Spectrum-Flexible Green Light Source Based on SC-PPLN and Superfluorescent Fiber Source

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.