Investigation Of 1030nmDBR Single-frequency Fiber Laser

Single-frequency fiber lasers have attracted a great deal of attention due to their widespread applications in laser radar,interference detection,spectroscopy,laser medicine,coherent communication and so on.In recent years,with the development of design and fabrication of highly doped multi-component glass fibers,short distributed bragg reflector?DBR?linear-cavity single-frequency fiber lasers have attracted much research interest since they have advantages of narrow linewidth,compactness,low noise,mode-hop-free.In this dissertation,a short-cavity DBR fiber laser at1030 nm with commercially available highly Yb-doped silica fiber is demonstrated and investigated theoretically experimentally under the forward-pump and backward-pump conditions,respectively.In order to realize high output power of this single-frequency fiber laser,it is amplified through master oscillator power amplification.The research work in detail is shown as follows:Based on the rate equation of the Yb³⁺ levels,the output power,pump threshold and slope efficiency as a function of the length of the gain fiber in the linear cavity DBR Yb-doped fiber laser were simulated and analyzed under the forward-and backward pumping conditions,respectively.O n this basis,the amplified output power with the length of gain fiber in Yb-doped fiber amplifiers using the forward pumping configuration was also analyzed and discussed under the different pump wavelengths,signal powers,and pump powers,respectively.Under the forward-pump condition,a short-cavity DBR fiber laser operating at about 1030 nm with a 1.9 cm commercially high Yb³⁺-doped gain fiber was constructed and then experimentally investigated in detail.The effective cavity length of this fiber laser wa s 2.8 cm.A single-longitudinal mode operation was realized through narrowing the effective gain bandwidth induced by precise temperature adjustment of the PMOC-FBG and HR-FBG.The maximum output power of 134 m W in this DBR single-frequency fiber laser was obtained with the slope efficiency of 27.1% and the linewidth of 9.5 k Hz when the temperatures of the PMOC-FBG and HR-FBG were set to be 9 ? and 43.5 ?,respectively.The single-longitudinal mode operation of this DBR fiber laser was always realized when the HR-FBG temperature varied from 42.6 to 46 ? while the PMOC-FBG temperature was set to be a fixed 9 ?.In addition,the DBR single-frequency fiber laser was amplified with residual pumping amplification and the master oscillator power amplification configurations,respectively.The amplified maximum output powers under the aforementioned amplification configurations were 246 m W and 452 m W with the slope efficiency of 50.1% and 78.1% when the gain fibers were 7.5 cm and 14.5 cm,respectively.The linewidth of the amplified output was measured to be about 12.6k Hz.The performance of this short-cavity DBR single-frequency fiber laser was also studied under the backward pumping condition.When the PMOC-FBG and HR-FBG temperature were adjusted to be 9 ? and 43.4 ?,the maximum output power of this DBR single-frequency fiber laser was measured to be 126 m W with the slope efficiency of 28% relative to the pump power of 451 m W,and the linewidth was about 9.6 k Hz.The single-longitudinal mode operation of the laser was always realized under the HR-FBG temperature tuning range of 42.2 ?⁴6.3 ?.Besides,the single-frequency lasing was amplified through the master oscillator power amplification.The maximum output power of 455 m W with the slope efficiency of 75.8% was obtained with the amplified laser linewidth of 12.1 k Hz by using a 14.5 cm gain fiber.