Research On The Auxiliary Cavity Pumping Er/Yb-codoped Fiber Lasers

Er/Yb-codoped fiber laser(EYDFL)operates in the 1.5 ?m band.The laser in this band has the advantages of low transmission loss,eye safety,high fiber beam quality,and good heat dissipation performance.So,EYDFL has important application value in many areas,such as laser radar,space optical communication and non-metallic materials processing.Compared to the kilowatt output power in the 1 ?m band and 2?m band fiber lasers,the output power of EYDFL remains at hundred-watt.Studies have shown that the amplified spontaneous emission of the Yb-band(Yb-ASE),especially the backward Yb-ASE,is the main obstacle to the power scaling of EYDFL.Thermal effects in high power EYDFL also affect the increase of output power.In order to solve the Yb-ASE problem and thermal effects,the theoretical and experimental research of the auxiliary cavity pumping EYDFL is carried out,and thermal management system is optimized.The main contents of this paper are as follows:1.Theoretical study of auxiliary cavity pumping EYDFL is developed.The effects of fiber Bragg grating(FBG)reflectivity,Yb band wavelength,and pump power on laser performance are analyzed by numerical simulation.The results show that the auxiliary cavity pumping method can effectively shorten the gain fiber length,increase the output power,suppress Yb-ASE and increase OSNR.2.The thermal effect and heat dissipation system design of high power auxiliary cavity pumping EYDFL are studied.The effects of heat sink geometry,fluid inlet temperature and velocity on the output power,Yb-ASE power and temperature distribution of EYDFL are analyzed.The results show that the U-shaped groove has the best heat dissipation effect;the effective heat dissipation of the high-power EDYFL can be achieved by reasonable control of the flow rate and water temperature.3.Experimental study on the auxiliary cavity pumping EYDFL.At a maximum pump power of 18.5 W and a gain fiber length of 3.2 m,an output of 8.5 W is obtained with a slope efficiency of 48.0%.The efficiency is improved by 4.5% compared to the ordinary EYDFL.The experiment proves the effectiveness of the auxiliary cavity pumping method in suppressing Yb-ASE and improving the performance of EYDFL.