Evaluation and alignment of Ronchi phase gratings in the lateral shearing interferometer at 193nm wavelength

Abstract

Thesis (M.S.)--University of Rochester. Institute of Optics, 2004. Missing page vi.The Lateral Shearing Interferometer (LSI) with two Ronchi phase gratings is an ideal tool to measure optical systems at deep ultraviolet (DUV) light. The geometry and construction of the LSI circumvent the tight constraints needed in conventional dual path interferometers, such as the Twyman-Green interferometer and others. Light sources at DUV have short temporal coherence lengths, thus hindering conventional interferometers from operating at DUV light. This constraint is eliminated by the geometry of the LSI, since it exploits the spatial coherence properties of the DUV light sources. The LSI offers many benefits over dual path interferometers because the LSI is self referencing, compact, and resilient to mechanical vibrations. Other factors like matching the intensity, the polarization, and the dispersion of DUV light do not interfere with the ability of the LSI to measure the wavefront, unlike in the conventional dual path interferometers. This makes the LSI a superior interferometer to be used with DUV light over the other systems. The thesis deals with the theory, the choice of materials, the tolerance of Ronchi phase gratings, and the construction and alignment of the LSI at 193nm wavelength. The evaluation of the optical properties of the Ronchi phase gratings and their mechanical alignment in the LSI is the primary focus of this thesis. If the optical properties of the gratings are not quantified and the mechanical alignment of the gratings is not precisely executed, the LSI will not be operational. From the evaluation of the data obtained from the gratings and the modeling of the mechanical alignment of the gratings, the resolution of the LSI was calculated to be λ/25 at 193nm wavelength