介质层充电对光栅光调制器驱动的影响

利用高斯定理分析了二氧化硅层中存在电荷时，光栅光调制器中的空间电场分布，得到了光栅光调制器在介质层存贮电荷影响下的静电力公式. 分析了调制器中二氧化硅介质的充电和放电机理，得到了光栅的位移随介质充放电的变化关系. 通过分析指出当驱动电压的周期和介质的充放电时间常数相近的时候，介质层中存贮的电荷会使得可动光栅被下拉后发生缓慢的回跳. 电压被撤消后，光栅会受到存贮电荷所产生电场的作用而被下拉. 当驱动电压的周期远小于介质的充放电时间常数的时候，随着存贮电荷的增加，光栅在有外加电场时被下拉的距离和外加电场为零时被下拉的距离逐渐相等，光调制器输出光的光强变化逐渐减弱，当存贮电荷产生的电场为外加电场的一半时，器件完全失效. 通过实验对理论分析的结果进行了验证，实验结果和理论分析一致. 文章最后提出了一种消除介质层所存贮的电荷的方法，通过实验证明了这种方法的可行性. 关键词： 微机电系统 光栅光调制器 介质层充电

Effect of dielectric charging on gating light modulator

Electric field distribution of the light modulator affected by the dioxide dielectric charging is deduced with Gauss law. Electrostatic force formula of the movable grating under such condition is obtained. Charging and discharging mechanisms of the dielectric have been analyzed. The relationship between movable grating's displacement and the dielectric charge is obtained. The results show that the grating will bounce back and then be pulled down when it is actuated by low frequency voltage. When the actuating voltage period is far shorter than the charging time constant, variation of the modulator's output light intensity will be increasingly small until the modulator is disabled thoroughly when the field produced by the storage charges is half that of the actuating electric field. Experiment was carried out to test the theoretical analysis and the results agree well. Finally, a method is proposed to eliminate the storage charge, and its feasibility is proved by the experiment.