(Color online) (a) Schematic diagram of the experimental setup. (b) Measured ice film thickness as a function of time at . The solid (red) line is obtained from the white light reflectance spectrum and the circles (blue) are obtained by laser picosecond acoustics.
Simulation of the longitudinal ultrasonic strain propagation in an ice film at assuming thermoelastic generation in YBCO in the absence of diffusion processes. The frequency dependence of the ultrasonic attenuation in the ice film is taken into account. The horizontal axis is in the direction, and the zero of this axis is at the YBCO-ice boundary (at ).
(Color online) Relative reflectivity changes as a function of delay time: (a) for ice films at of thicknesses of 129 and on an YBCO film and (b) for the bare YBCO film at . The solid (red) lines represent experimental data and the dashed (blue) lines are theoretical fits.
(Color online) Density plot of for the ice film growth at over a period of : (a) experiment and (b) theoretical simulation.
(Color online) Phase lead of the oscillations in reflectivity at (with respect to a sine variation with the origin at , just after the time of arrival of the acoustic pulse at the YBCO-ice interface). The solid (red) line represents the experimental data whereas the dotted (purple), dashed (green), and dashed-dotted (blue) lines represent theoretical fits for three different values of the refractive index of the ice film (holding the parameters and constant). The best agreement is obtained when .
Relative reflectivity change obtained when water is introduced into the vacuum chamber intentionally to form ice. These data correspond to an ice film thickness of at a temperature of .
Physical constants for ice and YBCO. The definitions of the symbols are as follows: is the longitudinal sound velocity, is the mass density, is the specific heat capacity, is the complex refractive index, is the optical wavelength, is the optical absorption depth, and are photoelastic constants, and is the coefficient involved in the ultrasonic attenuation that varies quadratically with the acoustic frequency . The symbols , , , and refer to the pump light, whereas , , , and refer to the probe light. The density and longitudinal sound velocity for YBCO at both 110 and are taken to be equal to those quoted in Ref. 18 at .
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