Study Of Ultra-wideband Wavelength-tunable Pulsed Laser At 2 μm

Lasers working in the nominally eye-safe 2 μm region(1.6 – 2.2 μm)have attracted significant attention due to their wide range of applications in,for example,optical communications,remote sensing,material processing,medicine,as well as nonlinear frequency.The fiber laser which can cover 2 μm has become the most significant goal in this field.The thulium-doped fiber laser(TDFL)is a promising candidate for achieving wideband tunable laser operation.For many of the aforementioned applications,a widely tunable source working in the pulsed regime is required or highly desired due to the flexibility in operation wavelength and temporal characteristics it can provide.Base on this,tunable TDFL can provide large convience on applications.If the laser structure by all-fiber device,it the applications and stablity will improve sharply.Pulsed operation of tunable TDFLs has also been reported,however,the technology is less well developed compared with its CW counterpart with only a limited number of demonstrations.By utilizing such a tunable filter,we build an cavity with widely tuning range of wavelength,approximately 290 nm(from 1765-2055 nm).The most narrow pulse width has been 97.48 ns.To the best of our knowledge the broadest tuning of a gain-switched fiber laser,while generating stable single nanosecond-scale pulses with a selectable repetition and pump power.1.The research background of wavelength-tunable fiber lasers at 2 μm is introduced.According to the pump power of the gain fiber used in laser,the developments of wavelength-tunable contiune wave and pulse fiber lasers at 2 μm are reviewed.The development trend of wavelength-tunable lasers at 2 μm is analysed.2.We demonstrate an theoretical model abouttunable gain-switched TDFL,and analyzing pump peak power,repetition rate,pump pulse width,cavity length,TDF length and coupling ratio which play an important role on the TDFL.It provide a guide to the experiments.3.We presented an all-fiber pulse Tm-doped laser with tunable wavelength from 1800 nm to 2000 nm.The tuning range almost arrive at 290 nm.The most narrow pulse width has been 97.48 ns.To best of our knowledge,this is the broadest tuning range that has been reported for an all-fiber.