Study On Polarization And Phase Control Technology Of Fiber Laser In Polarization Coherent Beam Combing Synthesis System

Linearly-polarization narrow linewidth fiber lasers have a wide range of applications in industrial,medical,scientific research and other fields.However,single-channel polarization narrow-linewidth fiber laser output power is always limited due to nonlinear effects,especially stimulated Brillouin scattering(SBS).Coherent polarization beam combing(CPBC)synthesis technology is an effective technical way to break the output power limitation of single-channel linearly-polarization narrow linewidth fiber laser and obtain higher power and higher beam quality power output.In the traditional CPBC synthesis,the linearly-polarization narrow linewidth fiber laser is mainly used for CPBC synthesis.In the experimental system,only the phases of beams need to be locked.However,in practical systems,the linearly-polarized narrow-linewidth fiber is realized by a full polarization-maintaining amplifier,the system structure is complicated and expensive,and in recent years,it has been found that the mode instability threshold of the amplifier based on the full polarization-maintaining device is lower than that of the non-polarization-maintaining amplifier.In order to obtain higher power output,the researchers proposed polarization control of the non-polarization-maintaining amplifier to obtain the polarization-maintaining laser output,and then realize the CPBC synthesis through phase-locked control.However,there is currently little literature on systematic and theoretical research on the CPBC synthesis scheme for simultaneous polarization control and phase-locking control.Based on this,this paper mainly studies polarization and phase-locked control techniques in CPBC synthesis systems based on non-linearly-polarized fiber lasers.Firstly,the development status of linearly-polarization narrow linewidth fiber laser and the limiting factors of power boost are introduced.It is pointed out that beams combing synthesis is an effective technical way to furtherly improve power.The beam combing synthesis method is briefly introduced,and the phase,polarization and other control parameters are also introduced.Secondly,the theoretical model of single-channel non-polarization-maintaining fiber laser polarization control is established,and the theoretical and experimental research of the system is carried out.Based on Jones matrix and stochastic parallel gradient descent(SPGD)algorithm,a theoretical model of the relationship between the control object of polarization control and the performance evaluation function is established.Using the theoretical model,the numerical simulation of the linearly-polarized laser based on SPGD algorithm for polarization-controlled laser polarization is carried out for the first time.On the basis of theoretical simulation,the polarization control of single-channel non-polarization-maintaining laser is realized,and the linearly-polarized laser output with the polarization extinction ratio greater than 11 dB is obtained.Thirdly,a theoretical model of simultaneous polarization control and phase-locked control in a two-channel laser CPBC synthesis system is established.The numerical simulation of the system is carried out based on the theoretical model.The results of simultaneous control of phase-locking and polarization and the results of separate control are compared.An experiment of simultaneous phase-locking and polarization control of two lasers CPBC synthesis is carried out.Finally,based on the theoretical model of two laser CPBC synthesis,the theoretical model of simultaneous polarization control and phase-locking control in the CPBC synthesis system is extended to four-channel.An experiment based on simultaneous phase-locking and polarization control of four lasers CPBC synthesis is carried out.In this paper,theoretical research on simultaneous polarization control and phase-locking control in a CPBC synthesis system can provide a technical reference for high-power coherent polarization synthesis.