Research On A New Type Of Ytterbium-doped Mode-locked Optical Fiber Laser Based On 915nm Dual Pump

Laser of 980nm band has various applications.It can be used as seed light for all kinds of solid-state laser and amplifier.It can also be converted into near 480nm blue green light through frequency multiplication technology,replacing the traditional inefficient argon ion lasers and semiconductor blue lasers as the source of the underwater correspondence.Since 980nm is also used as the launching peak and absorption peak of ytterbium,one of the key technologies in this band is to avoid or inhibit the reabsorption effect of 980nm laser.Through theoretical analysis and numerical simulation,the feasibility and key techniques of the locking module in 980nm are analyzed,and the importance of the filter structure is verified in the all-normal dispersion condition.In the experiment,we use 915nm laser as pump source,ytterbium-doped fiber laser as gain medium and reflective diffraction grating as the filter structure.Finally,we successfully built a fiber laser that operates stably in all-normal dispersion conditions.The pulse spectrum width of the stabilized laser output has reached 11.4 nm,which is very close to the gain bandwidth of ytterbium ions in this band.Due to the large chirp accumulated in all-normal dispersion cavity environment,the direct output pulse width is 1.6 ps,and the pulse width is reduced to 180fs by means of external compression.We also confirmed that the increment of pump power within a certain range could lead to increment of mode-locked pulse spectrum width,and found a surprising resonance phenomenon between the light of 980nm band and that of 1030 nm at the same time,the spectrum bandwidth appears larger as a result.By introducing grating pair in the cavity to adjust the dispersion,we got disparate mode-locked pulses at 980nm,which proved the effect of intracavity net dispersion on mode-locked pulse characteristics.