Photon-phonon collaboratively pumped laser

In 1917, Einstein considered stimulated photon emission of electron radiation, offering the theoretical foundation for laser, technically achieved in 1960. However, thermal phonons along with heat creation of non-radiative transition, are ineffective, even playing a detrimental role in lasing efficiency. Here, we realize a photon-phonon collaboratively pumped laser enhanced by heat in a counterintuitive way. We observe a laser transition from phonon-free 1064 nm lasing to phonon-pumped 1176 nm lasing in Nd:YVO₄ crystal, associated with the phonon-pumped population inversion under high temperatures. Moreover, an additional temperature threshold (T_th) appears besides the photon-pump power threshold (P_th), and a two-dimensional lasing phase diagram is verified with a general relation ruled by P_th = C/T_th (constant C upon loss for a given crystal), similar to Curie's Law. Our strategy will promote the study of laser physics via dimension extension, searching for highly efficient and low-threshold laser devices via this temperature degree of freedom.