Physical Optics Analysis of a Fiber-Delivered Displacement Interferometer

Optical interferometry has been used for over a century for precision metrology. Advances in interferometry, such as the inclusion of a laser source, have increased the precision of such interferometers. In this thesis, we examine a fiber-fed, heterodyne, spatially separated, differential wavefront interferometer. The combination of technology in this interferometer can allow easier and more robust alignment of the system, reduce the complexity, and increase the precision. Heterodyne interferometry has been examined in great depth, and was not the primary focus of this research, but rather a tool that we will utilize. The primary focus of this thesis is to examine the effects that the fibers will have on the system, as well as what types of fibers are more suitable for this fiberfed system. Additionally, we will investigate the physics of a spatially separated, differential wavefront interferometer. Fibers can facilitate an easier alignment of metrology systems because they will remain aligned if they are perturbed, unlike systems that are fed via free-space optics. Additionally, the alignment of the source is decoupled from the actual interferometer, which allows any faults in the alignment of either to be immediately reduced to the actual source. Unfortunately, fibers can also introduce problems into a heterodyne interferometer. The first is phase shifts due to any physical or optical length change of the fibers. These changes can be due to the fiber either moving, being subjected to an external stress, changing in temperature, or any number of environmental perturbations. Since heterodyne interferometers