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[摘要]：Broadband mid-infrared supercontinuum pulses were generated directly from a short piece of active fiber in a single-mode Tm-doped fiber amplifier. The broadband mid-infrared pulses have an extremely high spectral flatness with similar to 600 nm FWHM bandwidth (from 1.9 mu m to 2.5 mu m), >15 kW peak power, and >20 GW/cm(2) laser peak intensity. This new approach exhibits a significantly different physical mechanism from other supercontinuum generation demonstrations in the literature, in which usually a piece of passive fiber was used for nonlinear spectral broadening. The physical mechanism for the broadband mid-infrared supercontinuum generation in this approach has been attributed to a combined effect of two superradiative processes of Tm3+ ions (i.e., the F-3(4) - H-3(6) transition covering the 1.8 similar to 2.1 mu m spectral region and the H-3(4) - H-3(5) transition covering the 2.2 similar to 2.5 mu m spectral region), and also nonlinear optical processes as well in the Tm-doped gain fiber. The spectra of the mid-infrared supercontinuum pulses were further broadened in a 2 m chalcogenide fiber with 20 dB bandwidth similar to 1100 nm and a 3 m fluoride fiber with 20 dB bandwidth similar to 2600 nm. (C) 2012 Optical Society of America |
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