2.7 μm mid-infrared Er-doped thin-film LiNbO₃-on-insulator photonic wire laser

The 2.7 μm continuous-wave laser was demonstrated theoretically on the basis of a 1480-nm-pumped Er-doped thin-film LiNbO₃-on-insulator photonic wire (Er:LNOI PW) and a three-level rate equation model of Er³⁺. Under 1480 nm pumping, the excited state absorption (⁴I_13/2 → ⁴I_9/2) and cooperative upconversion process (⁴I_13/2 → ⁴I_15/2: ⁴I_13/2 → ⁴I_9/2) populate the ⁴I_11/2 level meanwhile bypass significantly the ⁴I_13/2 level, enabling a population inversion between these two levels. The cavity length and output coupler's reflectivity at laser wavelength were optimized for maximizing laser output. Under the optimum configuration, dependences of laser power on both pump power and Er³⁺ concentration were investigated. Simulation results show that lower threshold pump power, higher laser output and slope efficiency are obtained for a higher Er³⁺ concentration. The laser output reveals a linear relationship to the Er³⁺ concentration and the relationship is strong at higher pump level. Simulation results show that the threshold pump power, laser output and slope efficiency are on orders of several tens of mW, sub-mW and 3.1%, respectively, for an Er³⁺ concentration of 1.5 mol%. In addition, there is no need to account for photorefractive effect on the laser performance as it is far smaller than the refractive index contrast of the LNOI PW, ∼0.7. Present work opens up the possibility of implementing an on-chip 2.7 μm mid-infrared laser based on an Er:LNOI. © 2023 Elsevier B.V.