The Nonlinear Amplification Of The High Repetition Rate Fiber Femtosecond Laser And The Precise Control In Time And Frequency Domain

The frequency combs based on precise time and frequency control technology provide novel lasers with high resolution and stability for remote sensing in space and absolute distance measurement.The further scaling the comb spacing and the average power of the frequency comb are demanded to meet the requirements of these applications.In the recent years,the femtosecond fiber laser attracts increasing attention as the source of frequency comb for its compact and low-cost.However,there are some limitation on frequency comb applied in the distance measurement and frequency standard transfer in the framework of the existing technology.The compressed pulse duration is limited by gain narrowing in a fiber amplifier.Then,beam quality delivered from the double clad fiber is difficult to maintain in the diffraction limited at high average power.The additional phase noise becomes the significant restriction in the frequency characteristic of the frequency comb.The combination of nonlinear pulse amplification and precise control in time and frequency is an effective way to achieve high power and wide spectral fiber frequency combs power.This paper focuses on the nonlinear amplification of the high repetition rate fiber femtosecond laser and the precise control in time and frequency domain.Based on a low noise high-repetition-rate femtosecond fiber laser,a novel self-similar amplification based on pre-chirping management is demonstrated.We report on a high-power third-order dispersion managed amplification system that delivers 33-fs pulses of 93.5 W with 80-nm bandwidth.We believe that the amplifier can be used as a pump source for ultraviolet and mid-infrared frequency comb generation.Moreover,a frequency comb at high repetition rate is achieved.The details are summarized as follows:1.The mode-locked fiber laser operated at high repetition rate with low phase noise emits an evenly spaced grid of frequencies that can be used for high-repetition-rate frequency comb generation.An all-polarization-maintaining fiber laser of a nonlinear amplifying loop mirror design is developed.Then,a femtosecond pulse train is achieved with low phase noise in absence of environment noise isolation We believe that the laser design presented has a lot of potentials and can be an ideal source for improving the stability and reliability of the frequency comb.2.The chirped pulse amplifier is an ideal laser front end for the pre-chirping managed self-similar amplification.We design a space-type compressor for high-order-dispersion compensation.The Fourier transformed-limited pulses are obtained from a chirped pulse amplifier by using the grism-based compressor at the average power of 11 W.Moreover an integrated ultrashort laser system which is all-polarization-maintaining fiber designed is established.The laser system with environmental robustness is a stable and reliable laser source for absolute distance measurement.3.The ideal self-similar amplification is experimentally largely limited due to additional deleterious effects such as a limited gain bandwidth of the fiber,the higher dispersion orders,and the stimulated Raman scattering.We demonstrate an approach to suppress detrimental effects in the high-power self-similar fiber amplifier by using a grism-based pre-chirper to optimize the pulse chirp prior to the self-similar amplification.Firstly,a numerical simulation is presented to show the impact of pre-chirping GVD on pulse evolution along a gain fiber and the compressed pulse quality.We then numerically discuss the influence of the pre-chirping TOD on minimize temporal pedestals of the compressed pulses.Based on theoretical analysis,a pre-chirping managed self-similar amplifier generating 93.5 W compressed pulse with a pulse duration of 33 fs,and 51-MW peak power is demonstrated.Compared with other similar amplification systems,it has the highest peak power and the shortest pulse duration.4.The high frequency accuracy is required in space remote sensing for achieve higher resolution.The precise control in time and frequency domain is demonstrated based on the high repetition rate fiber laser and ultrashort pulse amplification.Through the feedback control of cavity length and the pump laser drive current,the repetition rate and carrier envelope phase offset frequency are phase-locked.The stabilized repetition rate had a tracking stability of 2.4×10^-11,and the residual phase noise was less than 7 mrad.Carrier-envelope offset frequency detection using a collinear self-referencing simplified the setup and enhanced the signal to noise ratio.The carrier-envelope offset frequency has been stabled by controlling the pump current with optical frequency stability of 1.1×10^-16 and residual phase noise of 16 rad.