Heat transport in GaAs membranes studied by using a GaAs MEMS thermal sensor

We propose a novel method for performing phonon spectroscopy of the heat transport process in micro-scale structures. We illuminate a GaAs MEMS suspended beam structure with two light pulses from a femtosecond (fs) laser. The generated phonons by the laser pulses propagate through the GaAs beam, and interfere with each other. We measure the phonon interference signal as the temperature rise on the beam by measuring the frequency shift of the MEMS resonator. By performing a Fourier transform for the interference signal, we will obtain the phononic spectrum of the heat transport process. Our preliminary result shows that the temperature rise increases when the two laser pulses have a zero time-delay, which is a typical feature of the phonon interference. The proposed method is promising for realizing the ultra-fast phonon spectroscopy of heat transport process.