Abstract: Gratings etched into polyimde thin layers are used to align nematic liquid crystals. The gratings are prepared by illumination of a 1.1 micrometer period phase mask with a KrF excimer laser at 248 nm. Fluences of 87 mJ cm$+$MIN@2$/ and 128 mJ cm$+$MIN@2$/ with one and two shots were used to ablate the gratings. Modelling of the fluence distribution behind the phase mask predicts a grating period equal to that of the phase mask and this is found experimentally. The amplitudes of the gratings are obtained from diffraction using a HeNe laser and are between 100 nm and 150 nm deep. The alignment layers are used in twisted nematic cells and the azimuthal anchoring energy is measured as a function of grating fabrication conditions. Anchoring energies of the order of 10$+$MIN@5$/ J m$+$MIN@2$/ are found in agreement with the Berreman theory. !17
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机译：摘要：蚀刻到聚酰亚胺薄层中的光栅用于对准向列液晶。通过用248 nm的KrF准分子激光照射1.1微米周期的相位掩模来制备光栅。用一两次枪的87 mJ cm $ + $ MIN @ 2 $ /和128 mJ cm $ + MIN @ 2 $ /的通量烧蚀光栅。对相位掩膜后面的注量分布进行建模可预测出等于相位掩膜的光栅周期，这是通过实验发现的。光栅的振幅是通过使用HeNe激光进行衍射获得的，深度在100 nm至150 nm之间。对准层用于扭曲向列单元中，并且根据光栅制造条件来测量方位锚固能量。大约10 $ + $ MIN @ 5 $ / J m $ + $ MIN @ 2 $ /的锚定能量与Berreman理论一致。 ！17
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