When a nematic liquid crystal layer is brought in contact with a photosensitive polymer, on which a holographic grating is recorded by two laser beams with opposite circular polarization, due to a spatial modulation of the direction of the local optical axis, the photopolymer modulates the anchoring conditions for NLC in a similar way. As a result, a similar grating is induced in NLC with the enhanced diffraction efficiency and specific diffraction properties controlled by electric field.(6) Here we show that, even in the case of a typical finite value of the anchoring energy, the numerical modeling confirms the characteristic asymmetric diffraction of the circularly polarized reconstructing beam and exchange by energy between the zero and first-order diffracted beams. Some other properties, such as reduced diffraction efficiency, appearance of higher diffraction orders and too-large optical phase retardation of a nematic cell at the areas occupied by gratings, can also be modeled by assuming some corrugation of the surface.
A nematic replica of a holographic polarization grating: Modeling of the ideal and a corrugated surface
2006
Abstract
When a nematic liquid crystal layer is brought in contact with a photosensitive polymer, on which a holographic grating is recorded by two laser beams with opposite circular polarization, due to a spatial modulation of the direction of the local optical axis, the photopolymer modulates the anchoring conditions for NLC in a similar way. As a result, a similar grating is induced in NLC with the enhanced diffraction efficiency and specific diffraction properties controlled by electric field.(6) Here we show that, even in the case of a typical finite value of the anchoring energy, the numerical modeling confirms the characteristic asymmetric diffraction of the circularly polarized reconstructing beam and exchange by energy between the zero and first-order diffracted beams. Some other properties, such as reduced diffraction efficiency, appearance of higher diffraction orders and too-large optical phase retardation of a nematic cell at the areas occupied by gratings, can also be modeled by assuming some corrugation of the surface.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
