Single-longitudinal-mode Pulsed Fiber Laser And Its Applications In Mid-infrared Fiber Optical Parametric Oscillator

Due to the high peak power and narrow linewidth,single-longitudinal-ode pulse have been used widely in ladar,nonlinear wavelength conversion and remote sensing.Mid-infrared lasers also attract lots of attention for it has a good prospect.By using the single-longitudinal-mode pulse as the pump,fiber optical parametric oscillator is a proper way to obtain mid-infrared laser.In this paper,a single-longitudinal-mode cw fiber laser is developed,then single-longitudinal-mode pulse is obtained via injection locking technique,and the output power is boosted by multi-stage amplifiers.Through analyzing the theory of degenerate foxur-wave-mixing for large frequency shift,it is found that the single-longitudinal-mode pulse obtained above can fit the pump requirements well.Then a three-hole suspended-core chalcogenide fiber suitable for mid-infrared fibe optical parametric oscillator is designed,the performance of mid-infrared fiber optical parametric oscillator ultilizing chalcogenide fiber is analyzed.The main content is listed as follows:By combining fiber Lyot filter and saturable absorber in a ytterbium doped fiber laser,single longitudinal mode is achieved in a 31 nm tuning range from 1045 nm to 1076 nmn the linewidth is measured to be 3.6 kHz via the self-homodyne method.Then a tunable single-longitudinal-mode ytterbium doped fiber laser based on fiber grating is also analyzed,the tuning range is 3 nm,the linewidth is 2.6 kHz and it is very stable.The single-longitudinal-mode ytterbium doped fiber laser with fiber grating is used as the seed,after it is been injected into an actively Q-switched laser,single-longitudinal-mode pulse is achieved.Then using the multi-stage amplifiers to boost the output power,through optimizing the parameters of amplifier to avoid stimulated Brillouin scattering and noise of amplified spontaneous emission,the final single-longitudinal-mode pulse have repetition rate of 1 kHz,pulse width of 349 ns,peak power of 252.7 W,single noise ration larger than 20 dB and linewidth less than 0.03 nm.Based on the theory of degenerate four-wave-mixing for large frequency shift,and using the photonic crystal fiber LMA8 as an example,the pump requirements for linewidth,peak power and pulse width in the mid-infrared fiber optical parametric oscillator is numerically analyzed.It is found that the single-longitudinal-mode pulse obtained above can fit the requirements well.Then a three-hole suspended-core chalcogenide fiber is designed,by applying the single-longitudinal-mode pulsed thulium doped fiber laser as the pump,the converted light covering 2-5?m can be achieved.Using the numerical model for fiber optical parametric oscillator,the peformence of mid-infrared fiber optical parametric oscillator ultilizing chalcogenide fiber is analyzed,it reveals that a pump threshold power as low 0.21 W and a high conversion efficiency of 19%can be realized.