Spectral and time measurements can be performed using conventional techniques. They allow detection of effects such as SBS occurrences (time characteristics different from TMI) or SRS (spectral characteristics). Care should be taken to measure in the high dynamic range to observe early growth of parasitic spectral features, such as amplified spontaneous emission or SRS. This highly dynamic spectrum proves that SRS is undetectable.
Beam quality measurement is the most difficult part of fiber laser pointer characterization and is worth discussing separately. In short, attenuation without introducing thermal effects is the key, which can be accomplished with Fresnel reflection or low-loss transmission optical elements. In the experiment described here, a wedge-shaped plate and a pulse pump were used to decay over a time range longer than the time when TMI appeared. At an output power of 4.3 kW, the measured M2 in the x direction is 1.27 and the M2 in the y direction is 1.21.
Application of ultrafast science After the stagnation of high-power single-mode fiber laser power increase for about ten years, it now seems feasible to develop a new generation of kilowatt-class fiber lasers with excellent beam quality. The industry has demonstrated the output power of 4.3kW, and the output is only limited by the pump power. Identified the main limitations for further improvement and identified ways to overcome these limitations.
It should be noted that careful study of all known effects and subsequent optimization of the red laser pointer parameters brought about advances in fiber design and ultimately a new record of output power. It seems that further improvement and fiber adaptation to other applications are feasible, which will be the next goal.
This brings up some interesting points. On the one hand, the project partners hope to transform the results into industrial products, but further major development forces are needed. On the other hand, this technology is highly relevant to the improvement of other fiber laser systems (such as femtosecond fiber amplifiers).