Octave-spanning single-cycle middle-infrared generation through optical parametric amplification in LiGaS₂

Area of Science:

• Laser Physics
• Nonlinear Optics
• Spectroscopy

Background:

• Generating broadband, phase-locked mid-infrared (mid-IR) pulses is crucial for advanced spectroscopic techniques.
• Existing methods often face limitations in bandwidth, phase stability, or complexity.

Purpose of the Study:

• To develop a robust method for generating extremely broadband and inherently phase-locked mid-IR pulses.
• To achieve pulse generation covering the 5 to 11 µm spectral region.

Main Methods:

• Utilized a two-stage optical parametric amplification (OPA) process.
• Employed a 270-fs Ytterbium-doped potassium gadolinium tungstate (Yb:KGW) laser source.
• Used beta-barium borate (BBO) for a continuum-seeded, second-harmonic pumped pre-amplifier and lithium gallium disulfide (LGS) for mid-IR generation and amplification, managing bandwidth and chirp with optical filters and bulk materials.

Main Results:

• Successfully generated mid-IR pulses with a spectrum smoothly covering 5-11 µm.
• Achieved a quantum efficiency of 1% with pulse energy of 220 nJ at a 50 kHz repetition rate.
• Characterized near-single-cycle mid-IR pulses (32 fs) with passively stable carrier-envelope phase using electro-optic sampling.

Conclusions:

• The developed two-stage OPA system provides a reliable method for generating broadband, phase-locked mid-IR pulses.
• These pulses are well-suited for applications such as generating attosecond electron pulses and advancing molecular fingerprint spectroscopy.