Measurement of period of interference patterns with sub-micron period

Measurement of period of interference pattern is desirable, while tuning the mirror interferometer for changing photo-written Bragg wavelengths during inscription of fiber Bragg gratings. The article presents the application of simple method, which uses a single lens, for the on-line measurement of the period of interference pattern with sub-micron wide period along with experimental results. Sub-micron period interference fringes are created using a mirror–beam splitter combination and biprism and a source at visible wavelengths. Analysis of experiments on magnifying, recording and measurement of period of these interference patterns using a CCD camera are presented and results are discussed. Its extension to magnifying and recording of sub-micron period fringes in UV region is discussed.