Research On 2.1?m Thulium-doped Fiber Laser And Dual-comb Mode-locked Fiber Laser

In this thesis,two kinds of innovative fiber lasers were investigated.The first one is a continuously tunable thulium(Tm)-doped fiber laser(TDFL)operating in the important 2.1?m region,which is particularly tandem-pumped by a 1908 nm laser source.The second one is polarization-multiplexed dual-come fiber laser,which is based on nonlinear amplifying loop mirror(NALM)mode-locking mechanism.Benefit from the allpolarization-maintaining design,the two frequency combs have high stability and long-term operation reliability.More importantly,the setups can be significantly simplify and common mode noise can be suppressed.The main content includes:(1)By numerical simulation,the advantages containing parasitic lasing suppression,signal-to-noise ratio(SNR)improvement and long wavelength operation beyond 2.1?m of the innovative pump method were proved theoretically.(2)After the tandem-pumped TDFL was constructed,a wavelength-tuning range of 2000-2172 nm was achieved.Over the full wavelength-tuning range,an optical SNR of more than 30 d B was measured.At central wavelengths of 2050 nm and 2172 nm,the slope efficiencies were 23% and 9.9%,respectively.(3)By numerical simulation,it is approved that appropriate splitting ratio,longer polarization-maintaining fiber and higher pump power within limits are benefit to selfstart mode-locking.(4)The NALM dual-comb fiber laser with overlapping spectra was constructed.The dual mode-locking pulses were obtained at the repetition frequency of 34.68 MHz around1563 nm.The minimum tunable frequency difference is about 230 Hz.