Quantum cascade lasers with a tilted facet utilizing the inherent polarization purity

Area of Science:

• Optoelectronics
• Semiconductor Physics
• Laser Technology

Background:

• Quantum cascade lasers (QCLs) exhibit unique polarization properties.
• Intersubband selection rules dictate that QCLs emit purely TM-polarized light.
• Facet reflectivity is crucial for laser performance but often unoptimized in QCLs.

Purpose of the Study:

• To enhance light output power in QCLs by manipulating facet reflectivity.
• To investigate the effect of tilted facets on TM reflectivity and laser performance.
• To explore the role of the Brewster angle in TM reflectivity for QCLs.

Main Methods:

• Fabrication of QCLs with tilted front facets.
• Measurement of output power and slope efficiency for different facet angles.
• COMSOL simulations to analyze TM reflectivity and Brewster angle effects.

Main Results:

• Tilting the front facet reduces TM reflectivity, enhancing light output.
• A 12° facet angle increased peak output power by 31%.
• A 17° facet angle increased slope efficiency by 43%.

Conclusions:

• Tilted facets are an effective method for boosting QCL output power.
• Understanding and utilizing TM reflectivity, including Brewster angle phenomena, is key for QCL optimization.
• This technique offers a practical approach to improve QCL performance.