Meskers Arjan J H, Spronck Jo W, Schmidt Robert H Munnig
Opt Lett. 2014 Apr 1;39(7):1949-52. doi: 10.1364/OL.39.001949.
Periodic nonlinearity (PNL) in displacement interferometers is a systematic error source that limits measurement accuracy. The PNL of coaxial heterodyne interferometers is highly influenced by the polarization state and orientation of the source frequencies. In this Letter, we investigate this error source and discuss two interferometer designs, designed at TU Delft, that showed very low levels of PNL when subjected to any polarization state and/or polarization orientation. In the experiments, quarter-wave plates (qwps) and half-wave plates (hwps) were used to manipulate the polarization state and polarization orientation, respectively. Results from a commercial coaxial system showed first-order PNL exceeding 10 nm (together with higher order PNL) when the system ceased operation at around ±15° hwp rotation or ±20° qwp rotation. The two "Delft interferometers," however, continued operation beyond these maxima and obtained first-order PNLs in the order of several picometers, without showing higher order PNLs. The major advantage of these interferometers, beside their high linearity, is that they can be fully fiber coupled and thus allow for a modular system buildup.
位移干涉仪中的周期性非线性（PNL）是一种限制测量精度的系统误差源。同轴外差干涉仪的PNL受源频率的偏振态和方向影响很大。在本信函中，我们研究了这种误差源，并讨论了代尔夫特理工大学设计的两种干涉仪，这两种干涉仪在任何偏振态和/或偏振方向下都表现出非常低的PNL水平。在实验中，分别使用四分之一波片（qwps）和半波片（hwps）来控制偏振态和偏振方向。当商业同轴系统在hwp旋转约±15°或qwp旋转约±20°时停止运行时，其结果显示一阶PNL超过10 nm（以及更高阶的PNL）。然而，这两种“代尔夫特干涉仪”在超过这些最大值后仍能继续运行，并获得了几皮米量级的一阶PNL，且未显示出更高阶的PNL。这些干涉仪的主要优点除了具有高线性度外，还在于它们可以完全光纤耦合，从而实现模块化系统构建。
