Infrared interferometric systems using a CO₂ laser operating at a wavelength of 10.6 μm have been investigated. The purpose of infrared interferometry is to test (1) optical components required for high energy laser systems such as infrared transmitting materials and diamond-turned metal mirrors, (2) unpolished rough surface optics during the early stages of fabrication, and (3) deep aspherics and other optics of nonconventional surface figures. The physical principles behind longer wavelength interferometry are as follows. First, the specular component of scattered light increases with increasing wavelength for randomly rough surfaces. Second, the aspheric departure from the best fit reference sphere (in units of probing wavelength) is reduced. This reduced sensitivity gives us a manageable number of fringes in the interferogram of deep aspherics. Specific systems developed in this work are the infrared laser unequal path interferometer (IRLUPI), the IRLUPI with infrared computer generated hologram (IRCGH), the infrared common path interferometers such as the infrared point diffraction interferometer (IRPDI), and the infrared scatterplate interferometer (IRSPI). The above interferometers produce interferograms of equal optical path difference (OPD). Other types of common path interferometers which provide interferograms of differential OPD (or slope) are also developed. They are the infrared lateral shearing interferometers (IRLSI); a germanium plane parallel plate, the Ronchi ruling, and the double grating lateral shearing interferometer. A pyroelectric vidicon (PEV) has been employed as an AC infrared detector with proper intensity modulation techniques. Chopping, panning, and phase variation of the interferogram modulate the interference pattern effectively for various types of interferometers. Germanium and zinc selenide optics are used for lenses and beamsplitters. A He-Ne gas laser is installed parallel to the CO₂ beam for the ease of initial alignment. Many test interferograms are shown using each interferometer. The statistical analysis and experimental verification of the relationship between fringe contrast and rms surface roughness enabled us to have noncontact measurement of surface roughness interferometrically. This result was used for a series of tests for the unpolished large diameter off-axis parabolic mirror during the preliminary fabrication stage. Some interesting topics are included for future investigation to fulfill the growing demand for versatility in interferometry.

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An interferometric method for measuring the total dispersion of short lengths of optical single mode fiber has been demonstrated. An analysis of the system in terms of linear system theory has also been carried out. The experiments were performed using a multimode GaAlAs semiconductor laser to measure the total dispersion of a borosilicate single mode optical fiber at a wavelength of approximately .873 μm. The experiments were conducted using various combinations of laser spectral width and fiber length. Changing the drive current to the laser enabled its spectral width to be varied from 2.3 nm to 5.8 nm FWHM. The fiber length was varied from approximately 0.2 m to 1.0 m. An analysis was also carried out to explain the effects on the interferograms of the unequal mode spacing of the multimode GaAlAs laser. Two methods of approximating the amount of variation of the laser mode spacing were also developed based on analysis of the interferograms. Analysis of the auto-correlation interferogram allowed the GaAlAs laser spectral width to be determined. This data was then used to compute a cross-correlation interferogram and then compared with the measured cross-correlation interferogram. The value of the fiber dispersion used in calculating the cross-correlation interferogram was varied until the computed interferogram agreed with the measured interferogram, this determined the value of the dispersion for the fiber that was used in that experiment. The experimentally determined value of the total dispersion of the single mode optical fiber used in these experiments agreed very well with published results.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2005. / Dr. Steven Liang, Committee Member ; Dr. Thomas R. Kurfess, Committee Chair ; Dr. Shreyes Melkote, Committee Member.

This dissertation is an experimental study of a novel type of interferometry based on the generation of Second Harmonic (SH) light. In this work interferometers are described in which an interference pattern arises when two SH waves are superimposed. These waves come from doubling the fundamental frequency of a laser by means of non-linear crystals. Three interferometers are described that have different applications according to their sensitivity to detect wavefront distortions. One interferometer has low sensitivity and is useful in the contouring of refractive objects that produce large wavefront distortions of the order of hundreds of visible wavelengths. The other two interferometers have high sensitivity and one of them is capable of detecting wavefront distortions as small as 1/20 of wavelength. Special emphasis is placed on development of the first interferometer which is a real-time, common-path, self-referencing interferometer that yields interferograms in the visible. The interferometer is based on the fact that a SH wavefront generated under PM conditions is a faithful replica of the laser wavefront. The two interfering SH wavefronts are produced one before and the other after the object under study, and by virtue of its chromatism, they are very slightly different. Consequently, very low density fringes are produced upon their superposition. In this application, noncritically phase matched crystals perform best, and we have found that Y-cut LiNbO₃ crystals configured for surface acousto-optic applications are very convenient. The conversion efficiencies are very low (of the order of 10⁻⁵) consequently optical damage to the LiNbO₃ due to the SH is no problem. The crystals are phase matched by controlling their temperature and are used with a repetitively pulsed Nd:Yag laser operating at 1.06 μm. The chief limitations of this interferometer come from practical considerations in imaging objects with high spatial frequencies that reduce the contrast of the interferograms. The high sensitivity interferometers make use of the changes of phase and amplitude induced in the SH wavefront by the phase mismatch of angle tuned crystals to provide information. The interferometers are directly sensitive to small wavefront tilts and do not require additional reference wavefronts.

The culmination of a comprehensive experimental study of a number of nonlinear optical materials and their device applications. The optical phenomenology surrounding the interaction of laser radiation with these materials is emphasized. In addition to using interferometric techniques for their investigation and application, the overall theme of the research is the incorporation of interferometric descriptions of these interactions. Interference is commonly regarded to be the domain of linear optics; this work invalidates that notion. Nonlinear optics (NLO) is presented as simply a natural extension of linear optics. After a complete introduction to the general theory and relevant concepts required in the field of NLO, the first half of this manuscript presents a number of studies concerned with second-order nonlinear crystals for laser frequency conversion. The second half of this dissertation presents research on the nonlinear optical properties of semiconductors and semiconductor microstructures for optical-bistability-related applications. Optical bistability and related phenomena made possible using these materials in a nonlinear Fabry-Perot interferometer are stressed.

Thesis (M. Sc.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references (p. 85-88). Also available via the World Wide Web.

Thesis (M. Sc.)--University of Canterbury, 2006. / Typescript (photocopy). Includes bibliographical references (p. 109-111). Also available via the World Wide Web.

Thesis (Ph. D.)--University of Oregon, 2006. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 113-116). Also available for download via the World Wide Web; free to University of Oregon users.

Algorithms for analyzing laser interferometry signals were developed and adopted to the computer based processing of small displacement measurements. These methods, matrix operation approach and fixed parameters approach, are based on signal phase calculation and are able to replace complex fringe counting electronic circuits. The matrix operation provides an approach for instantaneously displaying the results. The computer fixed parameters analysis allows the laser intensity to vary arbitrarily during a measurement. Displacement caused by a piezoelectric crystal was measured. Second order polynomial curve fitting was performed. The root mean square error is found to be 0.0086 μm in this 8-bit data acquisition system. CTEs of a fused silica plate and a tube were measured by an interferometry system. Signals were analyzed by both manual chart approach and computer based fixed parameters approach. Results agree well with published data. The accuracy of the CTE measurement system was 4 μ€, one third of the reference NBS SRM 739 suggested standard deviation. Out-of-plane and in-plane displacements can be measured independently from speckle interferometry. Their resolutions are 0.3164 μm/cycle for the out-of-plane configuration and 0.224 μm/cycle for the in-plane configuration with light incident angle of 45°. Optical systems with Fast Fourier Transform data analysis showed that the minimum detectable vibration amplitudes were 0.0065 μm, 0.0038 μm, and 0.0010 μm for the out-of-plane speckle, the in-plane speckle, and Michelson interferometry systems respectively. Resonance frequency of a steel rod was found by the optical non-contact sensing system. The modulus of elasticity calculated from the resonance frequency was close to the literature data, 182 GPa vs. 200 GPa. / Graduation date: 1992