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将一种可旋转的双棱镜引入到相位掩模技术中以改变光栅的写入Bragg波长.在该系统中,光纤光栅是由来自可旋转双棱镜所形成的波长为248nm的紫外干涉条纹写入的,其中,相位掩模被用作1级衍射光的分束器,通过双棱镜的旋转可改变两写入光束的交叉角.为了初始化Bragg波长的参考值,双光栅的顶角由相位掩模的1级衍射角和双棱镜的折射率确定.因为在～100nm范围内两光束的非对称旋转对光栅周期的改变是5×10-4nm,双棱镜引入的光栅的闪耀可忽略.当Bragg波长的移位为1nm时,棱镜最大的旋转角为～1degree,最小的旋转角是～2.4min.与Talbot干涉仪中平面镜的旋转角～23s/nm相比,该相位干涉仪中棱镜的旋转精度降低了2～3个数量级.
A rotatable dichroic prism is introduced into the phase mask technique to change the write Bragg wavelength of the grating In this system, the fiber grating is written by UV interference fringes with a wavelength of 248 nm formed by a rotatable biprism , Where the phase mask is used as the beam splitter for the first order diffracted beam and the crossing angle of the two written beams can be changed by the rotation of the biprism.In order to initialize the reference value of the Bragg wavelength, Mode 1 diffraction angle and the refractive index of the biprism.Because the asymmetric rotation of the two beams in the ~ 100 nm range changes the grating period by 5 × 10 -4 nm, the grating introduced by the biprism shines negligible When Bragg When the wavelength shift is 1 nm, the maximum rotation angle of the prism is ~ 1 degree and the minimum rotation angle is ~ 2.4 min. The rotation of the prism in the phase interferometer compared to the rotation angle of the flat mirror in the Talbot interferometer ~ 23 s / nm Accuracy reduced by 2 to 3 orders of magnitude.