Investigation Of Dual-wavelength Single-frequency Fiber Lasers

Dual-wavelength single-frequency fiber lasers have been extensively studied because of their special applications in microwave generation, fiber communication systems and optical fiber sensors due to their advantages of simple construction, low phase noise, narrow linewidth and tunability. The main content of the thesis is listed as below:1. The operation principle and basic structure of fiber lasers and single-frequency lasers are introduced.2. A dual-wavelength single-frequency fiber laser with switchable wavelength spacing based on two cascaded Fabry Pérot laser diodes(FP-LDs) and a Wave Shaper is proposed and demonstrated. The Wave Shaper performs the dual-wavelength selection. Injection locking of the FP-LDs and narrow bandwidth filtering effect of the Wave Shaper guarantee singlefrequency operation of the laser. By appropriately adjustment of the drive currents of the two FP-LDs and the filtering characteristic of the Wave Shaper, dual-wavelength single-frequency laser output with wavelength spacing switched among about 0.24 nm、0.40 nm、0.60 nm and 0.80 nm can be obtained. Each wavelength has a linewidth <16.5 k Hz and a side-mode suppression ratio(SMSR)> 50 d B.3. A dual-wavelength single-frequency fiber laser with switchable wavelength spacing based on graphene saturable absorber(GSA) and a Wave Shaper is proposed and demonstrated. The Wave Shaper performs the dual-wavelength selection, along with the excellent saturable absorption ability of graphene, the linewidths of the lasing wavelengths could be effectively reduced and eventually single-frequency operation can be obtained. By appropriately adjustment of the filtering characteristic of the Wave Shaper, dual-wavelength singlefrequency laser output with wavelength spacing switched among about 0.33 nm、0.50 nm、0.70 nm and 0.92 nm can be obtained. Each wavelength has a linewidth < 7.3 k Hz and a SMSR > 50 d B.