Research On 2 ?m Erbium-doped Pulsed Fiber Laser Based On Synchronous Pump Mode-locking Technology

2 ?m ultrafast erbium-doped fiber lasers are used in a wide range of industrial and basic research fields such as laser medical,laser processing,laser radar,and optical frequency comb and mid-infrared supercontinuum generation.Therefore,the research of high stability 2 ?m ultrafast erbium-doped fiber laser has important academic significance and practical application value.Synchronous pump-mode-locking technology has been used for the generation of ultrashort pulses in early dye lasers.In the field of active fiber lasers,there has been little research on mode-locked pulse generation based on synchronous pumping technology.In this paper,synchronous pump-mode-locking technology is applied to erbium-doped fiber lasers to achieve the generation of 2 ?m ultrafast pulses with high system stability.The specific research work is as follows:1)The research status and application of 2 ?m pulsed erbium-doped fiber laser are summarized.The advantages of ultrafast erbium-doped fiber laser are pointed out,and the main research contents and innovations of this paper are expounded.2)The energy level structure and spectral characteristics of Tm3+ are analyzed.The basic principle and characteristics of 2 ?m mode-locked erbium-doped fiber laser are introduced.3)A 1.5 ?m nanosecond pulsed fiber laser and a pulse width adjustable 1.5?m picosecond pulsed fiber laser as a synchronous pump source for erbium-doped pulsed fiber lasers were developed.The pulse width of the nanosecond pulse source based on electric pulse modulation is 2.2-9.6 ns,and the repetitive frequency is tunable at 1-70 MHz;the pulse mode based on passive mode-locked picosecond pulse source is continuously adjustable at 2.5-3.8 ps,in the seed laser The output is connected to a 70 m dispersion-compensating fiber tospread the pulse width to 30 ps.4)Synchronously pumped 2 ?m ring cavity erbium-doped fiber lasers using the above 1.5 ?m nanosecond and picosecond fiber lasers.The system studied different pump parameters(pulse width,repetition rate,2 ?m intracavity dispersion)to 2 ?m.The effect of synchronous pumping mode-locked pulses.When using a 1.5 ?m nanosecond laser as the pump source,the 2 ?m synchronous pump mode-locked pulse width increases with a 1.5 ?m pump pulse width and the pulse width is less than 1.5 ?m pump pulse width;2 ?m synchronous pump lock The modulo RF signal-to-noise ratio increases slightly with 1.5 ?m pump power.The 2 ?m hybrid mode-locked pulse width is maintained at 1.1 ps with a 1.5 ?m pump pulse width.In the 10 MHz fundamental frequency synchronization,the center wavelength of the 2 ?m synchronous pump mode-locked mode spectrum can be seen to drift from 1919.2 nm to 1929.0 nm within a cavity detuning range of 1.95 mm.Using a 1.5 ?m picosecond laser with a repetitive frequency of 21.54 MHz as the pump source,a 1950 nm fundamental frequency synchronous pumped mode-locked pulse with a pulse width of 4.6 ps,a spectral width of 0.24 nm and a signal-to-noise ratio of 55 d B was obtained;It has a width of 2.655 ps,a spectral width of 2.93 nm,a signal-to-noise ratio of 60 d B,and a 1945 nm fourth-order harmonically pumped mode-locked pulse with a re-frequency of 21.54 MHz.The results show that the 2 ?m synchronous pump mode-locking is affected by pump pulse width,repetitive frequency and 2 ?m cavity dispersion,and can realize the fundamental frequency synchronous pump mode-locking and the far-reaching traditional synchronous mode-locking re-frequency limit.Fourth harmonic synchronous pump mode-locking.5)Using the developed 1.5 ?m picosecond fiber laser as the pump source,a2 ?m synchronous pump-passive mode-locked mode-locked fiber laser was studied,and a 2 ?m ultrashort hybrid mode-locked pulse with a pulse width of880 fs was obtained.The stable mode-locking power range is 167~238 m W,the corresponding output power is 0.4~7.8 m W,and the signal-to-noise ratio is up to63 d B.The system comparison study of 2 ?m passive mode-locking,synchronous pump mode-locking and hybrid mode-locking pulse laser shows that compared with synchronous pumping technology,hybrid mode-locking technology can not only maintain high system stability,but also achieve more Short mode-locking pulse width;compared with passive mode-locking technology,hybrid mode-locking can not only maintain a shorter mode-locking pulse width,but also achieve higher noise-to-noise ratio,lower clamping mode threshold,and better system stability.