Numerical Investigation of 1662 nm Holmium-Doped Fiber Lasers Enabled by a 751 nm Fiber Laser Pump

In this study, we present a novel fiber laser that employs self-pumping from internal laser transitions to induce inversion in other transitions. Using the ${}^{5}\mathrm{F}_{4} + ^{5}$ S $_{2}\to ^{5}$ I5 laser transition at 1354 nm to populate the 5I5 level, the cascade laser oscillation at 1662 nm ( ${}^{5}\mathrm{I}_{5}\to ^{5}$ I7) in Ho3+-doped ZrF4 (Ho3+: ZrF4) fiber was investigated. A practical design of the cascade laser, which is pumped by a 751 nm fiber laser, is determined by modeling it using an eight-level rate equation system that involves experimental spectroscopic parameters. By utilizing a 1.3-m-long Ho3+: ZrF4 fiber with a dopant concentration of 0.1 mol.% and assuming a pump power of 10 W launched into the fiber’s core, the simulation results show that this cascade system can achieve a slope efficiency of 38.9% and a maximum output power of 2.94 W. The result obtained prompts the development of a 1662 nm fiber laser that is based on a commercially available ZrF4 fiber. This laser has potential for a variety of applications, including telecommunications, gas sensing, multiphoton fluorescence microscopy, and pump sources.