Research On Obtaining Microwaves And Microwave Frequency Combs Based On The Nonlinear Dynamics Of Semiconductor Lasers Under External Disturbances

Microwave signals and microwave frequency comb（MFC）signals play an important role in the fields of communication,military,medical,information,and so on.The traditional electrical methods mainly utilize the nonlinear effect of electronic devices such as diodes and transistors to generate microwave signals and MFC signals,but due to the bandwidth limitation of the electronic devices used,it is difficult to obtain high frequency millimeter wave and broadband MFC based on the electrical methods.Also,the millimeter wave signals and MFC signals generated by electrical methods also face the problems of frequency instability,poor amplitude-frequency characteristic and large phase noise.In contrast,the photonics methods show the superior performance with high speed,large bandwidth,low loss,anti-electromagnetic interference,and it is of great significance to explore optical generation technologies of high quality millimeter wave and MFC from both the academic and application aspects.Semiconductor laser（SL）possesses some unique advantages of small size,light weight,low cost,easy integration,easy to be directly high-speed modulated,etc.Under external disturbances such as optical injection,optical feedback,and optoelectronic feedback,SL can exhibit different dynamical states including periodic oscillation,multi-periodic oscillation,chaos,harmonic frequency locking,regular pulsing state,and chaotic pulsing state.These nonlinear dynamical states can be extensively applied in photonics microwave,optical chaotic communications,satellite communications,radar system,the generations of random number and MFC.Therefore,the thesis focuses on the nonlinear dynamics of SL and the applications of SL in high frequency millimeter wave and broadband MFC,and explores the novel generation methods of high frequency low noise microwave signals and broadband MFC signals.The main work and results are summarized as follows:1.The nonlinear states and dynamic evolution of the dual-beam optical injection SL are experimentally investigated.Based on the experimental system of dual-beam optical injection SL,the influences of injection strengths and detuning frequencies of two injection beams on the nonlinear dynamics of SL are analyzed,and three dynamics scenarios of dual-beam optical injection SL under different detuning frequency cases are discussed.The results show that three dynamics scenarios,which are categorized as scenarios A,B,and C,have been observed for three cases of dual-beam detuning frequency,and each scenarios includes some typical dynamical states.Furthermore,the appearances of three dynamics scenarios are closely related to injection strengthsξ₁ andξ₂ of two beams.The dual-beam injection SL displays C scenario with very weak injection strengthsξ₁ andξ₂.The dual-beam injection SL displays B scenario with a weak injection strength and a strong injection strength.The dual-beam injection SL displays A scenario with both strong injection strengthsξ₁ andξ₂.In addition,by analyzing the mappings of dynamics scenarios and states as a function of two injection strengthsξ₁ andξ₂ under three cases of detuning frequency,we find that the competition and balance between two injection beams determines the dynamical behavior and dynamical scenarios of the dual-beam optically injected SL,and the SL generally undergoes the evolution trend of scenario B to scenario A and finally to scenario AB.2.A scheme for generating high frequency pure 60 GHz band millimeter wave based on SL is proposed and verified experimentally.First,based on a SL subjected to optical injection and current modulation,the 1/3 and 1/4 subharmonic microwave modulation technique is explored.The experimental results show that after adopting 1/3and 1/4 subharmonic microwave modulation,significant reduction in linewidth and phase noise of the photonic microwave originated from the P1 oscillation in an optically injected SL can be achieved.Also,for varying modulation power P_m or modulation frequency f_m,microwave signal will undergo the process of out of locking to locking and finally to out of locking.Based on the low order subharmonic microwave modulation,a high order subharmonic microwave modulation is further investigated,and high purity millimeter wave generation at 60 GHz band is experimentally demonstrated via 1/4 and 1/9subharmonic microwave modulation.The experimental results show that for the optically injected SL operates at a P1 state with a fundamental frequency f₀=49.43GHz（45.02 GHz）,by introducing 1/4（1/9）subharmonic modulation,a high purity61.28 GHz（65.07 GHz）millimeter wave with single sideband phase noise below-96dBc/Hz@10 kHz（-98 dBc/Hz@10 kHz）is experimentally obtained.Also,for 1/4and 1/9 subharmonic modulation,the obtained 60 GHz band microwave frequency can be tuned in a certain range through adjusting f_m and selecting matched P_m.3.A scheme for generating tunable and ultra-broadband MFC based on SL is proposed and verified experimentally.The performances of a seed MFC generated by a current modulated SL and a final MFC output from a current modulated SL under optical injection are compared,and the influences of injection power P_i,modulation frequency f_m,and modulation power P_m on the characteristics of MFC are analyzed.The experimental results show that for a seed MFC generated by a current modulated SL,via further introducing continuous wave optical injection,the performance of MFC can be dramatically improved,the bandwidth of MFC is increased and the phase noise of MFC is reduced.Furthermore,the dependence of MFC bandwidth on the operation parameters is also investigated.The results indicate that MFC bandwidth varies with P_i,f_m,P_m,and tunable ultra-broadband MFC can be obtained under suitable and matched operation parameters.4.A scheme for generating broadband and flat MFC based on SL is proposed and verified experimentally.Based on a SL2 subjected to regular pulse injection from a current modulated SL1,the characteristics of a seed MFC output from the current modulated SL1 and a final MFC output from the pulse injected SL2 are analyzed,and the dependences of final MFC bandwidth on injection power P_i and modulation frequency f_m are also investigated.The experimental results show that a seed MFC with bad amplitude flatness and only 14.4 GHz bandwidth can be generated based on a current modulated SL1,via further injecting the seed MFC into the SL2,the final MFC output from the pulse injected SL2 has better amplitude flatness and greater 33.6 GHz bandwidth.Also,the final MFC owns purity spectral characteristic and low phase noise.Furthermore,the variation trends of final MFC bandwidth with P_i and f_m are also analyzed.The experimental results indicate that with the increase of P_i,the bandwidth of final MFC increases first and then decreases.Through selecting suitable P_i,the final MFC with bandwidth greater than 30.0 GHz can be obtained.In addition,the comb spacing of final MFC can be tuned easily by adjusting the modulation frequency f_m.