The green light source with tailorable temporal coherence has been widely applied in sensing, optical coherence tomography, speckle-free imaging, and partial coherent applications. In this paper, based on a tunable superfluorescent fiber source, we extend the ability of spectral regulation and temporal coherent tunability to the green light band through the second harmonic generation in a step-chirped periodically poled lithium niobate (SC-PPLN) crystal. The wavelength can be tuned from 517.2 nm to 540.0 nm, and the temporal coherence can be controlled by adjusting the bandwidth from 0.23 nm to 13.00 nm. Moreover, we further investigate the output performance at different temperatures and indicate that the appropriate operation wavelength and bandwidth contribute to better power stability under temperature variation. Our work may provide a flexible tunable source for optical coherence tomography, fluorescent imaging, spectroscopy, and so on.

In this paper, we demonstrate a narrow linewidth random fiber laser, which employs a tunable pump laser to select the operating wavelength for efficiency optimization, a narrow-band fiber Bragg grating (FBG) and a section of single mode fiber to construct a half-open cavity, and a circulator to separate pump light input and random lasing output. Spectral linewidth down to 42.31 GHz is achieved through filtering by the FBG. When 8.97 W pump light centered at the optimized wavelength 1036.5nm is launched into the half-open cavity, 1081.4 nm random lasing with the maximum output power of 2.15W is achieved, which is more powerful than the previous reported results.