Volume 77, Issue 8, August 2006
Index of content:
- THERMOMETRY; THERMAL DIFFUSIVITY; ACOUSTIC; PHOTOTHERMAL AND PHOTOACOUSTIC
Signal analysis and characterization of experimental setup for the transient thermoreflectance technique77(2006); http://dx.doi.org/10.1063/1.2336187View Description Hide Description
The transient thermoreflectance (TTR) technique is a powerful optical pump-probe technique often used to measurethermal properties and monitor ultrafast processes. The technique has been used to measure a range of properties including the thermal conductivities of thin films and electron-phonon coupling factors to mention a few. TTR measurements are sensitive to residual heating and misalignment, which can lead to erroneous analysis of TTR data. To minimize these errors, we have developed a simple phase correction technique to reduce errors associated with residual heating and other background noise. Besides its simple implementation, the technique also requires no previous knowledge of the transient reflectance response. The technique is verified with simulated experimental data. The importance of proper alignment of the pump and probe beams over the entire range of pump-probe time delays of interest is discussed, along with a means of quantifying error associated with misalignment.
77(2006); http://dx.doi.org/10.1063/1.2336771View Description Hide Description
An ultrasonic interferometric sensor has been introduced for the measurement of subtle changes in the physical properties of fluids such as density, viscosity, and bulk modulus. Tone burst ultrasonicwaves are generated using a single peizocrystal bonded in between two solid delay line media of slightly different lengths. One side is in contact with a reference fluid (with known properties) and the other with a fluid whose properties are to be measured. The ultrasonicwaves reflect from the two solid-fluid boundaries and are received back by the peizocrystal where the interference effects are measured. The longitudinal waves were used to measure the longitudinal impedance, while shear waves were used to measure the shear impedance. Glycerin-water mixtures were used as the test material. A simple plane wave model was shown to provide satisfactory comparison with experiments. Various parameters that influence the measurement were studied.