High-power frequency comb source tunable from 2.7 to 4.2 {\mu}m based on difference frequency generation pumped by an Yb-doped fiber laser

摘要

We demonstrate a broadband mid-infrared (MIR) frequency comb source based ondifference frequency generation (DFG) in periodically poled lithium niobate(PPLN) crystal. Mid-infrared radiation is obtained via mixing of the output ofa 125 MHz repetition rate Yb-doped fiber laser with Raman-shifted solitonsgenerated from the same source in a highly nonlinear fiber. The resulting idleris tunable in the range of 2.7 - 4.2 {\mu}m with average output power reaching237 mW, and pulses as short as 115 fs. The coherence of the MIR comb isconfirmed by spectral interferometry and heterodyne beat measurements.Applicability of the developed DFG source for laser spectroscopy isdemonstrated by measuring absorption spectrum of acetylene at 3.0 - 3.1 {\mu}m.