Visible-Near infrared Ultra-Flat supercontinuum generation in long tapered photonic crystal fibers

Abstract

In this study, an all-fiber ultra-flat supercontinuum (SC) was developed using tapered photonic crystal fibers (TPCFs). We analyzed the effects of taper ratio and taper length on SC generation. The results indicate that appropriate taper length and taper ratio can effectively enhance the bandwidth and flatness of the SC. A silica TPCF with a transition region of approximately 24 m was fabricated. When the TPCF’s length was 27.55 m (with a transition region of 14.55 m), we achieved an ultra-flat SC with a 3 −dB bandwidth of 1245 nm (ranging from 743 to 1988 nm), using 1-ps pump pulses at 1064 nm. This SC exhibited a cut-in wavelength of 384 nm and a spectral coverage extending over 1.55 octaves. To the best of our knowledge, the 3 −dB bandwidth of this SC spectrum represents the widest level ever reported for a silica fiber-based SC laser. Furthermore, in subsequent research, we numerically generated a ultra-flat broadband SC at a 3 −dB level from 433 to 2728 nm, using 10-ps pump pulses at 1064 nm, almost covering the transmission band of silica. This study demonstrates a method that significantly enhances the flatness of the SC output.