Simple approach to broadband mid-infrared pulse generation with a mode-locked Yb-doped fiber laser

Broadband mid-infrared (MIR) molecular spectroscopy demands a bright and broadband light source in the molecular fingerprint region. To this end, intra-pulse difference frequency generation (IDFG) has shown excellent properties among various techniques. Although IDFG systems pumped with 1.5- or 2-mu m ultrashort pulsed lasers have been extensively developed, few systems have been demonstrated with 1-mu m lasers, which use bulky 100-W-class high-powerYbthin-disk lasers. In this work, we demonstrate a simple and robust approach of 1-mu m-pumped broadband IDFG with a conventional mode-locked Yb-doped fiber laser. We first generate 3.3-W, 12.1-fs ultrashort pulses at 50MHz by a simple combination of spectral broadening with a short single-mode fiber and pulse compression with chirped mirrors. Then, we use them for pumping a thin orientation-patterned gallium phosphide crystal, generating 1.2-mW broadband MIR pulses with the -20-dB bandwidth of 480 cm(-1) in the fingerprint region (760-1240 cm-1, 8.1-13.1 mu m). The 1-mu m-based IDFG system allows for additional generations of ultrashort pulses in the ultraviolet and visible regions, enabling, for example, 50-MHz-level high-repetition-rate vibrational sum-frequency generation spectroscopy or pump-probe spectroscopy. (C) 2022 Optica Publishing Group

Automated summary

This work demonstrates a simple and robust method of 1-mu m-pumped broadband IDFG for generating MIR pulses in the fingerprint region. The system also enables additional generations of ultrashort pulses in the ultraviolet and visible regions, showing potential for applications such as high-repetition-rate vibrational sum-frequency generation spectroscopy or pump-probe spectroscopy.