Study On Mode-locking Of Saturable Absorbers With Fiber Single-mode-coreless-multimode-single-mode Structure

Mode-locked fiber lasers can be used in areas such as spectrometry,communication systems,laser processing,terahertz wave generation,etc.,or directly as seed light to other optical systems.In passive mode-locked fiber lasers,the search for new saturable absorbers to achieve higher quality laser output is an important research direction.In this paper,the theoretical principle and approximate model of the fiber-optic single-mode-coreless-multimode-single-mode structure as the saturable absorber are analyzed.It is experimentally proved that it is feasible to use the structure as a saturable absorber.More experiments were conducted with this saturable absorber to explore the lock mode of the structure.The main research work of this paper is as follows:1.Summary of the development history of lasers,the characteristics and applications of mode-locked fiber lasers.2.Introduced the basic principle of the laser and the main characteristics of the saturable absorber and the.mode-locked laser.3.Introduced the theoretical analysis of single-mode-multimode-single-mode fiber structure,and reasonably proposed a simplified model of optical transmission in fiber single-mode-coreless-multimode-single-mode structure,and verified the structure could be used as an saturable absorber and the structure has filtering capability by experiments.4.The structure is used as a saturable absorber for mode-locking,and tunable and dual-wavelength mode-locked output is realized.5.The positive dispersion mode-locking and the line cavity mode-locking are respectively performed by the structure,and the pulse output of the rectangular spectrum and the high peak power is obtained respectively.