Ytterbium Fiber Optical Frequency Comb And Femtosecond Amplifier

With excellent frequency stability,femtosecond optical frequency comb has been widely applied in many research fields,such as high-resolution spectroscopy,metrology,absolute distance measurement,fundamental physical constant measurement,optical frequency standard,and so on.For such an important research tool,this dissertation presents the research on Yb-doped fiber optical frequency comb.And for the purpose of improving the average power of fiber optical frequency comb,the femtosecond fiber amplifier with high repetition rate is studied.The main innovative achievements are summarized as follows:1.Based on the technique of nonlinear polarization rotation mode-locked,the Yb-doped fiber oscillator operating in dispersion-managed regime is realized.Firstly by adjusting the distance between the transmission gratings,the net cavity GDD is set in the range of near-zero,stable mode-locked pulses are produced.The broadest spectrum of the mode-locked pulses spanned from 950 to 1150 nm with a repetition rate of 124 MHz.The shortest duration of the de-chirped pulses is 32 fs after extra-cavity compression.Secondly in view of the complexity of the nonlinear polarization rotation mode-locked fiber oscillator for operation and maintenance,a set of automatic mode-locked controller is developed.The electronic signal detected by a photoelectric detector is sent into the controller for signal processing and logic judgment to produce a feedback control signal.The feedback control signal controls three wave-plates intra-cavity to rotate at different speeds,stable mode-locked pulses are obtained while count criterion and harmonic criterion are both logically true at the same time.The search process of the mode-locked state takes less than 90 seconds with a success rate close to 100%.2.The all polarization-maintaining Yb-doped fiber oscillator based on the principle of SESAM mode-locked is studied.Using a chirped fiber Bragg grating to compensate the positive dispersion introduced by the fibers and other optical components intra-cavity,the net dispersion is set to about +6000 fs2.When the pump power is 310 m W,stable mode-locked pulses operating in self-similar regime with a repetition rate of 67.8 MHz are obtained.3.Based on the self-built Yb-doped femtosecond fiber laser,we carry out the experiment research of optical frequency comb.Firstly,an octave-spanning super-continuum spectrum from 500 to 1500 nm is generated by injecting the de-chirped pulses into a section of tapered single mode fiber.The diameter and length of the tapered region are about 3 ?m and 9 cm,respectively.Then based on f-2f self-reference technique,a CEO signal with a high SNR of up to 44 d B and a line-width of 110 k Hz have been obtained.Eventually,the 1)0) and 1) signals are phase-locked simultaneously to microwave reference sources by the phase-locked loop circuits.After phase-locking,the standard deviation of the 1)0) is 0.7 m Hz,and the Allan deviation is 2.26×10-13 in a gate time of 100 s.The standard deviation of the 1) is 3.9 m Hz,and the Allan deviation is 1.97×10-13 in a gate time of 100 s.4.In order to meet the requirements of dual-comb absolute distance measurement,we build a set of Yb-doped fiber optical frequency comb with a high repetition rate of about 250 MHz.Firstly,we construct an Yb-doped fiber oscillator mode-locked based on NPR technique with a repetition rate of more than 300 MHz.Meanwhile,a EOM crystal and a pair of optical wedges have been successfully inserted into the cavity.Then,also using the tapered single mode fiber to extend the spectrum of de-chirped pulses to an octave bandwidth.The long stability of optical frequency comb system has been greatly improved by optimizing the structure design of coupling optical path.Finally,using f-2f self-reference technique,a CEO signal with a SNR of more than 30 d B has been detected.5.Using the self-built 250 MHz Yb-doped fiber optical frequency comb,we measure the absolute frequency of the 32D5/2-42S1/2 clock transition of the 40Ca+ ion.Firstly,we build a set of non-PM fiber amplifier to amplify the laser pulses in the 45% route of oscillator.The average power of the compressed pulses is 4.4 W with the shortest duration of 174 fs.Secondly,the super-continuum spectrum includes 729 nm component is generated via launching the compressed pulses into a section of highly nonlinear PCF.Then,the phase noise induced by the fiber is compensated by a phase-locking circuit.The frequency extending amount caused by the phase noise of fiber with a length of 50 m is about 100 m Hz while the phase-locking circuit in closed loop state.Finally,we use the 250 MHz Yb-doped fiber optical frequency comb to measure the absolute frequency of the 729 nm ultra-stable laser,and a beat signal with a SNR of about 10 d B is detected preliminarily.6.In order to improve the average power of the fiber optical frequency comb,the femtosecond fiber amplifier with a high repetition rate is studied.Firstly,we build an Yb-doped fiber oscillator based on the NPR mode-locked principle,self-similar pulses are obtained while the net dispersion is about +4000 fs2 with a repetition rate of 49.5 MHz.Then using the self-similar mode-locked fiber oscillator as a seed source,we construct an all polarization-maintaining fiber femtosecond amplifier based on the CPA technique.After two-stage amplification and compression,the average power of de-chirped pulses is 3 W with the shortest duration of 101 fs.