Research On Control Of Optical Pulse’s Repetition Rate And Optical Frequency Comb’s Line Spacing Based On Talbot Effect

Talbot effect was first discovered by the scientist H.F.Talbot when he studied spatial diffraction.Then,based on the duality between spatial diffraction effect and temporal dispersion effect,the Talbot effect is extended from space domain to time domain.Similarly,based on the duality between time domain and frequency domain,the Talbot effect is further extended to the frequency domain.After years of exploration and summary,the Talbot effect has been widely used in spectral analysis,repetition-rate control of optical pulse,noiseless amplification of optical frequency comb lines and other fields due to its simple implementation and high energy efficiency.In this paper,the spatial Talbot effect is firstly introduced,and then the research status and operation principles of the temporal Talbot effect and the spectral Talbot effect are deeply analyzed.Based on the spectral Talbot effect,an optical frequency comb line spacing control system is proposed.In addition,an optical pulse repetition rate control system based on the generalized temporal Talbot effect is designed.The operation principles of the two systems are analyzed in detail theoretically,and the important formulas are derived.The feasibility of the proposed systems is verified by numerical simulations.The influence of system error is analyzed and the potential applications of the designed systems are discussed.The main content and research results of this paper are as follows:1.The spectral amplitude filtering function of optical tapped delay line(OTDL)structure is studied and the spectral response function of the OTDL is analyzed in detail.By cascading an OTDL with a phase modulator,an optical frequency comb line spacing control system is designed,which can achieve the arbitrary line-spacing control of the input optical frequency comb.Simulation experiments are performed to change the line spacing of the input optical frequency comb from 10 GHz to 30 GHz,40 GHz,40/3GHz,25 GHz,5 GHz,10/3 GHz,7.5 GHz and 8 GHz,respectively,to verify the functions of the proposed system.In addition,the influence of OTDL delay error and phase noise on the output optical frequency comb is analyzed.Compared with the existing scheme,the designed system avoids the problem of using dispersive medium with large dispersion amount,and the simulation results show that the system has certain anti-interference ability,so as to ensure its stability.This scheme has potential applications in high-resolution spectroscopy,frequency measurement and other fields.2.The concept of generalized temporal Talbot effect is studied and the corresponding relation between the dispersion amount and the specific OTDL structure in performing temporal Talbot effect is derived.By combining a phase modulator with a specially designed OTDL,an optical pulse repetition rate control system is proposed,which can achieve the arbitrary repetition-rate control of the input optical pulse signal,including integer repetition-rate multiplication,fractional repetition-rate multiplication,integer repetition-rate division and fractional repetition-rate division.Through numerical simulations,the repetition rate of the input optical pulse train is changed from10 GHz to 30 GHz,60 GHz,15 GHz,40/3 GHz,10/3 GHz,2.5 GHz,20/3 GHz and 4GHz,respectively,to verify the feasibility of the designed system.The influence of OTDL delay error and phase error on the output optical pulse signal is studied and analyzed respectively.Compared with the traditional scheme,the designed system uses OTDL instead of dispersive medium to realize the temporal Talbot effect,thus avoiding the influence of high-order dispersion and nonlinear effect.This scheme expands the repetition-rate adjustment range of optical pulse train and provides a potential solution for generating optical pulse train flexibly.