phononlasing

Phonon lasing, also known as a SASER (sound amplification by stimulated emission of radiation), is the generation of a coherent beam of phonons by stimulated emission, analogous to a laser emitting photons. In a phonon laser, a medium with an inverted population of vibrational states provides gain for a selected acoustic mode in a high-Q resonator or waveguide.

Operation relies on population inversion of vibrational levels, achieved by optical or electrical pumping. When the inverted medium interacts with the resonant phonon mode, stimulated emission adds phonons coherently, overcoming intrinsic losses and giving rise to a coherent, narrow-band acoustic field. The device typically exhibits a threshold pump and a linewidth narrower than the resonator mode.

Platforms for phonon lasing include optomechanical systems in which a driven optical cavity stimulates a mechanical mode, semiconductor nanostructures with strong electron-phonon coupling, and surface-acoustic-wave devices that amplify coherent surface acoustic waves. Experimental realizations have demonstrated coherent phonon generation and sustained mechanical oscillations at gigahertz to terahertz frequencies in nanoscale resonators and integrated circuits.

Potential applications span high-resolution spectroscopy, on-chip signal processing, quantum information processing, and precision sensing, where coherent phonons can serve as carriers of information or as probes of material properties. Phonon lasing thus links concepts from laser physics to nanoscale acoustics, enabling on-demand, coherent control of vibrational energy.