Functionalized Mode-Locked Fiber Laser Frequency Comb And Timing Technology Research

Optical frequency comb(OFC)is undoubtedly one of the discoveries that has attracted the most attention from researchers in recent years.It is an equal interval ultrashort pulse sequence in the time domain,and consists of a series of frequencies with equal frequency intervals in the frequency domain.OFCs have also been applied in the fields of precision spectroscopy,precision time-frequency standards,synchronization of precision clock signals,spatial positioning,medical imaging,etc.As a producing method of stable OFC,the mode-locked fiber laser frequency comb also has great research value and application potential because of its peak power,narrow pulse width,and low noise easy frequency adjustment and good robustness.In the above background,many methods of mode-locked fiber laser frequency combs capable of generating stable,high pulse energy and repetition frequency variation are discovered.Passive mode-locking method has become the main realization method of mode-locked fiber laser frequency comb source,due to its advantages of simple structure,small equipment,easy packaging,low cost,stability and long service life.With the expansion of application scope and the improvement of demand,the mode-locked fiber laser frequency comb requires the light source to have the characteristics of good robustness,high pulse energy,long service life and wide spectrum etc.However,the stability of existing combs is affected by polarization,the pulse energy is limited,the lifetime of saturable absorbers is also limited by high peak power damage,and the spectral width is affected by net dispersion.Therefore,this thesis is based on the cavity structure design and implementation of the functionalized mode-locked fiber frequency comb to improve the single pulse energy and stability of the output pulse,achieve innovation and breakthrough in terms of physical mechanism,structure and the output performance indicators.The comb excited by different physical mechanisms has realized.At the same time,combined with timing technology,the output regulation and timing technology application can be realized based on the mode-locked laser frequency comb.The main research contents are briefly introduced as follows:(1)First of all,the thesis investigating the current research status of the development of OFC,focusing on the detailed research status and timing technology based on modelocked fiber laser frequency combs,discussing the current research status and scientific problems encountered.The research significance of this topic is proposed.(2)Further,the physical generation mechanism of the mode-locked fiber laser frequency comb is described,the dispersion effect,various nonlinear effects of the optical pulse in the fiber and the generation principle of the Kelly sideband are analyzed.And the asymmetry of its Kelly sideband is analyzed in combination with the nonlinear effect.Finally,based on the performance improvement of the functionalized mode-locked fiber laser frequency comb,a highly nonlinear fiber(HNL)is added to the design of the experimental structure.The consumption of the soliton energy by the dispersion wave is greatly compensated for the interaction between the high nonlinearity and the Kelly sideband under high pump power,improving the soliton energy from 0.1n J to 3.2n J,while the peak power is as high as 47 k W,with the pulse width and phase noise as low as 77 fs and-160.1 d Bc/Hz @ 7k Hz,respectively.(3)Thirdly,a corresponding pulse source structure is proposed for the mode-locked laser frequency comb source with repetition frequency variation,polarization insensitivity and wide spectrum requirements.Introducing the repetition frequency 1MHz and 100 MHz fiber laser frequency comb source to solve the requirement of repetition frequency change;introducing the all polarization-maintaining figure-9 fiber laser frequency comb source to solve the high stability and polarization insensitivity;introducing further optimization of the debugging process required by the wide spectrum,the output spectral width is increased from 15 nm to 25 nm.(4)Finally,according to the application requirements of timing technology,the origin of dispersive Fourier transform technology and the performance improvement of time-stretched dispersive Fourier transform(TS-DFT)are introduced.Proposes and realizes the timing technology of spectral interferometry based on TS-DFT,and completes the analysis of measured and theoretical values with a time delay of 2-20 ps,with an average error of 2.2%,which can achieve ps level time delay accuracy.