Active mode locking of quantum cascade lasers in an external ring cavity.

Area of Science:

• Photonics
• Laser Technology
• Spectroscopy

Background:

• Mode-locked lasers generate ultrashort light pulses and frequency combs for applications in spectroscopy, chemical detection, and ultrafast process studies.
• Compact mode-locked lasers are prevalent in visible and near-infrared ranges, but mid-infrared counterparts are typically bulky, expensive, and rely on nonlinear frequency conversion.
• Quantum cascade lasers (QCLs) are powerful compact mid-infrared sources, but achieving mode-locked operation has been a significant challenge.

Purpose of the Study:

• To demonstrate active mode locking in an external-cavity quantum cascade laser.
• To develop a compact and versatile mid-infrared light source for various scientific applications.

Main Methods:

• Utilized an external-cavity design for a quantum cascade laser.
• Implemented active mode-locking techniques.
• Operated the laser at room temperature across a full range of injection currents.

Main Results:

• Successfully demonstrated active mode locking in an external-cavity quantum cascade laser.
• Achieved stable ultrashort light pulse generation.
• Confirmed operation at room temperature and across the entire dynamic range of injection currents.

Conclusions:

• Active mode locking of external-cavity quantum cascade lasers is feasible.
• This development provides a compact, room-temperature mid-infrared light source.
• The demonstrated technology has potential applications in high-resolution spectroscopy and chemical detection.