摘要： The development of compact bright supercontinuum (SC) sources is of particular interest, especially in the mid-IR where is a lack of suitable sources [1,2]. Here we report first results on SC generation in a As2S3-silica dual nanospike waveguide [3, 4] pumped in different multi-pulse regimes by a high-power femtosecond Tm-doped fiber laser mode-locked by nonlinear polarization evolution [5-7]. The experimental set-up is sketched in Fig. 1a. The central wavelength of the laser is 1890 nm and its repetition rate is 13 MHz. By tuning the polarization controllers (PC1 and PC2) in the ring cavity [8], the laser could be configured to operate in different multi-pulse regimes, namely noise-like pulses, soliton bunches and soliton “rain”. The pulse duration is 931 fs in both soliton regimes. The coherence time of the noise-like pulses is 228 fs. The pulses were free-space launched into the As2S3-silica dual nanospike waveguide designed to improve the launch efficiency in and out of the waveguide (~20%). The central uniform portion of the hybrid nanospike has a core diameter of 1.1 μm, the group velocity dispersion (GVD) curve of which is plotted in the inset of Fig. 1a. The pump wavelength is in the anomalous dispersion region between two zero dispersion wavelengths. The measured SC spectra are shown in Fig. 1b for the regimes of soliton bunches (top) and noise-like pulses (bottom). The results from the soliton “rain” regime (not shown here) and the soliton bunches regime are similar. In the soliton regime, sidebands originating from self-phase modulation are observed for a launched peak power of ~90 W, with the spectrum spanning from 1650 nm to 2200 nm. The launched peak power of the solitons was estimated by the pulse duration and the laser characteristics after taking into account the coupling efficiency. The black-dashed line in Fig. 1b plots the simulated spectrum at the output end of the dual nanospike, agreeing reasonably well with experiment. In the preliminary simulation, a single pulse with the same peak power (90 W) was launched into the model. When pumping the waveguide by noise-like pulses the spectrum barely broadens, probably due to the smaller peak power of a single pulse in the packet. In summary, we have achieved spectral broadening in a As2S3-silica hybrid waveguide pumped in different multi-pulse regimes at 1890 nm. It appears that soliton-like regimes are preferable for SC generation. The system is promising for realizing all-fiber broadband SC sources using well-defined femtosecond pulses, as well as investigating different mechanisms of SC generation in multi-pulse regimes.