Terahertz quantum cascade lasers based on two-dimensional photonic crystal resonators

Area of Science:

• Optics and Photonics
• Semiconductor Lasers
• Terahertz Technology

Background:

• Quantum Cascade Lasers (QCLs) are crucial for generating THz radiation.
• Achieving high spectral control in surface-emitting THz QCLs remains a challenge.
• Photonic crystal cavities offer potential for mode control in lasers.

Purpose of the Study:

• To demonstrate high spectral control in surface-emitting THz Quantum Cascade Lasers.
• To investigate the role of a 2D photonic crystal cavity and metallic contact in laser performance.
• To analyze the light outcoupling mechanism and its effect on extraction efficiency.

Main Methods:

• Fabrication of THz QCLs incorporating a 2D photonic crystal cavity.
• Utilizing a perforated top metallic contact as an in-plane resonator.
• Employing a tight double-metal plasmonic waveguide for optical feedback.
• Characterization of optical far-field patterns and spectral properties.

Main Results:

• High spectral control was successfully demonstrated from the surface-emitting THz QCLs.
• The perforated metallic contact provided strong optical feedback without 3D cavity features.
• Observed deviations in far-field patterns from expected symmetry were noted.
• A metal surface plasmon mediated outcoupling mechanism was identified.

Conclusions:

• The 2D photonic crystal cavity design enables effective spectral control in THz QCLs.
• The perforated metallic contact design is a viable approach for strong optical feedback.
• The identified outcoupling mechanism influences both far-field patterns and extraction efficiency.