Center for Correlated Electron Systems

Seminar

Time-resolved Spectral Interferometry for phase change measurement

September 1, 2016l Hit 1030
Date : September 8, 2016 17:00 ~ 18:30
Speaker : Dr. Tsogvoo Khosochir((Chonbuk National University))
Location : Bldg. 19, Rm. 210
In this work, the spectral phase changes of materials have been studied in their stationary states and in the non-equilibrium states. The non-equilibrium states were invoked by the laser pulses. To study the phase changes, three different interferometer setups were built. The details of building those interferometers were described and the working principles of the interferometers were explained.
 First part is the introduction about the chromatic refractive index of a material and its influence on the phase change of light passing through the material. Second part is dedicated to a method for measuring the phase changes of the spectral components of a white light beam. A Fourier transform white light interferometer was built. Using the setup were measured the spectral phase and retardation of transparent optical materials such as BK7 glass and wave plates. The spectral phase change information of BK7 glass was measured and compared to the theoretical estimation and the results of other method. The retardation of a quarter wave plate was measured and compared to the measurement of a conventional method.
 Third part is about the measurement of the phase information of the ultrashort laser pulse. The time duration of the pulse was approximately 10 femptosecond. A SPIDER (spectral phase interferometry for direct electric field reconstruction) setup was built to characterize the pulse phase.
 Last part is about the influence of the material on the phase change of the ultrashort laser pulse. To do this, a time-resolved spectral interferometry method was developed. Merge of the spectral integrated pump-probe method and cross-correlation interferogram between the incident (reference) and transmitted (probe) pulse through the sample yields spectral resolved pump probe method, which extracts the spectral resolved amplitude and phase information of the pulse passing through the sample. A 0.5 mm-thick ZnSe crystal was used as sample. Significant change was observed in the spectral phase information due to the pump pulse irradiation on the sample. Also the spectral phase change was measured by spectral interferometry to avoid phase fluctuation of pulse. An intriguing change in spectral phase (specially group dispersion and third order dispersion) was observed nearby “0” time delay between the pump and probe pulses.