High power, broad tuning quantum cascade laser at λ ∼ 8.9 µm

Area of Science:

• Semiconductor Lasers
• Quantum Cascade Lasers
• Mid-Wave Infrared Technology

Background:

• Broadband absorption spectra of molecules in the mid-wave infrared (MWIR) necessitate broadly tunable lasers for comprehensive analysis.
• Existing tunable laser systems often struggle to cover the entire MWIR spectrum in a single scan, limiting their application scope.

Purpose of the Study:

• To report a novel strain-balanced InAlAs/InGaAs/InP quantum cascade laser (QCL) structure.
• To achieve high output power and a wide tuning range at approximately 8.9 µm for MWIR applications.

Main Methods:

• Fabrication of a strain-balanced InAlAs/InGaAs/InP QCL structure utilizing a diagonal transition active region.
• Characterization of laser performance, including pulsed and continuous wave (CW) output power, wall-plug efficiency, and external-cavity tuning range.

Main Results:

• Maximum pulsed optical power of 4 W and wall-plug efficiency of 11.7% at room temperature.
• Maximum CW double-facet power of 1.2 W at 25 °C for a 4 mm laser.
• External-cavity tuning range from 7.71 µm to 9.15 µm (pulsed) and 8 µm to 8.9 µm (CW).
• CW power exceeding 200 mW across the entire external-cavity spectrum.

Conclusions:

• The developed InAlAs/InGaAs/InP QCL demonstrates significant advancements in high-power, broadly tunable MWIR laser technology.
• The wide tuning range and high output power make this laser a promising candidate for spectroscopic applications requiring broad spectral coverage.