The study of frequency-scan photothermal reflectance technique for thermal diffusivity measurement

Abstract

A frequency scan photothermal reflectance technique to measure thermal diffusivity of bulk samples is studied in this manuscript. Similar to general photothermal reflectance methods, an intensity-modulated heating laser and a constant intensity probe laser are used to determine the surface temperature response under sinusoidal heating. The approach involves fixing the distance between the heating and probe laser spots, recording the phase lag of reflected probe laser intensity with respect to the heating laser frequency modulation, and extracting thermal diffusivity using the phase lag-(frequency)(1/2) relation. The experimental validation is performed on three samples (SiO2, CaF2, and Ge), which have a wide range of thermal diffusivities. The measured thermal diffusivity values agree closely with the literature values. Compared to the commonly used spatial scan method, the experimental setup and operation of the frequency scan method are simplified, and the uncertainty level is equal to or smaller than that of the spatial scan method.

Structured illumination with thermal imaging (SI-TI): A dynamically reconfigurable metrology for parallelized thermal transport characterization

“…43 Note that dR dT is nearly constant from 300-400 K for gold, which is used as the transducer layer in our experiments below. 44 We note the distinction between optical techniques based fundamentally on single-point TR thermometry, such as thermal metrology using TDTR, FDTR and photothermal/thermal wave microscopy, all of which rely on a monolithic photodetector, 25,26,30,31,45,46 and techniques using large-field (kilopixel to megapixel) TR imaging. The latter has been used for temperature mapping of microelectronics, 47,48 with some extension to the 1D heat transfer characterization of thin films and nanowires using Joule heating, or composites with a single-point-type laser pumpprobe method.…”

Z-scanning laser photoreflectance as a tool for characterization of electronic transport properties

“…(Note that due to the open aperture configuration, the measurement noise remains roughly constant as the microscope objective is stepped through focus. This mitigates the competition between sensitivity and signal to noise encountered in offset pump-probe techniques [30].) On the other hand, the strong 3D limit may not be attainable due to the spatial resolution (as determined by the value of ω 2 p + ω 2 o ).…”

“…This has prevented the industrial use of such transverse scanning techniques to date. An alternative suggestion involves holding the pump-probe offset fixed and recording the LPR phase with respect to the modulation frequency [30], since the LPR signal will also depend on modulation frequency due the dependence of diffusion length on modulation frequency [27]. However, the determination of the optimal pump-probe offset for this type of measurement remains an empirical challenge.…”

Thermophysical properties of thin fibers via photothermal quantum dot fluorescence spectral shape-based thermometry

“…These frequency domain lifetime measurement were coupled with a fast fourier transform (FFT) and intensity-modulated light source to induce fluorescence in a fiber optic-based temperature sensor [14], thereby improving the detected signal and aiding in fitting the lifetime decay as a function of temperature. However, for frequency domain modulated heating experiments (such as lock-in IR thermometry [15] or modulated optical reflectance [16]), the probe beam is usually continuously illuminating and the pump beam is modulated. The current study seeks to use quantum dot fluorescence thermometry as a method to probe the modulated surface temperature of fibers.…”