Challenges faced by high-power continuous thulium-doped fiber lasers, Over the past two decades, the output power of continuous thulium-doped fiber lasers has increased dramatically. The output power of a single all-fiber oscillator has exceeded 500 W; the all-fiber MOPA structure has achieved an output power of kilowatts. However, there are still many problems restricting further improvements in power.
First of all, when the power increases, the system will generate a large amount of heat, which will seriously affect the increase in output power and the stability of the laser, and may even cause damage to the laser. Therefore, effective heat dissipation is crucial. By using a multi-stage amplification structure, the heat distribution of the system can be effectively dispersed and the pressure on thermal management is reduced. Using a pump source with a wavelength close to that of the laser can reduce quantum losses and reduce heat production. In addition, some new optical fibers with good heat dissipation properties, such as metal-clad optical fibers, also provide new ideas for thermal management.
Secondly, the higher the laser output power, the more obvious the nonlinear effect in the optical fiber will have on the power increase. Some new large-mode field photonic crystal fibers have higher nonlinear thresholds, which can effectively reduce the impact of nonlinear effects.
In addition to the influence of temperature and nonlinear effects, the performance of 2 μm optical fiber devices also restricts the improvement of output power to a certain extent. When the power exceeds the maximum power of the optical fiber device, the device will be damaged, and high power causes Increased temperature affects the performance of fiber optic devices.
Therefore, developing high-stability, high-power-withstanding optical fiber devices is an important way to further increase the output power of thulium-doped fiber lasers. In addition, the absorption efficiency of the pump light by the gain fiber and the brightness of the pump source are also important factors affecting the power increase.
Generally speaking, improving the output power of thulium-doped fiber lasers can start from the aspects of achieving effective temperature control, developing high-efficiency thulium-doped fibers, overcoming nonlinear effects, improving fiber device performance, optimizing system structure, and improving pump source brightness.