90°反射式相位延迟器的设计

铜蒸气激光反射镜在非正入射的时候 ,两个不同的偏振态之间会产生不同的相移。通过优化设计 ,在4 90～ 5 30nm之间p、s波获得了 90°的相移 ,同时也使反射率在 99 998%以上。Ag层的厚度对于相移不敏感 ,并且当其厚度大于一定值的时候 ,对反射率没有影响。根据误差分析 ,制备薄膜时其沉积速率精度控制在± 1%以下 ,在光谱范围内能达到± 15 2 8°的相移误差 ,相移均在 5 0 4nm处附近存在有一个收敛值。折射率的变化控制在± 1%以下 ,在光谱范围内能达到± 12 77°的相移误差。最外一层厚度变化± 1% ,其相移变化达到± 5 5°,2～ 5层和 9～ 16层对相移的影响也在 0 .5°之上 ,其余各层对相移影响非常的小。使用时的入射角控制在± 1°时 ,在光谱范围内能达到± 2 .86°的相移误差。在 5 30nm附近的波段对入射角不敏感。

Design of 90° Reflection-Induced Phase Retarder

When copper vapour laser mirror is used at an abnormal incidence the different phase shift of the polarization states may occurred. An optimum technique has been used to determine the layer thickness for a coating design that produce a 90° phase shift between the p- and s-polarization components over 490～530 nm while the average reflectivity is above 99.998%. The thickness of Ag layer is insensitive to the phase shift. There is no effect on the transmittance when the thickness is larger than a constant. A tolerance analysis indicates that the deposition rate should be controlled within ±1% to achieve ±15.28° phase shift error, with a convergence of the phase shift about 504 nm. The phase shift error could reach ±12.77° within ±1% of the refractive index variation over the designed wavelength range. The variation of the outmost layer's thickness also is controlled within ±1% to achieve ±5.5°, and the phase shift error caused by the layers from 2 to 5 and 9 to 16 is above ±0.5°, but the other film layers have little influence on the phase shift. The incidence angle also is controlled within ±1% to achieve ±2.86° phase shift error over the designed wavelength range, the waveband around 530 nm is insensitive to the incident angle.