Hollow metallic waveguides integrated with terahertz quantum cascade lasers

Area of Science:

• Optics and Photonics
• Semiconductor Devices
• Terahertz Technology

Background:

• Terahertz quantum cascade lasers (TQCLs) emit sub-wavelength plasmonic modes.
• Efficiently coupling and shaping TQCL emission is crucial for applications.
• Existing methods for beam shaping have limitations.

Purpose of the Study:

• To develop a compact, integrated system for improved terahertz beam emission.
• To investigate the monolithic integration of TQCLs with hollow metallic waveguides.
• To evaluate the beam shaping capabilities of this novel arrangement.

Main Methods:

• Monolithic integration of a copper pipe waveguide directly onto the TQCL end facet.
• Utilizing a double metal waveguide structure for efficient coupling.
• Theoretical modeling to predict and analyze mode behavior.
• Comparison with alternative beam shaping methods, such as silicon lenses.

Main Results:

• Significant improvement in far-field emission from sub-wavelength plasmonic modes.
• Preservation of the intrinsic performance characteristics of the terahertz quantum cascade laser.
• Demonstration of superior beam shaping compared to silicon hyper-hemispherical lenses.
• Theoretical model accurately predicted mode excitation, guiding alignment procedures.

Conclusions:

• Direct integration of hollow metallic waveguides offers a superior method for terahertz beam shaping.
• This approach enhances emission efficiency and maintains laser performance.
• Precise alignment is critical to avoid unwanted higher-order or mixed modes.