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Photo-control of molecular orientation of polymer
materials is of great interest for the development of highly
functionalized holographic optical devices.
In this study published in AZojomo*, by Hiroshi Ono
and Nobuhiro Kawatsuki from Nagaoka University of Technology and
University of Hyogo, optical phase gratings were fabricated from
photo-crosslinkable polymer liquid crystals with mesogenic
4-(4-methoxycinnamoyloxy)biphenyl side groups by irradiating with 325
nm interference lights and subsequent annealing at elevated
temperatures. Recorded phase gratings were verified after the
annealing process, although no gratings were observed immediately
after the exposure. The characteristics of the phase gratings were
strongly dependent on the polarization states of the two recording
beams, and the resultant gratings involve not only linear
birefringence caused by the reorientation of the mesogenic groups but
also surface relief modulation generated by the molecular migration.
Diffraction measurement and AFM observation
revealed that the intensity holographic gratings involve both linear
birefringence and surface relief, while the pure polarization gratings
without surface topological relief were formed for the polarization
holographic recordings.
It is anticipated that these unique phenomena of
the material and phase grating can be applicable to various kinds of
optical devices. |
