Broadband optical supercontinuum generation using low-cost multimode 975-nm pump lasers

摘要

Broadband laser sources are very attractive for optical communications and technologies requiring low-coherence laser sources. The supercontinuum (SC) is generated by ultra-short pulsed or continuous wave (CW) lasers that are injected into fibers with high nonlinearity. Mode-locked lasers and Raman fiber lasers are generally used in the two pumping regimes. Pumping with 975-nm multimode laser diode is considered a low cost technology in the CW regime. However, it has not been well investigated. This thesis studies the SC generation process using low-cost 975-nm multimode laser diodes, a piece of Erbium/Ytterbium co-doped fiber (EYDF) and two units of highly nonlinear fibers (HNLFs) with different dispersion properties around 1550nm wavelengths. Three broadband and high optical power SCs extending to 2000nm wavelength are successfully generated, one in ring and two in single-line structure. To our knowledge, they are the broadest SCs using this low cost technology. In addition, one of the two SCs in the single-line structure even covers a wavelength range from 1200nm to more than 2000nm by getting rid of the band limit of splitter. Moreover, the key role of four-wave mixing (FWM) in the broadness and flatness of CW pumped SC are demonstrated. The demonstration is more evident than previous works and convergence is obtained in the two pumping regimes on the importance of FWM in SC generation. Our designs realize fiber laser sources with high power, broad bandwidth and reduced cost.