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The spectral characteristics of long-period gratings (LPGs) have been researched over the last two decades, and many sensing applications of LPGs have been proposed due to their spectral sensitivity to many surrounding environmental parameters such as the temperature, pressure, and refractive index. However, this sensitivity to many parameters can also be a curse due to cross-sensitivity and the inability to distinguish which environmental parameter is responsible for the LPG’s spectral behavior. For the application proposed here—monitoring the progress of a resin flow front, its velocity, and the permeability of the reinforcement mats during the infusion stage of resin transfer molding—the multi-sensitivity of LPGs is a distinct advantage, as it provides the ability to monitor the mold environment at various stages of manufacturing.

It has been established that the polarization properties of light can be effectively utilized in modifying the characteristic of the imaging system. As a matter of fact, the diffraction properties of the lens get modified when it is masked by polarizing devices. It is therefore well expected that characteristics of an imaging system also be modified by utilizing polarization properties of light. This calls for a systematic study of the effects of variation of polarization on diffraction pattern of different kinds of slit including polarizing devices. In this paper we study the Fraunhofer diffraction pattern of a slit using polarized light having variable state of polarization across it.

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