Generation Of Dual Optical Frequency Comb Based On Mode-locked Fiber Laser And Its Applications

It is increasingly demanding for frequency accuracy in precision metrology field and other fields,and the traditional He-Ne laser based on iodine frequency standard with frequency accuracy of 10^-11 has failed to meet the requirement.The“state-of-the-art”developments in four distinct fields:ultrastable lasers,ultrafast pulse lasers,ultranonlinear materials and responses,and ultrasensitive laser spectroscopy promoted the emergence of high-performance“optical frequency comb”.The optical frequency comb,similar to a gearbox,builds a bridge between the radio frequency standard and optical frequency standards,with frequency accuracy of 10^-16,making it a powerful optical tool.With the development of optical frequency comb technology,“dual optical frequency comb”was put forward.It has been applied to spectrum analysis,absolute distance measurement and other research fields,improving the measurement performance of various fields to different degrees.Due to the important application value of dual optical frequency comb,the generation of dual optical frequency comb based on the mode-locked fiber laser and its application on ultrafast time-stretch microscopy are studied in this thesis.The main content of the thesis includes:?1?Two mode-locked fiber lasers based on the nonlinear polarization rotation effect,with nearly 92-MHz repetition rates,have been set up.?2?To stabilize the repetition rates of two mode-locked lasers to the same clock source,two sets of phase lock loop were built through some core devices such as mixer and PI controller.Dual-comb system with stable repetition rates and adjustable repetition frequency difference was achieved.?3?On the basis of exiting dual-comb system,the combination of dual-comb asynchronous optical sampling technique and ultrafast time-stretch microscopy has been proposed and demonstrated.Compared to the conventional time-stretch microscopy,the bandwidth requirement is relaxed by around 4 orders of magnitude.Besides,this method will widen the application areas of the time-stretch microscopy.?4?Aiming at the locking of the relative carrier envelope offset frequency of the dual optical frequency comb,the traditional relative frequency locking method based on continuous wave has been tried,and the relative frequency locking scheme based on stimulated brillouin scattering has been proposed.Some problems have been encountered and preliminary experimental results have been realized in both methods.