Novel Tunable Single-longitudinal-mode Fiber Lasers

Laser has been attracted much interest Since Theodore Harold Maiman successfully made the first ruby laser in 1960,and the type of laer is increasing.With the development of laser technology,the role played in the manufacturing industry,medical technology,national defense technology and et al.is becoming more and more important.Among them,the single longitudinal mode(SLM)laser is widely used in laser radar,laser ranging,laser remote sensing,optical communication,optical sensing,holographic imaging,medical laser,high resolution spectroscopy and optical frequency standard et al.for its' better beam quality,longer coherence length,narrower width of the spectral line.The thesis is based on some novel technology of tunable SLM fiber laser,as listed as below:1.A new kind of tunable SLM fiber laser based on IFWM effect is proposed.Inverse fourwave mixing effect is a nonlinear self-action effect,self-parametric amplification(SPA),which manifests itself as optical spectrum narrowing in a negative dispersion.In two experiments,a 5 km dispersion shifted fiber(DSF)and a nonlinear semiconductor optical amplifier(NL-SOA)is added in the cavity respectively as negative dispersion to realize the narrowing of linewidth.After many cycles,a stable laser operating mechanism is formed in the cavity,and the output of a SLM laser is obtained.In the experiment of SLM laser based on DSF,a continuous tunable SLM laser output in the range of 1534.96 nm to 1570.02 nm is realized.The linewidth is less than 6.5 k Hz,and the side mode suppression ratio(SMSR)is more than 65 d B.Because of a comb optical filter(COF)was inserted in experimental setup of the SLM laser based on the NL-SOA,a continuous tunable dualwavelength SLM laser output with a wavelength spacing of 0.4 nm is achieved in a range of 1530 nm to 1586 nm.The linewidth is less than 8 k Hz,and the SMSR is more than 40 d B.2.By employing a silicon micro ring resonator(SMRR)in the cavity,the SLM output is realized because of the narrowest channel of the micro ring.In the experiment,a SLM laser output with a tunable range of 1538 nm to 1583 nm is achieved.The SMSR is more than 50 d B,and the linewidth is less than 7 k Hz.3.A chirped fiber Bragg grating(CFBG)is used to construct a sub-cavity,so that the light can run along different optical paths,which is equivalent to multi-sub-cavity.This construction can improve free spectral range(FSR)effectively.In the experiment,a tunable optical filter(TOF)is employed in the cavity.As a result,a SLM laser output with a tunable range of 1535 nm to 1565 nm is achieved,which linewidth is less than 8.5 k Hz and SMSR is more than 50 d B.