Generation of multi-wavelength visible light in Er³⁺-doped and Er³⁺/Yb³⁺-doped single-mode optical fiber pumped at 1313 NM

We report the generation of multi-wavelength visible light through'amplified spontaneous emission (ASE) in Er³⁺-doped and Er³⁺/Yb³⁺-doped germanosilicate single-mode optical fiber pumped by a Nd:YLF laser at 1313 nm. In the Er³⁺-doped fiber, the intense multi-wavelength blue emission lines around 463-510 nm correspond to transitions from 2G_7/2 etc. excited states to the metastable 4I_13/2 state, and their pumping mechanism is accomplished by a stepwise four-photon absorption. Some emission lines in this wavelength region are attributed to the three-wave sumfrequency process of 1313 and 1530nm (corresponds to ⁴I_13/2-⁴I_15/2)- The intense green emission lines at 525 and 540 nm are also observed in the Er3+-doped fiber. In the Er³⁺/Yb³⁺-doped fiber the blue and green lines are very weak compared with those in the Er³⁺-doped fiber.