Schematic drawing of the time-resolved ellipsometer. P: polarizer; W: wave-plate; A: analyzer; S: slit; D: silicon photodiode. The inset shows a magnified view of the sample.
Optical model for the effect of the propagation of an acoustic pulse on the ellipsometry parameters and . The geometry of the model is shown as the inset to panel (a). Data in panel (a) are the simulation result as a function of the propagation distance of the acoustic pulse, ; and are the ellipsometry parameters in the absence of the acoustic pulse. Panel (b) shows a comparison between the changes in calculated directly from the model (solid line) and the changes in derived indirectly (filled symbols) by the simulation of our measurement.
The acoustic signal from the Au film measured at short time is used as an input to simulate the acoustic wave that enters water. The inset shows the geometry of a simulation model: three acoustic pulses are modeled as three layers in water with corresponding distances and proportional values of the index of refraction.
Comparison of measured and simulated phase of the acoustic wave in time-resolved ellipsometry for a Au film in contact with water. Changes in are plotted against delay time between pump and probe optical pulses.
Sensitivity of time-resolved ellipsometry calculated at time zero using the same conditions as described in Fig. 2. An inverse dependence of , which is probe power change induced by the pump pulses normalized by the total power incident on the photodiode, is predicted with respect to off-null angle. The arrow indicates the off-null angle of ≈5° selected for typical experiments and 45° used for the method based on a polarizing beamsplitter.
The experimental quantity , at the off-null angle denoted in Fig. 5, is plotted against delay time for water. Also plotted in this panel are the pump-probe signals measured using and polarized light at the same angle of incidence, as would be done in a typical measurement by picosecond interferometry.
Time-resolved ellipsometry measured in various gases, both simple (Ar, , , and He) and complex (the refrigerant R134a), at atmospheric pressure. (a) Relative phase angle plotted against delay time in ns. Each data set is shifted vertically by from the data for He. (b) Representative fits to the Ar data, and the contribution of each exponential and damped oscillation part are plotted.
Comparison to the reference values measured at 11 MHz. The absorption and dispersion of sound waves, obtained from Fig. 7 using the model described in the text, are compared to data from Refs. 26 and 27 for Ar (squares), (circles), and (crosses).
Fitting parameters at Au/gas interfaces.
Parameters for the calculation of Fig. 8 at 331 K (Refs. 28 and 29).
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