ABSTRACT
A differential profilometry technique is adapted to the problem of measuring the roughness of hollow glass fibres by use of immersion objectives and index-matching liquid. The technique can achieve picometer level sensitivity. Cross validation with AFM measurements is obtained through use of vitreous silica step calibration samples. Measurements on the inner surfaces of fibre-sized glass capillaries drawn from high purity suprasil F300 tubes show a sub-nanometer roughness, and the roughness power spectrum measured in the range [5 · 10(-3) m(-1) 10(-1) m(-1)] is consistent with the description of the glass surface as a superposition of frozen capillary waves. The surface roughness spectrum of two capillary tubes of differing compositions can be quantitatively distinguished.
Subject(s)
Glass/chemistry , Interferometry/instrumentation , Ions , Silicon Dioxide/chemistry , Surface PropertiesABSTRACT
Guided mode resonance filters (GMRFs) are a promising new generation of reflective narrow band filters, that combine structural simplicity with high efficiency. However their intrinsic poor angular tolerance and huge area limit their use in real life applications. Cavity-resonator-integrated guided-mode resonance filters (CRIGFs) are a new class of reflective narrow band filters. They offer in theory narrow-band high-reflectivity with a much smaller footprint than GMRF. Here we demonstrate that for tightly focused incident beams adapted to the CRIGF size, we can obtain simultaneously high spectral selecitivity, high reflectivity, high angular acceptance with large alignment tolerances. We demonstrate experimentally reflectivity above 74%, angular acceptance greater than ±4.2° for a narrow-band (1.4 nm wide at 847 nm) CRIGF.
