Continuous-wave interband cascade lasers operating above room temperature at λ = 4.7-5.6 μm

Area of Science:

• Semiconductor lasers
• Optoelectronics
• Quantum well devices

Background:

• Interband cascade lasers (ICLs) are crucial for mid-infrared (MIR) applications.
• Optimizing carrier balance in active regions is key to improving ICL performance.
• Previous methods struggled to achieve high operating temperatures and low thresholds in the 4.7-5.6 μm range.

Purpose of the Study:

• To enhance the performance of interband cascade lasers (ICLs) emitting at 4.7 and 5.6 μm.
• To investigate the impact of heavily doped injector regions on ICL performance.
• To achieve higher continuous wave (CW) operating temperatures and lower threshold power densities.

Main Methods:

• Fabrication of ICL ridges with specific dimensions (≈10 μm width, 4 mm length).
• Application of high-reflectivity back facets.
• Implementation of heavily doped injector regions to rebalance electron and hole concentrations in active quantum wells.

Main Results:

• Achieved maximum CW operating temperatures of 60°C (at 4.7 μm) and 48°C (at 5.6 μm).
• Demonstrated a threshold power density of ≈1 kW/cm² at 25°C.
• Observed a reduction in threshold power density by over an order of magnitude compared to state-of-the-art quantum cascade lasers in this spectral range.

Conclusions:

• Heavily doping injector regions is a highly effective strategy for improving ICL performance.
• The developed ICLs exhibit superior operating temperatures and efficiency for MIR applications.
• This advancement paves the way for more practical and efficient MIR laser sources.