Study On Optical Frequency Combs Based On Pulsed Synchronous Pumping Of Normal Dispersion Microring Resonators

Optical frequency combs are composed of a series of discrete and equally spaced periodic pulse sequences.Due to the large number of spectral lines and the same spectral line spacing,they can accurately measure the unknown frequency and have a large number of applications in lidar,optical communication,and astronomy.The optical frequency comb based on nonlinear Kerr effect in the normal dispersion region has the characteristics of good flatness,high pumping efficiency and good coherence.There are two main ways to generate optical frequency combs based on nonlinear Kerr effects: cavityless fibers/optical waveguides and microring resonators.In this paper,dual-frequency laser pumping cavityless nonlinear optical waveguides based on supercontinuum broadening and pulse/dual-frequency laser pumping micro-ring resonator two schemes are studied to generate optical frequency combs.The main research results are as follows:(1)Dispersion control of the TE0 fundamental mode in the multimode Al Ga As optical waveguide is performed to achieve normal dispersion.The dual-frequency laser is injected into the nonlinear normal dispersion Al Ga As optical waveguide after pulse compression,using normal dispersion,self phase modulation and optical wave breaking effect to generate flat optical frequency combs.The time-frequency evolution process of the dual-frequency laser after pulse compression and transmission in the nonlinear normal dispersion Al Ga As optical waveguide is simulated and studied,and an optical frequency comb with a flatness of 5d B and a bandwidth of 125 nm is realized.The effects of changing different parameters on the resulting optical frequency combs,such as changing the frequency interval of the dual-frequency laser,changing the power ratio of the dual-frequency laser and changing the pulse shape after pulse compression and shaping are studied.(2)Dispersion control of the TE0 fundamental mode in the multimode silicon nitride microring resonator is performed to achieve normal dispersion.Using dualfrequency laser/electro-optical modulated pulsed laser as pump source injected into a normal dispersion Kerr silicon nitride microring resonator to generate optical frequency combs.The time-frequency evolution process of the optical frequency combs generated by changing the detuning of the pump when the dual-frequency laser/electro-optically modulated pulsed laser is injected into a normal dispersion Kerr silicon nitride microcavity as a pump source is simulated and studied,and an optical frequency comb with a bandwidth of 100 nm is realized.The influence of varing different parameters,such as changing the total input power,intra-cavity loss,intra-cavity dispersion and other conditions on the resulting optical frequency combs are investigated.(3)The 90-degree Euler bend and the 180-degree Euler bend are optimized to realize the connection between the curved optical waveguide and the straight optical waveguide and effectively suppresses the excitation of higher-order modes in the multimode optical waveguide.The Spiral multi-mode Al Ga As optical waveguide was designed by using 90-degree Euler bending,and the racetrack-type microcavity with FSR of 100 GHz was designed by using 180-degree Euler bending.The corresponding array layout was drawn.Secondly,in order to improve the coupling efficiency between the high numerical aperture fiber and the Al Ga As optical waveguide and improve the power bearing capability of the Al Ga As optical waveguide,a double-layer inverted taper coupling structure based on silicon nitride is designed,which is constructed by 3D FDTD.The simulation achieved the coupling efficiency of 85%.