Single-cavity dual-modelocked 2.36-µm laser

Area of Science:

• Laser Physics
• Optical Engineering
• Mid-Infrared Spectroscopy

Background:

• Dual-comb spectroscopy offers precise molecular fingerprinting but is typically limited to near-infrared wavelengths.
• Developing compact, free-running dual-comb sources operating at longer wavelengths is crucial for expanding applications.

Purpose of the Study:

• To demonstrate the first dual-modelocked femtosecond laser oscillator operating beyond 2 µm.
• To investigate the performance characteristics of this novel laser system for potential dual-comb applications.

Main Methods:

• Utilized a Cr:ZnS crystal as the gain medium for mid-infrared emission.
• Employed an InGaSb semiconductor saturable absorber mirror (SESAM) for stable modelocking.
• Incorporated a two-surface reflective device for spatial duplexing of the two pulse trains (combs).

Main Results:

• Achieved stable dual-modelocked operation at 2.36 µm with a repetition rate of 242 MHz.
• Generated two distinct pulse combs, each with a 30 nm spectral bandwidth and ~200 fs pulse duration.
• Obtained an average output power exceeding 200 mW per comb with a repetition rate difference of 4.17 kHz.
• Demonstrated stable modelocking across a wide range of output powers.

Conclusions:

• This work presents a significant advancement in mid-infrared laser technology.
• The developed laser is a promising platform for realizing compact, free-running dual-comb spectroscopy systems beyond 2 µm.
• This opens new avenues for molecular detection and analysis in the mid-infrared spectral region.