Observation of 3-D Birefringence Distribution of Polymer Thin Film by Near-Field Optical Microscope

Abstract

Abstract. According to development of optical engineering, the measurement accuracy of optical components and materials has become more important. For example, birefringence in polymer thin film is an essential issue for development of liquid crystal display. In this study, after a PVA (poly vinyl alcohol) film was embedded by photopolymer and cut by ultramicrotome, a cross-sectional birefringence distribution of cut film was observed by birefringence contrast scanning near-field optical microscopy (B-SNOM). As a result, three dimensional birefringence ratios were calculated and birefringence of parallel to stretching direction was larger than that of vertical one. This result shows that cross-sectional birefringence distribution is yielded by inhomogeneous distribution of molecular alignment in film material according to asymmetry stretching.

Effect of mechanical treatments on orientation behavior and spectral properties of azoderivative dyes incorporated in poly(vinyl alcohol) films

“…When the polymer films are subjected to mechanical stretching, additional birefringence is produced. [ 13 ] The birefringence evaluation is carried out based on optical compensators, channeled spectral microscopy, or other methods.…”

Determination of local refractive index variations in thin films by heterodyne interferometric scanning near-field optical microscopy

“…12 In another manner, the three-dimensional birefringence distribution of a polymer thin film was characterized by combining a heterodyne interferometric detection with a SNOM. 13 Those reported setups, although using near-field techniques, did not yield nanometric lateral resolutions. Alternative methods based on near-field ellipsometry were proposed to assess local inhomogeneities 14 and local refractive indices of ultrathin films ͑with a thickness of several nanometers͒.…”