Mechanooptical conversion

One idea would be to have a dead end of an optical fiber and pass by with an attachment chain (over some stretch) electronically excited material in such a way that the dradgging by catalyses a radiation emitting electronic de-excitation. (could probably be combined with laser like stimulated emission). At an other location along the attachment chain the material is electronically re-excited. Electronically re-excited either by mechanical means, electronic means or in any other suitable way.

Note that this approach with a chain only makes sense if in-place-re-excitation is a bottleneck.
(Kinda hope so, transporting metastable electronic excitations on an nanoscale attachment chain sounds kinda cool.)

Long enough phosphorescent decay time needed:
The phosphorescent transition will need to have a long enough decay time to be mechanically transportable from excitation-site to (catalyzed) de-excitation-site.
Maybe with advanced atomically precise manufacturing capabilities (and fine tunable unusaually large intermolecular forces) a lot bigger range of
phosphorescent systems will be acessible/developable. (TODO: Investigate design of phosphorescent centers assuming advanced gem-gum technology is available.)

No photo-bleaching:
Having the photoactive molecules in machine phase may make it possible to avoid "photobleaching" (photoactive molecules taking damage) entirely.