Watt-level, high wall plug efficiency, continuous-wave room temperature quantum cascade laser emitting at 7.7µm

Area of Science:

• Semiconductor Lasers
• Quantum Cascade Lasers
• Mid-Infrared Photonics

Background:

• Quantum cascade lasers (QCLs) are crucial for mid-infrared applications.
• Developing efficient and high-performance QCLs at room temperature remains a key challenge.
• Indium Phosphide (InP) based materials offer unique properties for optoelectronic devices.

Purpose of the Study:

• To report on a novel InP-based strain-balanced InGaAs/InAlAs quantum cascade laser.
• To achieve efficient laser emission at 7.7µm with high performance metrics.
• To investigate the impact of active region and waveguide design on laser performance.

Main Methods:

• Fabrication of a strain-balanced InGaAs/InAlAs quantum cascade laser structure.
• Utilizing a slightly-diagonal bound to continuum active region design with 50 stages.
• Optimization of active region and waveguide for reduced optical loss.
• Employing narrow ridge and buried ridge structures with diamond heatsinks for improved thermal management.

Main Results:

• Demonstrated a quantum cascade laser emitting at 7.7µm.
• Achieved a high wall-plug efficiency (WPE) of 9.08% and a low threshold current density of 1.09 kA/cm² in continuous-wave (CW) operation at 293K.
• Measured maximum output powers of 1.17W (CW) and 2.3W (pulsed) at 293K.
• Obtained a pure zero-order mode beam and a broad external-cavity tuning range (7.16µm–8.16µm).

Conclusions:

• The developed InP-based QCL exhibits excellent performance characteristics, including high efficiency and output power at room temperature.
• The optimized device design and thermal management strategies are effective in enhancing QCL performance.
• This work contributes to the advancement of mid-infrared laser technology for various applications.