Development And Application Of High Precision Optical Fiber Frequency Comb

Due to its wide spectrum and narrow linewidth,femtosecond optical frequency comb can improve the frequency measurement accuracy to the order of 10-19,which greatly enhances the ability of human beings to explore the microscopic world and scientific laws.And furthermore,the optical frequency comb provides an excellent measuring method with high-precision,high-accuracy and high-sensitivity for multiple research fields,such as precise spectroscopy,calibration of basic physical quantities,optical clocks,attosecond science and astronomical observation.This dissertation aims at developing field-applicable,high-precision fiber frequency combs.To develop practicable frequency combs,four phases of work including innovation of comb phaselocking method,researches of key technologies for field-applicable frequency comb,verification of the practical performance of frequency comb and principle exploration of more integrated dual-comb source are carried out.Through the joint adjustment and optimization of optical path,circuitry,machinery and program design,a fieldapplicable,high-precision fiber frequency comb with low noise,low power consumption,high integration and high stability is eventually achieved.During the research,several key techniques have been developed and the details are summarized as follows:1.The innovation of the frequency comb phase-locking technology is carried out.A new method that uses the electrical polarization controller(EPC)for fceo phaselocking is developed.Compared with pump modulation,EPC modulation has the advantages of higher bandwidth,larger gain,and smaller fr/fceo crosstalk.Furthermore,the power and intensity fluctuations that EPC approach introduced is only 1/2 and 1/20 of that the pump modulation introduced.Benefit from the excellent repeatability and stability of EPC,the mode-locked states can be fast recovered according to the prior collection of the polarization settings,which can effectively reduce the buildup time of low-noise frequency comb.2.Researches on key technologies for spaceborne frequency combs are carried out.During the research,a number of technical difficulties have been overcome.a)To meet the strict requirements for the applications in filed or even space environment,we have optimized the optical path,circuitry,mechanical design and programme of the frequency comb.A frequency comb with lownoise,low power-consumption,high integration and high-stability is realized.The integrated fiber comb can operate stably for days in outdoor environment and withstand the risks of transportation between cities.b)We studied the methods for pulse noise suppression and the stability of the frequency comb has been improved by changing the phase-locking loop from low feedback bandwidth to high feedback bandwidth and changing the external reference from microwave to optical frequency.The stability of the fr signal is improved to 1.24×10-13 when referencing to the microwave frequency and the tracking accuracy of the frequency comb can be improved to 5.19×10-17 when referencing to the optical frequency.3.The practical performance of the optical comb has been tested.A dual-comb spectroscopy detection equipment is built by using two integrated fiber frequency combs for quantitative analysis of characteristic gases in leak detection of power equipment.The precise frequency control and fine temperature control allow the combs to maintain high coherence within more than 2 hours in outdoor operation.In terms of spectral detection,the mixture of CO and CO2 was measured and as a result,the absorption peaks of CO and CO2 within 1540-1590 nm band are simultaneously measured on ms time scale.The molecular densities of CO and CO2 could be easily derived from Lorentzian fitting,and the multimodal measurement uncertainties are reduced to 0.32% and 0.24%,respectively.4.The dual-comb spectroscopy detection equipment based on two frequency combs is accompanied with the problems of huge size,high cost and complex system.Therefore,we have carried out principle exploration and application research on a more integrated dual-comb source.Through theoretical simulation,we reveal the complete dynamic process of the dual-wavelength laser with net-normal dispersion from noise to stable dual-wavelength mode-locking for the first time and found that the dispersion induced pulse collision is a key catalyst for the transformation of single-wavelength mode-locking to dual-wavelength modelocking.Then,the simulation conclusion is verified by establishing a NALMbased,all polarization-maintaining dual-wavelenth mode-locked laser and observing its complete buildup process with the help of the time-stretching dispersive Fourier transform technology.Finally,the output of the single-cavity dual-wavelength laser is converted into the mid-infrared band and its potential in spectroscopy has been verified,which can provide a implementable source for multi-band,high-precision spectral measurements.