Measuring concave diffraction grating efficiencies at grazing incidence.
Measuring concave diffraction grating efficiencies at grazing incidence.
复制标题
DOI：
10.1364/ao.16.003171
复制
发表时间：
1977-12
期刊：
影响因子：
1.9
通讯作者：
W. R. Hunter;Dianne K. Prinz
中科院分区：
文献类型：
--
作者：
W. R. Hunter;Dianne K. Prinz
通过测量衍射光束和入射光束的强度并取它们的比值，可以得到给定阶数的凹面衍射光栅的效率。有效的测量要求入射光束和衍射光束都被检测器完全收集。然而，在掠入射时，衍射光束可能由于像差而扩散超出检测器。此外，连续级的衍射光束可能重叠，使得不能进行明确的效率测量。对于海军研究实验室使用的测量仪器的几何形状，利用光线追迹法研究了象差对效率测量的影响。该仪器是一种反射计，其中检测器以给定的距离围绕光栅旋转，该仪器连接到一个VUV单色器，该单色器反射发散光束。像差对这种仪器的主要影响是衍射光束在色散方向上的扩展。衍射光束的宽度取决于波长，并且在水平焦点处最小，扩展到更长和更短的波长。减小入射光束的发散度减小了扩展，但是对于小半径光栅，并不总是足以使得整个衍射光束可以被检测器收集。也可以调整从检测器到光栅的距离，以帮助收集所有衍射光束。将介绍射线追踪研究的一些结果，并讨论入射光束的f数和探测器距离的影响。
The efficiency of a concave diffraction grating in a given order is obtained by measuring the intensities of the diffracted and incident beams and taking their ratio. A valid measurement requires that both the incident and diffracted beams be collected, in their entirety, by the detector. At grazing incidence, however, the diffracted beam may spread beyond the detector due to aberrations. In addition, the diffracted beams of consecutive orders may overlap so that unambiguous efficiency measurements cannot be made. The effect of aberrations on efficiency measurements has been studied, using ray tracing, for the geometry of the measuring instrument in use at the Naval Research Laboratory. This instrument, a reflectometer wherein the detector rotates around the grating at a given distance, is attached to a VUV monochromator which furnishes a diverging beam. The main effect of aberrations for this instrument is a spread of the diffracted beam in the direction of dispersion. The width of the diffracted beam is wavelength dependent and is minimal at the horizontal focus, spreading to longer and shorter wavelengths. Reducing the divergence of the incident beam reduces the spread but, for small radius gratings, not always sufficiently so that the entire diffracted beam can be collected by the detector. The distance from the detector to the grating can also be adjusted to aid in collecting all the diffracted beam. Some results of the ray tracing studies will be presented, and the effect of the f-number of the incident beam and the detector distance will be discussed.