We have worked out the diffraction pattern in the phase-grating mode of a cholesteric liquid crystal (cholesteric) with a pitch gradient. The pitch gradients considered are symmetric and asymmetric with respect to the sample center. For a uniform input beam, the intensity profile of each diffraction order becomes broad. Further, in the symmetric gradient, the profile of each order is irregular, while in the asymmetric gradient it is nearly flat. For a Gaussian input beam, for the symmetrically deformed structure the profile for each order is asymmetric, while for the asymmetrically deformed structure, the profiles just becomes broad. We find that even a 5% nonuniformity in the pitch can drastically alter the diffraction profiles.
© 2002 Optical Society of America
(050.1950) Diffraction and gratings : Diffraction gratings
(160.3710) Materials : Liquid crystals
(230.1950) Optical devices : Diffraction gratings
(230.3720) Optical devices : Liquid-crystal devices
M. S. Giridhar, K. A. Suresh, and G. S. Ranganath, "Optical diffraction in nonuniform cholesteric liquid crystals: phase-grating mode," J. Opt. Soc. Am. A 19, 19-23 (2002)