Engineering Phonon Wave Properties for Thermally Efficient LEDs: Tracing and Tailoring Phase of Acoustic Phonons

The phonon wave manipulations in thermal engineering are still scarce, where the ability to trace and tailor its phase could enable a wide range of applications. Even though the relationship between generation mechanisms and phase has been known for decades, the acoustic (AC) phonon phase information was obscured by the dynamic interference behavior of propagating wavepackets. Here, we present a new type of phase detection scheme of AC phonons where the tensile and compressive strains are distinguished and the entire phononic spectrum is imposed in nonlinear photoelastic regime. The vertical electric field along the symmetry axis of LEDs, in this way, could tune the initial phase of AC phonons. From the time-domain analysis, we further clarify the relationship between the phase and anharmonic phononic scatterings. This work in combination with our previous works on modal manipulations [1] and nanoscale thermal characterization [2,3] could be useful in understanding detailed pictures of AC heat carriers toward the wavemechanical thermal managements.

[1] H. Jeong et al., Phys. Rev. Lett. 114, 043603 (2015).
[2] H. Zhang et al., Nano Letters 16, 1643 (2016).
[3] T. Kim et al., APL Materials 5, 086105 (2017).