Interferometry polarization modulation

PDI-FT-VCD spectrometers is somewhat below that of PEM-FT-VCD spectrometers in the region where they have been directly compared, the mid-IR region. Recently, an FT-VCD instrument was described that possessed both PDI capability and conventional polarization-modulation capability using a PEM. Referred to as double polarization modulation interferometry, this technique offers advantages of signal... 

Polavarapu PL (1997) Double Polarization modulation interferometry. Applied Spectroscopy 51 770-777. 

Fundamentals. A beam of monochromatic light is polarized and split into two beams. One beam passes an optical medium, e.g. the electrolyte solution in an electrochemical cell close to the solution/electrode interface. After passage it interferes with the other beam for a review of two-beam interferometry see [915, 916]. This technique was limited both with respect to spatial resolution and sensitivity for further details, see [917]. Temporal or spatial modulation of the reference beam enabled the use of very thin cells (i.e. the sensitivity was increased) and the two-dimensional reconstruction of concentration maps. 

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