Beschreibung:
AbstractTwo‐photon absorption of BGO is observed between 4.8 and 5.7 eV. The results confirm and extend previous investigations on two‐photon excited luminescence. In particular the two‐photon spectra do not show the first three structures observed in the reflectivity measurements. Therefore these structures should be assigned to excitonic transitions and to Bi3+ ion transitions that are parity forbidden in two‐photon spectroscopy. In the region just above the onset, the two‐photon absorption coefficient increases with the photon energy in reasonably good agreement with the theory. Above 5 eV it increases more rapidly than predicted by the present theories for direct interband two‐photon transitions.