Photon-phonon collaboratively pumped laser

Abstract In 1916, Einstein considered stimulated photon emission of electron radiation, offering the theoretical foundation for laser1, technically achieved in 19602. To date, the laser has been emerging as cutting-edge modern technology from fundamental research to daily life3-8. However, the byproduct thermal phonons, along with heat creation of ineluctable non-radiative transition, is ineffective, even playing a detrimental role in lasing process. Despite the powerful ability of phonons, e.g., Raman process9,10 or Cooper pairs in superconductors11,12, it seems impractical to use random thermal phonons to help a highly coherent laser generation far beyond the inherent fluorescence spectra. Here, we realize a photon-phonon collaboratively pumped laser enhanced by heat in a counterintuitive way. We observe a clear laser transition from phonon-free 1064 nm lasing to phonon-pumped 1176 nm lasing in Nd:YVO4 crystals, associated with the phonon-pumped electron population inversion under gradually increasing temperature. Moreover, an additional temperature threshold (Tth) appears as the trigger besides ordinary photon pump power threshold (Pth). A two-dimensional lasing phase diagram of parameter space is revealed and experimentally verified with a general threshold curve ruled by Pth = C/Tth (constant C upon loss for a given crystal), similar to Curie’s Law13. We anticipate our strategy will promote the study of laser physics via dimension extending, searching for ultrahigh-efficiency and low-threshold yet tunable and compact laser devices via this new temperature degree of freedom.