In the context of non-equilibrium statistical mechanics, the TCLE method (a method in which the admittance of a system is directly calculated from time-convolutionless equations with external driving terms) for the linear response, is formulated in terms of thermo-field dynamics and in this way, thermo-field dynamics is generalized to the case of a quantal system interacting with its surroundings and with an external driving field. It is applied to interacting boson systems, and an admittance formula for such systems is derived using the TCLE method.In the context of non-equilibrium statistical mechanics, the TCLE method (a method in which the admittance of a system is directly calculated from time-convolutionless equations with external driving terms) for the linear response, is formulated in terms of thermo-field dynamics and in this way, thermo-field dynamics is generalized to the case of a quantal system interacting with its surroundings and with an external driving field. It is applied to interacting boson systems, and an admittance formula for such systems is derived using the TCLE method.

Progress of Theoretical PhysicsNov 1, 20057 citations

Intrinsic thermo-optical feedback as a fundamental nonlinear interaction in rare-earth-doped systems

Rodrigo F. Silva, José dos Santos, Emanuel Pinheiro Santos +5 more

Intrinsic heating is generally regarded as a secondary consequence of optical excitation in rare-earth (RE $^{3+}$ )-doped materials. Here, we demonstrate that intrinsic thermo-optical feedback can drive the transient dynamics of optically excited RE $^{3+}$ systems. To isolate this mechanism, we develop a minimal coupled population-temperature model that describes the interplay among optical excitation, temperature-dependent non-radiative relaxation, heat generation, and thermal dissipation. The model predicts the emergence of a threshold excitation power associated with intrinsic thermo-optical feedback, giving rise to pronounced slowing down of the transient dynamics, non-monotonic evolution of the characteristic transient time, population overshoot, and accelerated relaxation above threshold. These phenomena originate from the progressive establishment of a positive feedback loop linking temperature, non-radiative relaxation, quantum efficiency, and heat generation. Our results demonstrate that temperature should no longer be regarded merely as a passive external parameter, but rather as an active dynamical variable capable of continuously reshaping the relaxation pathways of the system. More broadly, this work establishes intrinsic thermo-optical feedback as a general framework for understanding nonlinear transient phenomena in optically excited RE $^{3+}$ materials and provides a complementary perspective for interpreting threshold-like optical responses beyond conventional photon-avalanche mechanisms.Intrinsic heating is generally regarded as a secondary consequence of optical excitation in rare-earth (RE$^{3+}$)-doped materials. Here, we demonstrate that intrinsic thermo-optical feedback can drive the transient dynamics of optically excited RE$^{3+}$ systems. To isolate this mechanism, we develop a minimal coupled population-temperature model that describes the interplay among optical excitation, temperature-dependent non-radiative relaxation, heat generation, and thermal dissipation. The model predicts the emergence of a threshold excitation power associated with intrinsic thermo-optical feedback, giving rise to pronounced slowing down of the transient dynamics, non-monotonic evolution of the characteristic transient time, population overshoot, and accelerated relaxation above threshold. These phenomena originate from the progressive establishment of a positive feedback loop linking temperature, non-radiative relaxation, quantum efficiency, and heat generation. Our results demonstrate that temperature should no longer be regarded merely as a passive external parameter, but rather as an active dynamical variable capable of continuously reshaping the relaxation pathways of the system. More broadly, this work establishes intrinsic thermo-optical feedback as a general framework for understanding nonlinear transient phenomena in optically excited RE$^{3+}$ materials and provides a complementary perspective for interpreting threshold-like optical responses beyond conventional photon-avalanche mechanisms.

Journal of LuminescenceAug 29, 20260 citations

Intrinsic heating is generally regarded as a secondary consequence of optical excitation in rare-earth (RE

^{3+}

)-doped materials. Here, we demonstrate that intrinsic thermo-optical feedback can drive the transient dynamics of optically excited RE

^{3+}

systems. To isolate this mechanism, we develop a minimal coupled population-temperature model that describes the interplay among optical excitation, temperature-dependent non-radiative relaxation, heat generation, and thermal dissipation. The model predicts the emergence of a threshold excitation power associated with intrinsic thermo-optical feedback, giving rise to pronounced slowing down of the transient dynamics, non-monotonic evolution of the characteristic transient time, population overshoot, and accelerated relaxation above threshold. These phenomena originate from the progressive establishment of a positive feedback loop linking temperature, non-radiative relaxation, quantum efficiency, and heat generation. Our results demonstrate that temperature should no longer be regarded merely as a passive external parameter, but rather as an active dynamical variable capable of continuously reshaping the relaxation pathways of the system. More broadly, this work establishes intrinsic thermo-optical feedback as a general framework for understanding nonlinear transient phenomena in optically excited RE

^{3+}

materials and provides a complementary perspective for interpreting threshold-like optical responses beyond conventional photon-avalanche mechanisms.