Beam combining of a broadly and continuously tunable quantum cascade laser

Area of Science:

• Optics and Photonics
• Quantum Electronics
• Spectroscopy

Background:

• Quantum cascade lasers (QCLs) are crucial for mid-infrared (mid-IR) applications.
• Efficient beam combining is essential for enhancing the power and functionality of laser arrays.
• Mid-IR gas sensing offers high sensitivity for detecting various molecules.

Purpose of the Study:

• To develop and demonstrate a cost-efficient method for combining beams from an array of mid-IR tunable slot waveguide quantum cascade lasers.
• To achieve high coupling efficiency for gas sensing applications.
• To validate the combined beam's utility for simultaneous detection of multiple gases.

Main Methods:

• Utilized an array of five tunable slot waveguide quantum cascade lasers operating around 10 µm.
• Employed an aspherical lens with five mini mirrors for individual beam collimation and combining.
• Coupled the combined beams into a low numerical aperture (N.A. = 0.03) hollow-core fiber gas cell.

Main Results:

• Successfully demonstrated beam combining of five mid-IR laser elements.
• Achieved a high coupling efficiency of >= 0.82 into the hollow-core fiber.
• Verified the feasibility for simultaneous gas sensing of ammonia and ethylene.

Conclusions:

• The proposed beam combining method is cost-efficient and effective for mid-IR laser arrays.
• High coupling efficiency into a low N.A. fiber is achievable.
• This technique is suitable for sensitive and simultaneous gas detection applications.