| Green laser plays a substantial role in storage,display,and especially in underwater communication as well as detection.Seeking for new-style,stable and efficient green light source has become a hot topic.Upconversion technology is a common and mature method to generate green laser.The laser made by upconversion technology has the advantages of simple structure,high performance and so on.Internationally,in the investigations of red pumped Ho:ZBLAN upconversion fiber laser,the output power was difficult to be improved.The reason can be largely attributed to the red-light pump source(low power,poor beam quality).Therefore,we have explored how to generate red laser with high power and good beam quality,and we focused on the LD-pumped solid-laser.In the experiment,three resonant cavities with different lengths of 500mm,75mm and 95mm were used for comparison.Although the outtput power obtained by the three cavities is similar,but the M2 of the output from the cavity length of 50mm in the x direction and y direction is 1.33 and 1.15 respectively,which is the best among the three.Therefore,the 50mm long resonator was selected as the final choice for the experiment.The final red-light output power is 2.128 W,and the red-light power of coupling into the fiber is 1.045W.The next step is to achieve green output from Ho:ZBLAN upconversion fiber laser after we obtaining considerable red pump source.The substantial theory of this experiment is upconversion technology.We used Ho3+-doped fluoride fiber with a length of 15cm and doping concentration of 5000ppm as gain medium.The Ho3+ ion has a strong absorption in the band of 639nm and a strong fluorescence emission in the range of 540-550nm.Finally,a maximum output power of 72mW of green laser had been obtained,which is the highest as we know.By calculation,the slope efficiency is 9.2%and the pump threshold power is 139mW.The central wavelength of the output is tunable in the range of 546-549.9nm,spectral half-width is 1.4nm. |
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