Research On Tunable Active Mode-locked Fiber Laser Based On DMD

Mode-locked laser technology is an important means of generating ultra-short optical pulses with high repetition rate,and has important and extensive application value in many fields such as optical communication,optical sensing,ultrafast optics,optical signal processing,supercontinuum generation and laser processing.Because of the advantages of simple structure and adjustable pulse repetition frequency,active mode-locked fiber laser has become an important research direction in the field of laser mode-locking.Trying to develop an active mode-locked fiber laser that can be tuned for key technical indicators such as center wavelength,output pulse width,pulse repetition frequency,etc.will greatly expand the application scenarios and application fields of mode-locked fiber lasers,and is also a new generation of flexible grid(Grid Free)Dense wavelength division multiplexing(DWDM)optical communication system and all-optical time division multiplexing(OTDM)technology require effective light sources,which have important research significance and practical application value.In this paper,based on the theoretical and experimental research of the programmable micro-tunable device(DMD)tunable optical filter system,the tunable active mode-locked fiber laser based on the LiNbO3 modulator and DMD filter is deeply researched,and set up relevant experiment system.The main work of the paper is as follows:1.Based on the analysis of the basic principles of erbium-doped fiber(EDF)and active mode-locked fiber laser,the theory of active mode-locked fiber laser is established by applying the theory of traveling wave rate equation.2.Build an active mode-locked fiber laser based on LiNbO3 intensity modulator.When the 20th harmonic mode is locked,the repetition frequency is 219.42MHz,the pulse width is 4.99ps,the center wavelength of the mode-locked spectrum is 1564.1nm,and the 3dB bandwidth is 5.8 nm stable mode-locked laser output.The effects of different repetition frequencies on the laser wavelength and the average output power of the laser under different pumping conditions were also studied experimentally.3.Based on the analysis of the working principle and diffraction characteristics of DMD,and using ZEMAX software to simulate and analyze the tunable optical filter based on DMD,design and build a tunable optical filter system based on DMD,the experiment realized the filter High-precision independent tuning of center wavelength and filter bandwidth.4.A tunable active mode-locked fiber laser experimental system based on LiNbO3 modulator and DMD filter was built to achieve continuous tunable mode-locked laser output with a center wavelength in the range of 1526-1555nm and a total of 29nm,and the wavelength tuning accuracy was 0.06nm.At the center wavelength of 1537.95nm,when the modulation frequency is changed in the 6th and 53rd order mode locking,54.21MHz and 476.03MHz repetition frequency mode-locked pulse output is obtained,and the DMD is controlled to load different width pixel bars to change the filter bandwidth when 1.96nm and 2.94nm achieve laser output with mode-locked pulse widths of 17.53ps and 12.92ps.The experiment realized the tuning of the mode-locked center wavelength,pulse repetition frequency and pulse width.