Spectroscopic analysis and laser simulations of Yb<sup>3+</sup>/Ho<sup>3+</sup> co-doped lead-germanate glass
Mamoona Khalid, David G. Lancaster, Heike Ebendorff‐Heidepriem
Abstract
The potential of a Yb 3+ /Ho 3+ co-doped lead-germanate glass as a laser gain medium around 2 µm is investigated by spectroscopic measurements and rate equation modelling. The glass, based on the molar composition of 56GeO 2 -31PbO-4Ga 2 O 3 -9Na 2 O and co-doped with 1.5 mol% Yb 2 O 3 and 0.4 mol% Ho 2 O 3 , possesses a broad Ho 3+ emission spectrum covering ∼1.8 µm to 2.2 µm for the Ho 3+ : 5 I 7 → 5 I 8 transition, and a long 5 I 7 fluorescence lifetime of (7.74 ± 0.03) ms. We estimate a competitive 2 µm quantum efficiency (76%) compared to other germanate glasses. The intensity parameters are calculated to be Ω 2 = 3.0×10 −20 cm 2 , Ω 4 = 1.2×10 −20 cm 2 and Ω 6 = 2.0×10 −20 cm 2 . The energy transfer analysis from Ho 3+ to OH group represents a low Ho 3+ -OH clustering factor ( γ = 0.15) compared to phosphate and other germanate glasses. Applying these parameters to the laser model predicts > 15% laser slope efficiency for cavity losses ≤ 0.5 dB using 976 nm pumping. The results show that this Yb 3+ /Ho 3+ co-doped lead-germanate glass is a promising candidate for efficient lasing around 2 µm.