飞秒激光刻划铌酸锂实现极化反转的实验研究

Experimental Study of Electric-Field Poling in LiNbO_3 Crystal by Femtosecond Laser Carving

采用飞秒激光加工制作周期性极化铌酸锂(PPLN)。实验中利用飞秒激光加工机的高精密加工的特性,在晶体+Z面刻划出周期性条纹,条纹周期以及深宽比可调,并加均匀的高压电场,通过改变晶体表面形状来影响晶体内部电场分布。实验观察到沿飞秒激光刻划方向有明显的极化现象,以及加工参量对极化反转的影响。该方案比纳秒激光刻划精度高,影响区小,可以做到更高深宽比且保持刻槽规则的形状。直接用激光刻划,无需掩模和光刻工艺,具有较大的灵活性,作为改进制作周期性极化铌酸锂的可选方案,更适合做各种新型器件。

A novel technique of periodically poling in femtosecond laser treated LiNbO3 （LN） crystal is reported. Because of the precision of the femtosecond laser machine, the width and depth of snicks can be controlled exactly. Then the high voltage electric field was operated on ＋ Z side of the LiNbO3 crystal. The visible poling pattern was observed by microscope. The machining parameter influence on the electric-field poling distributing in the crystal was investigated. Comparing with nanosecond laser carving, using femtosecond laser pulses the structure can be made more precisely with a larger deep-width ratio. The new technique does not need expensive and complicated mask and lithography, and periods of periodically poled lithium niobate （PPLN） can be adjusted flexibly. Although the mechanism of core formation is not clear yet, it would be a very useful technique in developing new type of periodically poled devices.