Figure 2

(a) Schematic diagram of Nd³⁺ energy levels under excitation at 808 nm. (b) 2D color-map of the PL intensity (in color) as a function of the wavelength (y-axis) and the pump photon flux (x-axis). (c) Intensity of a lasing resonance (left y-axis scale) and wavelength shift relative to the value of the cold-cavity resonance wavelength (right y-axis scale) as a function of the incident photon flux. Dashed lines mark the values of the incident photon flux at which time-resolved measurements were performed (see Fig. 4).