Research On Laser Self-injection Locking Technology Based On Optical External Cavity

With the development of resonant microoptical gyroscope,coherent optical communication and mirror array,the qualities of light source such as line width and stability are required to be higher.Although the existing commercial narrow-linewidth lasers can achieve the frequency stabilization control of the resonator cavity with the help of high precision temperature control module and frequency stabilization device,the inherent high cost and large volume of this technology greatly limit its application in micro-optical electromechanical sensing and other fields.With the development trend of high precision and miniaturization of micro-optical electromechanical system,higher requirements are put forward for narrow linewidth laser.Therefore,in view of narrow linewidth,high stability of light source of miniaturization and low cost requirements,three kinds of cavities-the optical Fiber Bragg Grating(FBG),Fiber Ring Resonator(FRR)and optical waveguide ring resonator(WRR)are been designed and prepared,respectively.Meanwhile,the ability of light source line width narrowing,the ability of noise suppression as well as the locking effect of the center frequency of light source on the resonant frequency of cavity are explored.On this basis,the center frequency locking effect of the light source is evaluated,and the line width narrowing and locking of the semiconductor laser are realized.The specific work contents and conclusions are as follows:(1)With optical fiber Bragg grating as the injection of external cavity,the light field and refractive index are simulated and analyzed,finally design parameters and complete preparation and calibration,and the line width narrowing and noise power spectral density of the output spectrum of the self-injection locking system based on fiber Bragg grating are measured and evaluated,the experimental results show that the line width after narrowing is about 52.5 k Hz.Although the line width voltage is narrowed by nearly 2 orders of magnitude,the phase noise is only at-100 d Bc /Hz,and the RIN noise is at-150 d Bc /Hz,but the noise suppression effect is unsatisfactory at high frequency.(2)In order to further narrow the line width and suppress the noise,the coupling coefficient of the fiber ring cavity is simulated,and a self-injection locking system based on the fiber ring resonator is designed.The ability of the fiber ring cavity to narrow line width,the stability of frequency and the ability to track and lock the resonant frequency are evaluated in the experiment.The experimental results show that the line width can reach 2.45 k Hz after narrowing,and the line width narrowing capacity reaches 3 orders of magnitude.The phase noise can reach-120 d Bc /Hz,relative intensity noise can reach-150 d Bc /Hz.(3)In order to suppress the phenomenon of mode hopping and spectrum drift in selfinjection locking,a self-injection locking system based on waveguide ring resonator is designed in this paper,and its different coupling spacing is simulated.The self-injection locking system based on waveguide ring resonator can suppress the phenomenon of mode hopping and spectrum drift very well.In addition,the line width narrowing capability and stability of the waveguide ring resonator as well as the tracking and locking capability of the resonant frequency of the cavity are evaluated.The experimental results show that the line width can reach 6.25 k Hz after narrowing,and the line width narrowing capacity can reach 500 times.The phase noise can reach-120 d Bc /Hz,relative intensity noise can reach-150 d Bc /Hz,which indicates that it has good stability.