Non-Lorentzian line shape of a forced two-level system described by a nonlinear Schrödinger equation

We calculate the response of a two-level system to a monochromatic excitation in the framework of a nonlinear homogeneous dissipative generalization of the Schrödinger equation. Non-Lorentzian dependences of the real and imaginary parts of the dynamical response function on the frequency are predicted.