Photonic generation of tunable microwave signals from a dual-wavelength distributed-Bragg-reflector highly Er~(3+)/Yb~(3+) co-doped phosphate fiber laser

摘要

The photonic generation of tunable microwave signal from a dual-wavelength distributed-Bragg-reflector (DW-DBR) highly Er~(3+)/Yb~(3+) co-doped phosphate fiber laser is presented. Microwave signals centered at ～15, ～22 and ～25 GHz with < 10 kHz linewidth were obtained. The laser cavity of the fiber laser consists of a dual-channel narrowband fiber-Bragg-grating (DC-NB-FBG), a 0.4-cm-long Er~(3+)/Yb~(3+) co-doped phosphate fiber and a wideband FBG (WB-FBG). The wavelength selecting gratings are spatially separated to create partially separated resonant cavities. Er~(3+)/Yb~(3+) co-doped phosphate fiber ensures that mode competition is relative weak under low pump power. The short cavity length and the DC-NB-FBG ensure that only one longitudinal mode is supported by each reflection peak. Dual-wavelength single-frequency lasing with laser linewidths of <4 kHz is achieved.