Excited state absorption of pump and laser radiations in NYAB non-linear crystal operating at 1.3 μm for visible laser light generation

Excited state absorption of laser (congruent to 1.3 mu m, corresponding to the F-4(3/2) --> I-4(13/2) laser channel) and pump (790-860 nm) radiation have been investigated in Nd doped YAl3(BO3)(4) non-linear laser crystal. Laser gain slope efficiency measurements as a function of pump wavelength have been used to estimate the excited state absorption of pump radiation. On the other hand, excited state absorption cross-section in the 1300-1400 nm wavelength range has been measured by using two beam spectroscopy. We have obtained that excited state absorption cross-section for pump radiation is negligible whereas around 1.3 mu m it is comparable to the stimulated emission cross-section from F-4(3/2) state, so that the net gain cross-section becomes negative for certain wavelengths.