The Reaserch And Applications Of The Coherent Dual-comb System

The dual-comb spectroscopy technology has technical advantages such as wide spectrum,high speed and high precision,and is an important means to carry out higher precision and faster spectrum measurement.After more than ten years of development,dual-comb spectroscopy technology has been initially applied in three-dimensional imaging,gas molecule analysis,velocity field and temperature field precision measurement,and has become a research hotspot in the field of optical measurement nowadays.The dual-comb spectroscopy technology uses optical heterodyne detection technology to convert the optical frequency comb teeth of the optical frequency comb into the radio frequency domain through beat frequency detection.The precision measurement of the optical frequency comb spectrum can be realized in the measurement time of the order ofμs～ms,and the spectrum measurement accuracy can be traced to the RF atomic clock standard.On the one hand,the ultra-low noise optical frequency comb is an important basis for realizing high-precision dual-comb spectroscopy.Therefore,the development of noise immunity technology and active phase noise control technology to improve the frequency stability and time stability of the optical frequency comb is to improve the dual The key process of optical frequency comb measurement accuracy.On the other hand,although the dual-comb system can meet many requirements for precision spectrum measurement,the current coherence time of the dual-comb system is still too short.This has become a key technical bottleneck for the application and development of dual-comb technology.A new type of phase control technology to produce a long-term high-coherence dual-comb system to meet the needs of higher precision spectrum measurement.This thesis would focus on the“The Reaserch and Applications of the Coherent Dual-comb System”.The phase control techniques of optical frequency comb with high reponse bandwidth are developed.Thus,a low-noise frequency comb source is achieved.After that,a highly coherent dual-comb spectroscopy is obtained and its locking accuracy has reached the world-class level.Finally,the application researches of molecular spectral measurement,precision ranging,imaging and gas velocity measurement are carried out based on the system.The specific research contents and innovations of this paper are summarized as follows:1.Developing a polarization-maintaining ultra-low noise optical frequency comb.A low-noise fiber laser is developed with well-self starting characteristics and high anti environmental noise ability.Then,the open-loop locking bandwidth of the optical frequency comb is increased from several k Hz to 166 k Hz combining with a variety of phase controllers,and the long-term stable operation of the optical frequency comb is realized.In the end,the stability of carrier envelope offset frequency of optical frequency comb is improved to 10^-19,and the corresponding integral phase noise is only 81.9 mrad（1 Hz to 1.5 MHz）.2.A highly coherent dual-comb system is achieved.The optical frequency transfer technology between optical frequency combs is studied to achieve the optical frequency control between multiple optical frequency combs.A highly coherent dual-comb system is obtained,whose frequency accuracy can be traced to the common hydrogen atomic clock.The results show that the stability of the repetition rates of the dual-comb system reaches 10^-12,the relative linewidth is less than 1 Hz,and the coherence time is up to 80 s.3.The applications of dual-comb spectroscopy in spectral measurement,ranging,microscopic imaging and gas velocity measurement were studied.The distance measurement and molecular absorption spectrum measurement are realized simultaneously by combining the time-of-flight method with and dual-comb spectroscopy technology,in which the spectral resolution is 100 MHz and the ranging accuracy in a measurement time of 0.5 s reachs to be 0.68μm.The multi-directional analysis of microstructure samples is realized via the combination of the spectral-encoding technology and dual-comb technology.The transverse accuracy is 4.4μm,and the longitudinal accuracy of gold film samples is 7.72 nm.Besides,the multi absorption peaks of gas molecules can be measured with high accuracy via the analysize of the spectral Doppler shift effect.Thus,the gas velocity can be obtained.These studies promote the development of the practical applications of dual-comb spectroscopy in many fields.4.A passively coherent single cavity dual-comb spectroscopy is developed.In this paper,a novel dual-pulse laser based on saturable absorption mirror is studied theoretically and experimentally with well passive coherence characteristics.The standard deviation of repetition rate difference is 83 m Hz with teeth-resolved spectra.