| With the development of commercial design software and ion assisted deposition, multilayer dispersive mirrors, such as Gires-Tournois mirrors or chirped mirrors, play a crucial role in ultra-fast laser system by providing precise dispersion compensation. Nevertheless, precise knowledge of its group-delay (GD) as well as group delay dispersion (GDD), which is the first and second derivative of the optical phase delay with respect to the angular frequency ω respectively, though necessary for manufacturing and characterization of this device, is still a tough task. In this thesis, a novel white-light Michelson interferometric scanning system is proposed based on the summary of former testing systems. Our system employs a fiber-optic spectrometer to record interferometric information while a picomotor is appended to drive the sample arm to scan the coherent extent. With the research on the methods of extracting phase information from the interferometric data, we promoted frequency-domain methods and time-domain methods such as Windowed Fourier Transform, Wavelet Transform. Maximum Seeking Method and Phase-locking Method. The methods built for the precise extraction of Group Delay and Group Delay Dispersion had been verified by the simulation and experiments. The main contents of the thesis are mainly arranged as three sections:1. Testing system of phase properties of dispersion compensation mirrors. A novel white-light Michelson interferometric scanning system is built. Compared with former experimental facility, some new features are appended in our system to decrease the testing error and improve the stability of system. A software which can control the movement of picomotor and data save of fiber spectrometer is made for the storage of scanning interferometric data. Moreover, the repeatability and stability of the testing system has been evaluated based on the measurement of the errors caused by white-light source, fiber-optic spectrometer and beam splitter.2. Extraction of phase properties of dispersion compensation mirrors from single shot interferogram data. Two methods about determination of phase and GD including Windowed Fourier Transform and Wavelet Transform based on single shot interferogram are discussed in this thesis. It can be concluded from numerical simulations of the Windowed Fourier transform method that the proposed method can obtain phase information of thin films correctly and quickly. A series of experiments are carried out for the measurement of dispersion compensation mirrors (including chirped mirror and Gires-Tournois cavity resonator) using our novel white-light interferometric system. Compared with the dispersion curves given by Spectra Physics, the accuracy of our method and stability of our system are verified.3. Extraction of phase properties of dispersion compensation mirrors from scanning interferometric spectrum data. To overcome the shortcomings and limitations of former methods, a two-dimension time domain scanning method is proposed to retrieve the GD directly, which can avoid the error amplifying effect brought by derivation and increase the testing accuracy of group delay dispersion (GDD). Combining seeking optimal function for interferogram maximas and phase-lock tracing method, two novel time-domain algorithms are presented which enables the direct extraction of group delay and thus obtains a remarkable decrease of noise level in group delay and group delay dispersion. A home-made Gires-Tournois cavity is measured by the above methods. With the comparison between the measured group delay and group delay dispersion with the design ones, the results demonstrate the higher testing accuracy and good repeatability of our system over a broad spectral range. |
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