Research On Pulsed Fiber Lasers And Ultra-stable Fiber Optical Frequency Comb

The development of modern science and technology depends on precision optical interferometers.The emergence of optical frequency comb(OFC),has built a precision and coherent link between optical and microwave frequencies.At the same time,optical frequency comb,acting as a major breakthrough in the field of optical precision measurement,pushed precision measurement science to the extremep.The wide spectral range,high stability of OFC have turned it into a powerful tool for precision spectroscopy research,and opens new frontiers in such fields as terahertz technology,astro-comb,distance measurement,molecule spectroscopy,optical clocks,time and frequency transfer,attosecond pulse generation,exoplanet exploration and so on.Because of its compact size,robustness and simple operation,fiber OFC has become one of the mainstream technologies in the development of OFC.In addition,the fiber OFC with low phase noise will further innovate precision measurement technology with finer line width and frequency stability.In view of the important application prospect of fiber OFC,the experimental study on the seed source and stability of fiber OFC is carried out in this paper,and the main research contents and innovative achievements in this thesis are summarized as follows:1.The ultra-short pulse width and ultra-low phase noise fiber laser for OFC seed source is developed.Aiming at the core source of fiber OFC,the characteristics of Erdoped fiber laser(EDFL)based on several different mechanisms are studied,and the ultra-short pulse laser output are realized.Firstly,an EDFL is built based on nonlinear polarization rotation(NPR)mode-locked technique.The resonant cavity is equipped with electro-optical modulator for the realization of repetition rate control;the fiber output is used to improve the power stability during subsequent amplification.Secondly,a new type of saturable absorber(SA)was prepared by using two dimensional nanomaterials.Based on hybrid modulation technology,the nanosecond level Qswitched EDFL and mode-locked EDFL are realized.Compared with other fiber lasers with the same type,the fiber lasers developed in this paper have the narrowest pulse width,the widest spectral spectrum and the lowsest time jitter.2.The full controlled Yb-doped fiber OFC has been realized with the frequency synthesizer as the reference source.A ?-2? system was built to detect the carrier envelope phase signal(ceof)and the signal to noise ratio is 40 dB under 100 kHz resolution.By regulating the pump current and the insertion of intra-cavity wedge,carrier envelope phase shift signal was precision locked precisely with 1.2×10-17/s frequency stability.For the repetition rate(repf)locking,we extracted the fourth harmonic that is 1GHz microwave signal,and adjusted the cavity piezoelectric ceramic drive voltage to control the repetition rate,and we got 2×10-12/s frequency stability,which is limited by the stability of the reference source on the order of 10-12/s.Once locked,the time jitter ofrepf is reduced from 52 ps to 8.2ps(integred from 1Hz to 1MHz),it is proved that the PLL circuit has a certain suppression effect on the phase noise.To further improve the frequency stability of therepf,only the reference source is promoted to the optical reference source.3.The spectral broadening of Yb-doped fiber OFC is realized,which is proposed to stabilize the Yb-doped fiber OFC to the 972 nm Continous Wave(CW)optical signal in our lab.Due to the 972 nm component directly from the Yb-doped fiber OFC is too weak to generate beat signal,the seed light from Yb-fiber oscillator with 6.7ps pulse width and about 30 mW average power was delivered to two stage Yb-doped fiber amplification system and then compressed with a pair of grating.The output spatial light with 2W average power and 110 fs pulse width is coupled into the photonic crystal fiber(PCF)to generate supercontinuum(SC)spectrum covering from 350nm-1650 nm,and 972 nm component is amplified and enhanced.4 The ultra-stability Yb-doped fiber OFC with 10-18 level stablity in loop is realized.Firstly,we obtained the ultra-stable narrow linewidth laser by locking the 972 nm CW laser to the ultra-high fineness and stability Fabry-Perot(F-P)cavity with Pound-drever-hall(PDH)technology.Secondly,the Yb-doped fiber OFC is loced to the ultra-stable narrow linewidth 972 nm laser.The line width of the comb mode is about 200 kHz in free running.After locking,the line width is suppressed to megahertz order and the frequency stability reaches 2×10-18/s.The time jitter is 278as(integred from 1Hz to 10MHz).As far as we know,the result is the highest frequency stability of the Yb doped fiber OFC so far.