Precision Control Of Optical Frequency And Optical Frequency Synthesis

Six years ago, optical frequency combs based on femtosecond Kerr-lens mode-locked lasers were introduced into the field of optical frequency metrology by merging ultra-fast (in the time domain) and ultra-stable (in the frequency domain) techniques, which realized the precise control of the electric field of lasers both in the time domain and in the frequency domain, and have firmly established their role in ultra-precise and ultra-fast physics. This thesis presents theoretical analysis and experimental work in precision optical frequency control of both ultra-fast lasers and continuous wave lasers.Toward the former, the basic principle of femtosecond Kerr-lens mode-locked lasers is firstly introduced. Then the pulse train emitted by a mode-locked laser in the time domain and the corresponding spectrum in the frequency domain are analyzed. And several control techniques of repetition rate f_r and offset frequency f_ceo of mode-locked lasers are also introduced in this dissertation. The special characteristics of mode-locked lasers as well as unique control of f_r and f_ceo enable us to make a connection and frequency transfer between microwave and optical frequencies. Experimentally, we present a novel configuration for the self-referencing technique, which is used for the control of offset frequency (or carrier-envelope phase in the time domain), named "collinear self-referencing set-up". The power utility of this simplified set-up has been proved to be reliable for controlling the f_ceo or the absolute phase of femtosecond mode-locked lasers. Besides, I also analyze the influence of different parameters of photonic crystal fiber and the pump laser for continuum generation. Several steps improving the long-term stability of femtosecond Kerr-lens mode-locked lasers are also discussed.As far as the frequency stabilization of continuous wave lasers is concerned, taking advantage of the traditional modulation transfer spectroscopy we have measured the hyperfine transitions of I₂ at about 532 nm, using a diode laser pumped a solid state Nd:YAG laser as the light source. The fairly good S/N ratio promises high precision of optical frequency stabilization of the laser. Lastly, I present a systematic analysis of ultra-sensitive detection methods based on frequency modulation spectroscopy towards the improvement of the limiting attainable performance by the choice of several parameters.And the future work and application of both ultra-fast lasers and continuous wavelasers are discussed.