Over Octave-Spanning Supercontinuum Generation in Tapered Seven-Core Photonic Crystal Fiber

Broadband supercontinuum (SC) spanning more than an octave was obtained in tapered seven-core photonic crystal fibers (PCFs) upon pumping with a 150-fs mode-locked fiber laser. The appearance of the second zero dispersion wavelength in the tapered section of the PCF limited the solitons´ self-frequency shift. The simulations and experiments suggested that the unique group velocity in the tapered section could change the relative velocity of different spectral components, which resulted in some compression of the pulse in the time domain. It can be found that the spectral defects between the solitons were leveled up, and the visible region was enhanced remarkably, which was beneficial to control the SC generation. In addition, the interference fringes in the far field indicated the good spatial coherence of the output SC of the seven-core PCF.