by the probe (optical fibre) in the near-field of the surface.…”

“…One of these surfaces was afterward treated by a manual polishing using diamond paste. Three characterization instruments were chosen to measure surface roughness: Scanning Near field Optical Microscope (SNOM) with shear force regulation, optical roughnessmeter and X-ray Reflectometer [6][7][8][9][10][11][12][13]. The two latter are based on angle resolved scattering (ARS) theory.…”