Figure 2
APS/Alan Stonebraker; Adapted from Ref. [4]

Figure 2: Three molecule lasing system including a “triplet manager.” Pump photons excite the singlet states of the triplet manager and host molecules (lower energy states are omitted for clarity), which populate the guest singlet state that produces the laser photon. Although the guest triplet state can be populated by the host triplet, both transfer energy to the lower-lying triplet state of the triplet manager. The depopulated guest triplet can then no longer absorb laser photons.