Research Of Low-Threshold Mid-Infrared Optical Frequency Comb Generation Based On Ⅲ-Ⅴ Microcavities

Optical frequency combs based on microring resonators(microcavity optical frequency combs)have the unique advantages of high repetition frequency,wide spectral range,and small system volume,and have broad application prospects in the fields of precision measurement and optical atomic clocks.The mid-infrared band covers two atmospheric windows and the characteristic absorption peaks of various molecules,which is of great significance for space optical communication,molecular spectroscopy detection,etc.However,compared with other bands,it usually faces serious challenges such as pump sources and coupling devices.Therefore,how to realize low-threshold mid-infrared microcavity optical frequency comb generation has important research significance.This paper is mainly based on the Ⅲ-Ⅴ material microcavity.By taking advantage of its high nonlinearity of the second and third order,combined with the optimized design of the microcavity structure,generating the lowthreshold mid-infrared microcavity optical frequency comb.Furthermore,we investigate the influence of various nonlinear effects on the physical properties of optical frequency combs,and a feasible scheme for the simultaneous generation of midinfrared and near-infrared optical frequency combs in microcavities is explored.The main research contents and innovations are as follows:1.Based on the nonlinear Schrodinger equation(NLSE)in the optical fiber and the periodic boundary conditions of the microcavity,the Lugiato-Lefever equation(LLE)obeyed by the light field transmission in the microcavity is derived,and the fractional-step Fourier algorithm is used to calculate it.The numerical solution is carried out,and the dynamics of the generation of the optical frequency comb based on the four-wave mixing effect in the microcavity under continuous optical pumping is expounded.The results show that the flat near-zero negative dispersion is beneficial for the excitation of broadband mid-infrared microcavity soliton optical frequency combs,and the higher-order dispersion contributes to the further expansion of the bandwidth of the optical frequency comb.2.Through the optimized design of the structure and dispersion parameters of the Ⅲ-Ⅴ material microcavity,the generation process of the low threshold broadband midinfrared microcavity optical frequency comb is theoretically studied by using the characteristics of its high third-order nonlinear coefficient.The results show that when the pump power is 34 m W,a broadband mid-infrared optical frequency comb with a repetition frequency of 467 GHz and a spectral width of over one octave can be generated in the gallium phosphide microcavity,and its parametric oscillation threshold is only 4 m W;the pump power at 15 m W,an octave-band mid-infrared optical frequency comb with a repetition rate of 100 GHz can be generated in an Al Ga As microcavity with a threshold of only 0.5 m W.3.Based on the strong second-order nonlinearity of Ⅲ-Ⅴ material microcavity,the possible way of simultaneous generation of near-infrared and mid-infrared optical frequency combs in integrated waveguides and microresonators is theoretically studied.The results show that by using the mid-infrared optical frequency comb as the pump light field,the conversion of the near-infrared optical comb can be achieved in a short gallium phosphide waveguide through the sum-frequency and frequency doubling effects;while using the near-infrared optical frequency comb as the pumping field The optical field,under the condition of satisfying specific phase matching conditions,can realize the efficient generation of mid-infrared optical frequency comb in the Al Ga As arsenic microcavity.