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用交流电场代替直流电场来驱动液晶光折变器件能够克服直流电场带来的动态散射、永久光栅、电解等效应,这些对于器件的实用是非常不利的。利用二波耦合方法在无偏置正弦交流电场作用下研究了掺C60的向列液晶中记录的光折变光栅的形成及其相干放大应用。实验中在交流电场作用下于通常的、掺C60的向列液晶盒中观察到了稳定的非对称能量转移,并获得了和直流电场下相比拟的、大的光束耦合比,从而证明在交流电场下液晶薄膜中记录的光栅是由光致空间电荷场作用下的液晶分子重新取向而形成的。利用上述强的光束耦合比实现了交流电场作用下的相干放大实验,并在小的输入光强下取得了190 cm-1的增益。
Replacing the direct current electric field with an alternating electric field to drive the liquid crystal photorefractive device can overcome the dynamic scattering, permanent grating and electrolysis effects caused by the direct electric field, which are very unfavorable to the practical use of the device. Two-wave coupling method was used to study the formation of photorefractive grating recorded in C60-doped nematic liquid crystals and its coherent amplification under unbiased sinusoidal AC electric field. In the experiment, stable asymmetric energy transfer was observed in the usual C60-doped nematic liquid crystal cell under the action of AC electric field and a large beam coupling ratio was obtained under the DC electric field, which proves that in the AC electric field The lower grating recorded in the liquid crystal film is formed by the reorientation of the liquid crystal molecules under the action of the photo space charge field. The coherent amplification experiment under AC electric field was realized by using the above strong beam coupling ratio, and a gain of 190 cm-1 was achieved with a small input light intensity.