制作光纤光栅用相位掩模的衍射行为研究

Study of diffraction action of phase mask for optical fiber grating fabrication

利用严格耦合波理论对用于光纤光栅制作的相位掩模的衍射特性进行了深入的研究。研究发现，在紫外写入波长（248nm）下，为了使零级衍射效率〈5％，且±1级的衍射效率〉35％，相位掩模的刻槽深度必须控制在230．280nm。占宽比必须控制在0．48～0．65。同时，与标量衍射理论的结果进行了分析对比。这些都为相位掩模的实际制作提供了有意义的结果。

The diffraction characteristics of the phase mask for fiber grating fabrication is investigated using rigorous coupled-wave theory. The results show that in order to keep the zero order diffraction efficiency 〈5% and ±1st order diffraction efficiency 〉35% at UV-written wavelength of 248 nm, the groove depth and duty cycle of the mask must be controlled within the range of 230 - 280 nm and 0.48 - 0.65 respectively. This conclusion has been analyzed and compared with that based on scalar diffraction theory. Useful information has been resulted for the practical fabrication of the phase mask.