Effects of polarization evolutions inside the cholesteric liquid crystal cell on the output characteristics of ring type fiber lasers

Among the liquid crystal devices, the cholesteric liquid crystals (CLC) are known to have interesting optical properties because of their peculiar molecular structures, through which the overall displacement of an optical beam traces out a helical path. When an unpolarized light is incident at the CLC cells, one of the circular polarizations whose electric vectors are rotating along the helical path of layers is almost transmitted and the other one rotating in the opposite direction is almost reflected if the wavelength of incident light is in multiples of the rotation pitch. We report experimentally observed and theoretically analyzed output characteristics of fiber lasers with the CLC cell inserted as a polarization device into the fiber cavity.