Design And Investigation On 2 ?m Tm/Ho-codoped Fiber Laser Based On SESAM

2 ?m mode-locked fiber lasers are favored at home and abroad because of their low cost,simple structure and small size and they have application advantages in medical treatment and mid-infrared laser pumping.However,they still have some problems such as low average output power and slope efficiency.This dissertation centers around the subject,designing and analyzing the 2 ?m mode-locked Tm/Ho-codoped fiber lasers based on SESAM.It is of great significance and value to output 2 ?m pulse laser with high average output power and slope efficiency.And The main contents are as follows:Firstly,Based on the setting forth about research progress of 2 ?m mode-locked fiber lasers,the advantages and disadvantages for mode-locked technologies are introduced.The results show that the average output power and slope efficiency of 2 ?m mode-locked Tm/Ho-codoped fiber lasers are low.Thus,a 2 ?m mode-locked Tm/Ho-codoped fiber lasers based on SESAM is proposed.Then the fundamentals of Tm/Ho-codoped fiber laser based on SESAM is analyzed on the basis of the characteristics of Tm/Ho-codoped fiber,cavity and SESAM,which will provide theoretical basis for the design of a Tm/Ho-codoped fiber laser based on SESAM.Secondly,2 ?m linear cavity passively mode-locked Tm/Ho-codoped fiber laser based on SESAM with high average output power is designed.And pulse laser with a central wavelength of 1925 nm,a repetition frequency of 12.9 MHz,a pulse width of 18 ps,average output power of 89.62 mW,and a SNR of 55 dB is outputted.And the slope efficiency of the fiber laser is 10.6%.The instability of the average output power of the laser within 3 h is 0.225%.The fiber laser outputs high average output power when realizes the goals.However,the problem is that the slope efficiency of the output laser is low.Finally,in order to improve the slope efficiency,a mode-locked Tm/Ho-codoped fiber laser based on SESAM with a ring cavity is designed and set up.When the pump power is 650 mW,the central wavelengths of the laser are 1940.68 nm,2199.08 nm and2218.08 nm,respectively,and the repetition frequency is 7.09 MHz.The pulse width of the output laser is 56 ps,and the SNR is 60 dB.In addition,the central wavelength of the laser will move to a long wavelength as increasing the pump power,and the longest wavelength is 2226.40 nm.This is the first time that SESAM has been applied to a ringcavity Tm/Ho-codoped fiber lasers for mode-locking.Compared with the linear cavity mode-locked Tm/Ho-codoped fiber laser based on SESAM,the utilization of the pump laser has been improved.